Implement Like / Tip a Memo

Adds the Memo like action (0x6d04) with optional author tip, a like/tip
page controller, heart icon + modal UI, and acceptance handlers for
specs/like-tip-memo.feature.

By coder.

acceptance/lib/handlers.js

@@ -26,10 +26,16 @@ const ReplyThreadPage = require('../../src/services/reply-thread-page')
 const MemoSetName = require('../../src/services/memo-set-name')
 const SetNamePage = require('../../src/services/set-name-page')
 const AccountPage = require('../../src/services/account-page')
+const MemoLike = require('../../src/services/memo-like')
+const LikeTipPage = require('../../src/services/like-tip-page')
 
 const MEMO_POST_PREFIX = MemoPost.MEMO_POST_PREFIX
 const MEMO_REPLY_PREFIX = MemoReply.MEMO_REPLY_PREFIX
 const MEMO_SET_NAME_PREFIX = MemoSetName.MEMO_SET_NAME_PREFIX
+const MEMO_LIKE_PREFIX = MemoLike.MEMO_LIKE_PREFIX
+
+// Default author address used by Gherkin steps that refer to "the author address".
+const AUTHOR_ADDRESS = 'bitcoincash:qz7v6ztvzu2f2xd2ww8pnx9vwk0g4ncvfvavktg0jc'
 
 // A fake wallet exposing the minimal-slp-wallet adapter surface the app uses.
 function makeWallet (address) {
@@ -40,9 +46,9 @@ function makeWallet (address) {
     getUtxos: async function () {
       return this.utxos
     },
-    sendOpReturn: async function (msg, prefix) {
+    sendOpReturn: async function (msg, prefix, bchOutput = []) {
       // Record the broadcast attempt, then fail if configured to do so.
-      this.broadcasts.push({ msg, prefix })
+      this.broadcasts.push({ msg, prefix, bchOutput })
       if (this.failWith) throw new Error(this.failWith)
       return 'aa'.repeat(32)
     }
@@ -86,14 +92,18 @@ function createWorld () {
   const memoPost = new MemoPost({ wallet, feed })
   const thread = makeThread()
   const memoReply = new MemoReply({ wallet, thread })
+  const memoLike = new MemoLike({ wallet, feed })
+
   const world = {
     wallet,
     feed,
     thread,
     memoPost,
     memoReply,
+    memoLike,
     currentPath: null,
-    menuOpen: false
+    menuOpen: false,
+    likedTxids: new Set()
   }
 
   // The New Post Page controller wraps the memo post behavior. Its navigate
@@ -111,6 +121,9 @@ function createWorld () {
     navigate: () => {}
   })
 
+  // The Like / Tip Page controller wraps the memo like behavior.
+  world.likeTipPage = new LikeTipPage({ memoLike })
+
   // The Set Name Page and Account Page controllers share a profile store so
   // a name set on one page is visible on the other.
   const profiles = makeProfiles()
@@ -136,6 +149,24 @@ function decodeReplyPayload (raw) {
   return { parentTxid, text }
 }
 
+// Decode a raw like payload back into the liked post txid (hex).
+function decodeLikeTxid (raw) {
+  return Buffer.from(raw).toString('hex')
+}
+
+// Resolve a literal value or a <parameter> placeholder from the example store.
+function resolveParam (value, example) {
+  const match = /^<([A-Za-z0-9_]+)>$/.exec(String(value).trim())
+  if (match) {
+    const param = match[1]
+    if (!(param in example)) {
+      throw new Error(`Missing example value for "${param}"`)
+    }
+    return example[param]
+  }
+  return String(value).trim()
+}
+
 // Handler registry. Each entry: { pattern, run }.
 // run receives (match, exampleStore, world, step).
 const handlers = [
@@ -562,6 +593,209 @@ const handlers = [
         throw new Error('Account page does not show a Set Name button.')
       }
     }
+  },
+  {
+    name: 'wallet has spendable balance',
+    pattern: /^the wallet has a spendable balance of (.+) sats$/,
+    run (m, example, world) {
+      const balance = parseInt(resolveParam(m[1], example), 10)
+      if (Number.isNaN(balance)) {
+        throw new Error(`Invalid balance value "${m[1]}"`)
+      }
+      world.wallet.utxos = [{ txid: 'utxo-for-balance', value: balance }]
+    }
+  },
+  {
+    name: 'post with txid authored by author address',
+    pattern: /^a post with the txid (.+) authored by the author address$/,
+    run (m, example, world) {
+      const txid = resolveParam(m[1], example)
+      const post = {
+        txid,
+        addr: AUTHOR_ADDRESS,
+        address: AUTHOR_ADDRESS,
+        text: 'A sample post',
+        likeCount: 0
+      }
+      world.feed.addPost(post)
+    }
+  },
+  {
+    name: 'post with txid authored by my address',
+    pattern: /^a post with the txid (.+) authored by my address$/,
+    run (m, example, world) {
+      const txid = resolveParam(m[1], example)
+      const myAddress = world.wallet.walletInfo.cashAddress
+      const post = {
+        txid,
+        addr: myAddress,
+        address: myAddress,
+        text: 'My own post',
+        likeCount: 0
+      }
+      world.feed.addPost(post)
+    }
+  },
+  {
+    name: 'click heart icon on post',
+    pattern: /^I click the heart icon on the post with txid (.+)$/,
+    run (m, example, world) {
+      const txid = resolveParam(m[1], example)
+      const post = world.feed.posts.find((p) => p.txid === txid)
+      const authorAddress = post ? post.addr : AUTHOR_ADDRESS
+      world.likeTipPage.open(txid, authorAddress)
+    }
+  },
+  {
+    name: 'like/tip modal opens for post',
+    pattern: /^a like\/tip modal opens for the post with txid (.+)$/,
+    run (m, example, world) {
+      const txid = resolveParam(m[1], example)
+      if (!world.likeTipPage.modalOpen) {
+        throw new Error('Expected like/tip modal to be open.')
+      }
+      if (world.likeTipPage.postTxid !== txid) {
+        throw new Error(`Expected like/tip modal for ${txid}, but got ${world.likeTipPage.postTxid}.`)
+      }
+    }
+  },
+  {
+    name: 'submit like without tip',
+    pattern: /^I submit the like without a tip$/,
+    async run (m, example, world) {
+      world.likeTipPage.setTip('')
+      const result = await world.likeTipPage.submit()
+      if (result.ok) {
+        world.likedTxids.add(world.likeTipPage.postTxid)
+      }
+    }
+  },
+  {
+    name: 'enter tip',
+    pattern: /^I enter a tip of (.+)$/,
+    run (m, example, world) {
+      world.likeTipPage.setTip(resolveParam(m[1], example))
+    }
+  },
+  {
+    name: 'submit like',
+    pattern: /^I submit the like$/,
+    async run (m, example, world) {
+      const result = await world.likeTipPage.submit()
+      if (result.ok) {
+        world.likedTxids.add(world.likeTipPage.postTxid)
+      }
+    }
+  },
+  {
+    name: 'broadcasts OP_RETURN with Memo like prefix',
+    pattern: /^the wallet broadcasts an OP_RETURN transaction with the Memo like prefix and the post txid (.+)$/,
+    run (m, example, world) {
+      const txid = resolveParam(m[1], example)
+      const broadcasts = world.wallet.broadcasts
+      if (!broadcasts.length) {
+        throw new Error('No OP_RETURN transaction was broadcast.')
+      }
+      const last = broadcasts[broadcasts.length - 1]
+      if (last.prefix !== MEMO_LIKE_PREFIX) {
+        throw new Error(`Expected Memo like prefix ${MEMO_LIKE_PREFIX}, got "${last.prefix}".`)
+      }
+      if (decodeLikeTxid(last.msg) !== txid) {
+        throw new Error(`Broadcast liked txid did not match ${txid}.`)
+      }
+    }
+  },
+  {
+    name: 'wallet sends no tip',
+    pattern: /^the wallet sends no tip$/,
+    run (m, example, world) {
+      const broadcasts = world.wallet.broadcasts
+      if (!broadcasts.length) {
+        throw new Error('No transaction was broadcast.')
+      }
+      const last = broadcasts[broadcasts.length - 1]
+      if (!Array.isArray(last.bchOutput) || last.bchOutput.length !== 0) {
+        throw new Error('Expected no tip output, but one was present.')
+      }
+    }
+  },
+  {
+    name: 'wallet sends tip to author',
+    pattern: /^the wallet sends a tip of (.+) to the author address$/,
+    run (m, example, world) {
+      const expectedTip = parseInt(resolveParam(m[1], example), 10)
+      if (Number.isNaN(expectedTip)) {
+        throw new Error(`Invalid tip value "${m[1]}"`)
+      }
+      const broadcasts = world.wallet.broadcasts
+      if (!broadcasts.length) {
+        throw new Error('No transaction was broadcast.')
+      }
+      const last = broadcasts[broadcasts.length - 1]
+      if (!Array.isArray(last.bchOutput) || last.bchOutput.length === 0) {
+        throw new Error('Expected a tip output, but none was present.')
+      }
+      const tipOutput = last.bchOutput[0]
+      if (tipOutput.amountSat !== expectedTip) {
+        throw new Error(`Expected tip ${expectedTip} sats, got ${tipOutput.amountSat}.`)
+      }
+      const post = world.feed.posts.find((p) => p.txid === world.likeTipPage.postTxid)
+      const expectedAddress = post ? post.addr : AUTHOR_ADDRESS
+      if (tipOutput.address !== expectedAddress) {
+        throw new Error(`Expected tip to ${expectedAddress}, got ${tipOutput.address}.`)
+      }
+    }
+  },
+  {
+    name: 'like count increases by one',
+    pattern: /^the like count on the post increases by one$/,
+    run (m, example, world) {
+      const postTxid = world.likeTipPage.postTxid
+      const post = world.feed.posts.find((p) => p.txid === postTxid)
+      if (!post) {
+        throw new Error(`Post ${postTxid} not found in feed.`)
+      }
+      if (post.likeCount !== 1) {
+        throw new Error(`Expected like count to be 1, got ${post.likeCount}.`)
+      }
+    }
+  },
+  {
+    name: 'heart icon shows as filled',
+    pattern: /^the heart icon on the post shows as filled$/,
+    run (m, example, world) {
+      const postTxid = world.likeTipPage.postTxid
+      if (!world.likedTxids.has(postTxid)) {
+        throw new Error(`Expected heart icon to be filled for ${postTxid}.`)
+      }
+    }
+  },
+  {
+    name: 'like/tip modal shows error containing text',
+    pattern: /^the like\/tip modal shows an error containing "(.+)"$/,
+    run (m, example, world) {
+      const expected = m[1]
+      const actual = world.likeTipPage.broadcastError || ''
+      if (!actual.includes(expected)) {
+        throw new Error(`Expected an error containing "${expected}", got "${actual}".`)
+      }
+    }
+  },
+  {
+    name: 'click cancel button',
+    pattern: /^I click the cancel button$/,
+    run (m, example, world) {
+      world.likeTipPage.close()
+    }
+  },
+  {
+    name: 'like/tip modal closes',
+    pattern: /^the like\/tip modal closes$/,
+    run (m, example, world) {
+      if (world.likeTipPage.modalOpen) {
+        throw new Error('Expected like/tip modal to be closed.')
+      }
+    }
   }
 ]
 

src/components/app-body/posts/index.js

@@ -131,6 +131,7 @@ function RecentPosts (props) {
                   key={post.txid}
                   post={post}
                   profiles={profiles}
+                  wallet={appData?.wallet}
                   onReplyClick={() => openThread(post.txid)}
                   showFooterMeta
                 />

src/components/post-feed/like-button.js

@@ -0,0 +1,37 @@
+/*
+  Like button for a post (heart icon + count).
+
+  The icon is filled when the post has been liked in the current session and
+  outlined otherwise. The count is displayed next to the icon.
+*/
+
+import React from 'react'
+import { FontAwesomeIcon } from '@fortawesome/react-fontawesome'
+import { faHeart as faHeartSolid } from '@fortawesome/free-solid-svg-icons'
+import { faHeart as faHeartRegular } from '@fortawesome/free-regular-svg-icons'
+
+import './post-feed.css'
+
+function LikeButton ({ count = 0, liked = false, onClick }) {
+  const label = count === 1 ? '1 like' : `${count} likes`
+  const icon = liked ? faHeartSolid : faHeartRegular
+  const className = [
+    'post-like-button',
+    liked ? 'post-like-button-liked' : ''
+  ].filter(Boolean).join(' ')
+
+  return (
+    <button
+      type='button'
+      className={className}
+      aria-label={label}
+      title={label}
+      onClick={onClick}
+    >
+      <FontAwesomeIcon icon={icon} className='post-like-button-icon' />
+      <span className='post-like-button-count'>{count}</span>
+    </button>
+  )
+}
+
+export default LikeButton

src/components/post-feed/like-tip-modal.js

@@ -0,0 +1,133 @@
+/*
+  Like / Tip modal for a post.
+
+  Lets the user submit a Memo like (0x6d04) with an optional satoshi tip to the
+  post author. The wallet and target post are injected through props. Errors
+  from validation, dust/maximum/balance checks, and broadcast failures are
+  surfaced in the modal body.
+*/
+
+import React, { useState, useEffect } from 'react'
+import { Modal, Form, Button } from 'react-bootstrap'
+
+import MemoLike from '../../services/memo-like'
+import LikeTipPage from '../../services/like-tip-page'
+import { getDisplayName } from './post-display'
+import './post-feed.css'
+
+function formatError (result) {
+  if (!result || result.ok) return ''
+  return result.message || ''
+}
+
+function LikeTipModal ({ show, post, wallet, profiles = {}, onHide, onSuccess }) {
+  const [tip, setTip] = useState('')
+  const [error, setError] = useState('')
+  const [submitting, setSubmitting] = useState(false)
+
+  const displayName = post ? getDisplayName(post.addr, profiles) : ''
+
+  // Reset state whenever the modal is shown and check the wallet balance.
+  useEffect(() => {
+    if (!show || !post || !wallet) {
+      setTip('')
+      setError('')
+      setSubmitting(false)
+      return
+    }
+
+    setTip('')
+    setError('')
+    setSubmitting(false)
+
+    const memoLike = new MemoLike({ wallet })
+    const page = new LikeTipPage({ memoLike })
+    const result = page.open(post.txid, post.addr)
+    if (!result.ok) {
+      setError(formatError(result))
+    }
+  }, [show, post, wallet])
+
+  async function handleSubmit () {
+    if (!post || !wallet) return
+    setError('')
+    setSubmitting(true)
+
+    try {
+      const memoLike = new MemoLike({ wallet })
+      const page = new LikeTipPage({ memoLike })
+      page.open(post.txid, post.addr)
+      page.setTip(tip)
+
+      const result = await page.submit()
+      if (result.ok) {
+        setTip('')
+        if (typeof onSuccess === 'function') {
+          onSuccess()
+        }
+      } else {
+        setError(formatError(result))
+      }
+    } catch (submitErr) {
+      setError(submitErr.message)
+    } finally {
+      setSubmitting(false)
+    }
+  }
+
+  function handleCancel () {
+    setTip('')
+    setError('')
+    onHide()
+  }
+
+  return (
+    <Modal show={show} onHide={handleCancel} centered>
+      <Modal.Header closeButton>
+        <Modal.Title>Like / Tip</Modal.Title>
+      </Modal.Header>
+
+      <Modal.Body>
+        {post && (
+          <p className='like-tip-modal-target'>
+            Like the post by <strong>{displayName}</strong>
+          </p>
+        )}
+
+        <Form onSubmit={(e) => { e.preventDefault(); handleSubmit() }}>
+          <Form.Group controlId='like-tip-amount' className='mb-3'>
+            <Form.Label>Tip (satoshis, optional)</Form.Label>
+            <Form.Control
+              type='number'
+              min='0'
+              step='1'
+              placeholder='0'
+              value={tip}
+              onChange={(e) => setTip(e.target.value)}
+              disabled={submitting || !!error}
+            />
+          </Form.Group>
+        </Form>
+
+        {error && (
+          <p className='like-tip-modal-error text-danger'>{error}</p>
+        )}
+      </Modal.Body>
+
+      <Modal.Footer>
+        <Button variant='secondary' onClick={handleCancel}>
+          Cancel
+        </Button>
+        <Button
+          variant='primary'
+          onClick={handleSubmit}
+          disabled={submitting || !!error || !post || !wallet}
+        >
+          {submitting ? 'Liking...' : 'Like'}
+        </Button>
+      </Modal.Footer>
+    </Modal>
+  )
+}
+
+export default LikeTipModal

src/components/post-feed/post-feed-item.js

@@ -2,12 +2,14 @@
   Instagram-style post card for feed and thread views.
 */
 
-import React from 'react'
+import React, { useState } from 'react'
 import { Link } from 'react-router-dom'
 
 import AppUtil from '../../util'
 import PostReplyCount from '../post-reply-count'
 import PostThreadAvatar from '../post-thread-modal/post-thread-avatar'
+import LikeButton from './like-button'
+import LikeTipModal from './like-tip-modal'
 import {
   formatRelativeSeen,
   getDisplayName,
@@ -21,14 +23,20 @@ function PostFeedItem ({
   post,
   profile = {},
   profiles = {},
+  wallet,
   onReplyClick,
   showRepliedLabel = false,
   showFooterMeta = false,
   showReplyCount = true,
+  showLikeButton = true,
   embedded = false
 }) {
   if (!post) return null
 
+  const [liked, setLiked] = useState(false)
+  const [likeCount, setLikeCount] = useState(post.likeCount || 0)
+  const [showLikeModal, setShowLikeModal] = useState(false)
+
   const displayName = getDisplayName(post.addr, profiles)
 
   const hasCustomName = Boolean(
@@ -46,6 +54,20 @@ function PostFeedItem ({
     appUtil.copyToClipboard(post.txid)
   }
 
+  const handleLikeClick = () => {
+    setShowLikeModal(true)
+  }
+
+  const handleLikeSuccess = () => {
+    setLiked(true)
+    setLikeCount((count) => count + 1)
+    setShowLikeModal(false)
+  }
+
+  const handleLikeModalHide = () => {
+    setShowLikeModal(false)
+  }
+
   return (
     <Wrapper
       className={[
@@ -117,12 +139,21 @@ function PostFeedItem ({
         </p>
       </div>
 
-      {showReplyCount && (
+      {(showReplyCount || showLikeButton) && (
         <div className='posts-feed-item-actions'>
-          <PostReplyCount
-            count={post.replyCount ?? 0}
-            onClick={onReplyClick}
-          />
+          {showLikeButton && (
+            <LikeButton
+              count={likeCount}
+              liked={liked}
+              onClick={handleLikeClick}
+            />
+          )}
+          {showReplyCount && (
+            <PostReplyCount
+              count={post.replyCount ?? 0}
+              onClick={onReplyClick}
+            />
+          )}
         </div>
       )}
 
@@ -147,6 +178,15 @@ function PostFeedItem ({
           </button>
         </footer>
       )}
+
+      <LikeTipModal
+        show={showLikeModal}
+        post={post}
+        wallet={wallet}
+        profiles={profiles}
+        onHide={handleLikeModalHide}
+        onSuccess={handleLikeSuccess}
+      />
     </Wrapper>
   )
 }

src/components/post-feed/post-feed.css

@@ -603,3 +603,62 @@
     padding: 0 0.75rem;
   }
 }
+
+.post-like-button {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  gap: 6px;
+
+  min-height: 32px;
+  padding: 4px 0;
+
+  color: var(--ig-text);
+  background: transparent;
+
+  border: 0;
+  border-radius: 0;
+
+  font-size: 13px;
+  font-weight: 600;
+  line-height: 18px;
+  text-decoration: none;
+
+  cursor: pointer;
+
+  transition:
+    opacity 0.15s ease,
+    color 0.15s ease;
+}
+
+.post-like-button:hover {
+  color: var(--ig-danger);
+  background: transparent;
+  border: 0;
+  box-shadow: none;
+  transform: none;
+  opacity: 0.65;
+}
+
+.post-like-button-liked,
+.post-like-button-liked:hover {
+  color: var(--ig-danger);
+  opacity: 1;
+}
+
+.post-like-button-icon {
+  font-size: 18px;
+}
+
+.post-like-button-count {
+  min-width: 1.2em;
+}
+
+.like-tip-modal-target {
+  margin-bottom: 1rem;
+}
+
+.like-tip-modal-error {
+  margin: 0;
+  font-size: 0.95rem;
+}

src/components/post-thread-modal/index.js

@@ -107,7 +107,7 @@ function PostThreadModal ({ show, txid, onHide, wallet, profiles: externalProfil
 
         {!loading && !error && thread && (
           <>
-            <PostThreadNode post={thread} profiles={profiles} isRoot />
+            <PostThreadNode post={thread} profiles={profiles} wallet={wallet} isRoot />
             <ReplyThreadForm
               parentTxid={txid}
               rootPost={thread}
@@ -120,6 +120,7 @@ function PostThreadModal ({ show, txid, onHide, wallet, profiles: externalProfil
                 key={reply.txid}
                 post={reply}
                 profiles={profiles}
+                wallet={wallet}
               />
             ))}
           </>

src/components/post-thread-modal/post-thread-node.js

@@ -6,7 +6,7 @@ import React from 'react'
 
 import PostFeedItem from '../post-feed/post-feed-item'
 
-function PostThreadNode ({ post, profiles = {}, depth = 0, isRoot = false }) {
+function PostThreadNode ({ post, profiles = {}, wallet, depth = 0, isRoot = false }) {
   if (!post) return null
 
   const profile = profiles[post.addr] || {}
@@ -21,6 +21,7 @@ function PostThreadNode ({ post, profiles = {}, depth = 0, isRoot = false }) {
           post={post}
           profile={profile}
           profiles={profiles}
+          wallet={wallet}
           showRepliedLabel={!isRoot}
           showReplyCount={false}
           embedded
@@ -30,6 +31,7 @@ function PostThreadNode ({ post, profiles = {}, depth = 0, isRoot = false }) {
             key={reply.txid}
             post={reply}
             profiles={profiles}
+            wallet={wallet}
             depth={depth + 1}
           />
         ))}

src/services/hex.js

@@ -0,0 +1,28 @@
+/*
+  Hex encoding helpers used by Memo protocol actions.
+
+  A Bitcoin Cash transaction id is a 32-byte value encoded as a 64-character
+  hex string. Memo actions like replies and likes need to embed that txid in
+  the OP_RETURN payload as raw bytes, so this module provides a small,
+  testable conversion helper.
+*/
+
+// Decode a hex string into a Uint8Array of the requested byte length.
+// The label parameter customizes error messages for the caller's context.
+function hexToBytes (hex, byteLength = 32, label = 'Value') {
+  if (typeof hex !== 'string' || hex.length !== byteLength * 2) {
+    throw new Error(`${label} must be a ${byteLength * 2}-character hex string.`)
+  }
+
+  const bytes = new Uint8Array(byteLength)
+  for (let i = 0; i < hex.length; i += 2) {
+    const byte = parseInt(hex.substr(i, 2), 16)
+    if (Number.isNaN(byte)) {
+      throw new Error(`${label} must be a valid hex string.`)
+    }
+    bytes[i / 2] = byte
+  }
+  return bytes
+}
+
+module.exports = { hexToBytes }

src/services/like-tip-page.js

@@ -0,0 +1,106 @@
+/*
+  Like / Tip page behavior: open a modal for a post, validate an optional tip,
+  and submit a Memo like (0x6d04) with or without a tip.
+
+  This is the testable controller behind the React like/tip modal. It wraps
+  the Memo like behavior (src/services/memo-like.js) and adds page-level
+  concerns: holding the target post txid, holding the tip input as a string,
+  surfacing validation/dust/maximum/balance errors, and closing the modal on
+  success or cancellation.
+
+  The memoLike and modal state concerns are injected so this module stays free
+  of UI/network concerns; environmentally unsuitable I/O lives behind those
+  small adapter boundaries.
+*/
+
+const PageController = require('./page-controller')
+
+class LikeTipPage extends PageController {
+  constructor (deps = {}) {
+    super(deps)
+    this.memoLike = deps.memoLike || null
+    this.tipping = false
+    this.modalOpen = false
+    this.postTxid = deps.postTxid || null
+    this.authorAddress = deps.authorAddress || ''
+    this.successPath = null
+    this.validationCodes = ['like_validation', 'like_dust', 'like_maximum', 'like_balance', 'like_empty_balance']
+  }
+
+  // Open the like/tip modal for a post and check that the wallet has enough
+  // spendable balance to cover fees. Returns a result object.
+  open (postTxid, authorAddress) {
+    this.postTxid = postTxid
+    this.authorAddress = authorAddress
+    this.modalOpen = true
+    this.submitError = null
+    this.broadcastError = null
+
+    if (!this.memoLike) {
+      this.submitError = 'like_validation'
+      this.broadcastError = 'Like requires a memo like handler.'
+      return { ok: false, error: this.submitError, message: this.broadcastError }
+    }
+
+    try {
+      const spendable = this.memoLike.getSpendableSats()
+      if (spendable < this.memoLike.dustLimit) {
+        const err = new Error('add BCH to your wallet before liking a post.')
+        err.code = 'like_empty_balance'
+        throw err
+      }
+    } catch (err) {
+      return this._handleSubmitFailure(err)
+    }
+
+    return { ok: true }
+  }
+
+  // Close the modal and reset input/errors.
+  close () {
+    this.modalOpen = false
+    this.submitError = null
+    this.broadcastError = null
+    this.input = ''
+  }
+
+  // Set the tip amount as a raw string. The string form is validated on submit
+  // so non-numeric or decimal input can be rejected.
+  setTip (tipStr) {
+    this.setInput(tipStr)
+  }
+
+  // Set the in-flight tipping flag.
+  _setBusy (value) {
+    this.tipping = value
+  }
+
+  // Parse a non-empty tip string into an integer number of satoshis.
+  _parseTip (input) {
+    if (input === '' || input === null || input === undefined) return 0
+    if (!/^\d+$/.test(String(input))) {
+      const err = new Error('Tip must be a valid number of satoshis.')
+      err.code = 'like_validation'
+      throw err
+    }
+    return parseInt(input, 10)
+  }
+
+  // Run the memo like action for the current post and tip.
+  async _perform (input) {
+    if (!this.memoLike) {
+      throw new Error('Like requires a memo like handler.')
+    }
+    const tipSats = this._parseTip(input)
+    return this.memoLike.like(this.postTxid, tipSats, this.authorAddress)
+  }
+
+  // Surface the real error message for every failure, including local
+  // validation failures, so the like/tip modal can display it.
+  _handleSubmitFailure (err) {
+    this.broadcastError = err.message || String(err)
+    return super._handleSubmitFailure(err)
+  }
+}
+
+module.exports = LikeTipPage

src/services/memo-like.js

@@ -0,0 +1,167 @@
+/*
+  Memo like/tip behavior: compose, validate, and broadcast a Memo "like"
+  action with an optional tip.
+
+  A Memo like is an OP_RETURN Bitcoin Cash transaction carrying the Memo like
+  protocol prefix (0x6d04) followed by the liked post transaction hash (32
+  bytes). When the user adds a tip, an additional P2PKH output sending the tip
+  amount to the post author's address is included in the same transaction.
+
+  Broadcasting is done through a wallet that exposes the minimal-slp-wallet
+  adapter surface (walletInfo, getUtxos(), sendOpReturn(msg, prefix, bchOutput)).
+
+  The wallet and feed are injected so this module stays testable and free of
+  network/UI concerns; environmentally unsuitable I/O lives behind those small
+  adapter boundaries.
+
+  Constants
+    MEMO_LIKE_PREFIX  : hex prefix for the Memo "like" action (0x6d04)
+    DUST_LIMIT_SATS   : smallest non-dust BCH output (3000 sats)
+    MAX_TIP_SATS      : sanity maximum for a single tip (100000000 sats = 1 BCH)
+    PARENT_TXID_BYTES : liked post txid size in bytes (32)
+*/
+
+const MemoAction = require('./memo-action')
+const { hexToBytes } = require('./hex')
+
+const MEMO_LIKE_PREFIX = '6d04'
+const DUST_LIMIT_SATS = 3000
+const MAX_TIP_SATS = 100000000
+const PARENT_TXID_BYTES = 32
+
+class MemoLike extends MemoAction {
+  static config = {
+    prefix: MEMO_LIKE_PREFIX,
+    walletRequiredMsg: 'Memo like requires a wallet.',
+    lengthMessage: 'Post txid must be a 64-character hex string.',
+    emptyMessage: 'Post txid must be a 64-character hex string.',
+    lengthCode: 'like_validation',
+    validationCode: 'like_validation'
+  }
+
+  constructor (deps = {}) {
+    super(deps)
+    this.feed = deps.feed
+    this.dustLimit = deps.dustLimit || DUST_LIMIT_SATS
+    this.maxTip = deps.maxTip || MAX_TIP_SATS
+  }
+
+  // Validate a candidate post txid.
+  // Returns { ok: true } or throws a typed validation error.
+  validate (postTxid) {
+    try {
+      hexToBytes(postTxid, PARENT_TXID_BYTES, 'Post txid')
+      return { ok: true }
+    } catch (err) {
+      const validationErr = new Error(err.message)
+      validationErr.code = this.validationCode
+      throw validationErr
+    }
+  }
+
+  // Validate an optional tip amount against the dust limit, hard maximum, and
+  // the wallet's spendable balance.
+  validateTip (tipSats, spendableSats) {
+    if (!Number.isInteger(tipSats) || tipSats < 0) {
+      const err = new Error('Tip must be a valid number of satoshis.')
+      err.code = 'like_validation'
+      throw err
+    }
+
+    if (tipSats > 0 && tipSats < this.dustLimit) {
+      const err = new Error(`Tip is below the dust limit of ${this.dustLimit} sats.`)
+      err.code = 'like_dust'
+      throw err
+    }
+
+    if (tipSats > this.maxTip) {
+      const err = new Error(`Tip exceeds the maximum of ${this.maxTip} sats.`)
+      err.code = 'like_maximum'
+      throw err
+    }
+
+    if (tipSats > spendableSats) {
+      const err = new Error('Tip exceeds the spendable balance.')
+      err.code = 'like_balance'
+      throw err
+    }
+
+    return { ok: true }
+  }
+
+  // Sum the wallet's spendable UTXOs. Tolerates the common value field names
+  // used by different wallet adapters.
+  getSpendableSats () {
+    if (!this.wallet) return 0
+    const utxos = this.wallet.utxos || []
+    return utxos.reduce((sum, u) => {
+      const value = u.value ?? u.satoshis ?? u.amount ?? 0
+      return sum + value
+    }, 0)
+  }
+
+  // Compose and broadcast a Memo like for the given post txid.
+  // tipSats is optional (defaults to 0). authorAddress is required when
+  // tipSats is greater than 0.
+  // Resolves with the transaction id, or rejects with a typed error.
+  async like (postTxid, tipSats = 0, authorAddress = '') {
+    this.validate(postTxid)
+
+    if (!this.wallet) {
+      throw new Error(this.walletRequiredMsg)
+    }
+
+    await this.wallet.getUtxos()
+
+    const spendable = this.getSpendableSats()
+    if (spendable < this.dustLimit) {
+      const err = new Error('add BCH to your wallet before liking a post.')
+      err.code = 'like_empty_balance'
+      throw err
+    }
+
+    this.validateTip(tipSats, spendable)
+
+    if (tipSats > 0 && (!authorAddress || typeof authorAddress !== 'string')) {
+      const err = new Error('Tip requires an author address.')
+      err.code = 'like_validation'
+      throw err
+    }
+
+    const raw = hexToBytes(postTxid, PARENT_TXID_BYTES, 'Post txid')
+    const bchOutput = tipSats > 0
+      ? [{ address: authorAddress, amountSat: tipSats }]
+      : []
+
+    const txid = await this.wallet.sendOpReturn(raw, this.prefix, bchOutput)
+
+    this.reflect(txid, postTxid, tipSats)
+
+    return txid
+  }
+
+  // Record the new like on the injected feed when one is present.
+  reflect (txid, postTxid, tipSats) {
+    if (this.feed && typeof this.feed.addLike === 'function') {
+      this.feed.addLike({
+        txid,
+        postTxid,
+        address: this.wallet.walletInfo.cashAddress,
+        tipSats
+      })
+    }
+
+    if (this.feed && Array.isArray(this.feed.posts)) {
+      const post = this.feed.posts.find((p) => p.txid === postTxid)
+      if (post) {
+        post.likeCount = (post.likeCount || 0) + 1
+      }
+    }
+  }
+}
+
+MemoLike.MEMO_LIKE_PREFIX = MEMO_LIKE_PREFIX
+MemoLike.DUST_LIMIT_SATS = DUST_LIMIT_SATS
+MemoLike.MAX_TIP_SATS = MAX_TIP_SATS
+
+module.exports = MemoLike

src/services/memo-reply.js

@@ -18,6 +18,7 @@
 
 const MemoAction = require('./memo-action')
 const { byteLength } = require('./utf8')
+const { hexToBytes } = require('./hex')
 
 const MEMO_REPLY_PREFIX = '6d03'
 const MAX_REPLY_BYTES = 184
@@ -82,7 +83,7 @@ class MemoReply extends MemoAction {
 // Build the raw OP_RETURN message payload for a reply.
 // The protocol wire format is: <parent txid 32 bytes><reply text UTF-8 bytes>.
 function buildReplyPayload (parentTxid, message) {
-  const parentBytes = hexToBytes(parentTxid)
+  const parentBytes = hexToBytes(parentTxid, PARENT_TXID_BYTES, 'Parent txid')
   const textBytes = new TextEncoder().encode(message)
   const raw = new Uint8Array(parentBytes.length + textBytes.length)
   raw.set(parentBytes, 0)
@@ -90,22 +91,6 @@ function buildReplyPayload (parentTxid, message) {
   return raw
 }
 
-// Decode a 64-character hex transaction id into 32 raw bytes.
-function hexToBytes (hex) {
-  if (typeof hex !== 'string' || hex.length !== PARENT_TXID_BYTES * 2) {
-    throw new Error('Parent txid must be a 64-character hex string.')
-  }
-  const bytes = new Uint8Array(PARENT_TXID_BYTES)
-  for (let i = 0; i < hex.length; i += 2) {
-    const byte = parseInt(hex.substr(i, 2), 16)
-    if (Number.isNaN(byte)) {
-      throw new Error('Parent txid must be a valid hex string.')
-    }
-    bytes[i / 2] = byte
-  }
-  return bytes
-}
-
 MemoReply.MEMO_REPLY_PREFIX = MEMO_REPLY_PREFIX
 MemoReply.MAX_REPLY_BYTES = MAX_REPLY_BYTES
 

src/services/optimistic-reply.js

@@ -1,5 +1,4 @@
 
-
 // Build the optimistic reply object used by the reply form for immediate
 // thread rendering before the thread is refreshed from the network. This is a
 // pure data-shaping function so the reply object shape is unit-testable and

test/helpers/fake-wallet.js

@@ -6,20 +6,28 @@
 // sendOpReturn throw.
 function fakeWallet ({
   cashAddress = 'bitcoincash:qqlrzp23w08434twmvr4fxw672whkjy0py26r63g3d',
-  utxos = [{ txid: 'utxo1' }],
+  utxos = [{ txid: 'utxo1', value: 100000 }],
   txid = 'fake-txid'
 } = {}) {
   const broadcasts = []
+  const sends = []
   const wallet = {
     walletInfo: { cashAddress },
+    utxos,
     getUtxos: async () => utxos,
-    sendOpReturn: async function (msg, prefix) {
-      broadcasts.push({ msg, prefix })
+    sendOpReturn: async function (msg, prefix, bchOutput = []) {
+      broadcasts.push({ msg, prefix, bchOutput })
+      if (this.failWith) throw new Error(this.failWith)
+      return txid
+    },
+    send: async function (receivers) {
+      sends.push(receivers)
       if (this.failWith) throw new Error(this.failWith)
       return txid
     }
   }
   wallet.broadcasts = broadcasts
+  wallet.sends = sends
   return wallet
 }
 

test/unit/like-tip-page.test.js

@@ -0,0 +1,230 @@
+/*
+  Unit tests for the Like / Tip page behavior slice
+  (src/services/like-tip-page.js).
+
+  These tests express the page-level behavior described by
+  specs/like-tip-memo.feature:
+    - opening the modal for a post checks the wallet balance.
+    - submitting a like without a tip broadcasts the Memo like action.
+    - submitting a like with a tip broadcasts the action and the tip.
+    - invalid, dust, maximum, and balance errors are surfaced.
+*/
+
+'use strict'
+
+const test = require('node:test')
+const assert = require('node:assert/strict')
+
+const LikeTipPage = require('../../src/services/like-tip-page')
+const MemoLike = require('../../src/services/memo-like')
+const { fakeWallet } = require('../helpers/fake-wallet')
+
+const POST_TXID = 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'
+const AUTHOR_ADDRESS = 'bitcoincash:qz7v6ztvzu2f2xd2ww8pnx9vwk0g4ncvfvavktg0jc'
+const MY_ADDRESS = 'bitcoincash:qqlrzp23w08434twmvr4fxw672whkjy0py26r63g3d'
+
+function build () {
+  const wallet = fakeWallet({ cashAddress: MY_ADDRESS, utxos: [{ txid: 'u1', value: 100000 }] })
+  const feed = { posts: [], likes: [], addLike: (l) => feed.likes.push(l) }
+  const memoLike = new MemoLike({ wallet, feed })
+  const page = new LikeTipPage({ memoLike })
+  return { wallet, feed, memoLike, page }
+}
+
+test('opening the modal sets the target post and author', () => {
+  const { page } = build()
+
+  const result = page.open(POST_TXID, AUTHOR_ADDRESS)
+
+  assert.equal(result.ok, true)
+  assert.equal(page.modalOpen, true)
+  assert.equal(page.postTxid, POST_TXID)
+  assert.equal(page.authorAddress, AUTHOR_ADDRESS)
+})
+
+test('opening the modal with insufficient balance surfaces an add-BCH error', () => {
+  const wallet = fakeWallet({ cashAddress: MY_ADDRESS, utxos: [] })
+  const memoLike = new MemoLike({ wallet })
+  const page = new LikeTipPage({ memoLike })
+
+  const result = page.open(POST_TXID, AUTHOR_ADDRESS)
+
+  assert.equal(result.ok, false)
+  assert.equal(result.error, 'like_empty_balance')
+  assert.equal(page.submitError, 'like_empty_balance')
+  assert.match(page.broadcastError, /add BCH/i)
+  assert.equal(page.modalOpen, true)
+})
+
+test('opening the modal without a memo-like handler surfaces an error', () => {
+  const page = new LikeTipPage({})
+
+  const result = page.open(POST_TXID, AUTHOR_ADDRESS)
+
+  assert.equal(result.ok, false)
+  assert.equal(result.error, 'like_validation')
+  assert.match(page.broadcastError, /memo like/i)
+})
+
+test('closing the modal resets input and errors', () => {
+  const { page } = build()
+  page.open(POST_TXID, AUTHOR_ADDRESS)
+  page.setTip('5000')
+  page.submitError = 'like_dust'
+  page.broadcastError = 'some error'
+
+  page.close()
+
+  assert.equal(page.modalOpen, false)
+  assert.equal(page.input, '')
+  assert.equal(page.submitError, null)
+  assert.equal(page.broadcastError, null)
+})
+
+test('submitting a pure like broadcasts the Memo like prefix', async () => {
+  const { wallet, page } = build()
+  page.open(POST_TXID, AUTHOR_ADDRESS)
+
+  const result = await page.submit()
+
+  assert.equal(result.ok, true)
+  assert.equal(page.tipping, false)
+  assert.equal(wallet.broadcasts.length, 1)
+  assert.equal(wallet.broadcasts[0].prefix, '6d04')
+  assert.deepEqual(wallet.broadcasts[0].bchOutput, [])
+})
+
+test('submitting a like with a tip broadcasts the prefix and the tip output', async () => {
+  const { wallet, page } = build()
+  page.open(POST_TXID, AUTHOR_ADDRESS)
+  page.setTip('3000')
+
+  const result = await page.submit()
+
+  assert.equal(result.ok, true)
+  assert.equal(wallet.broadcasts.length, 1)
+  assert.equal(wallet.broadcasts[0].prefix, '6d04')
+  assert.deepEqual(wallet.broadcasts[0].bchOutput, [{ address: AUTHOR_ADDRESS, amountSat: 3000 }])
+})
+
+test('submitting a like on a post authored by the wallet works without a tip', async () => {
+  const { wallet, page } = build()
+  page.open(POST_TXID, MY_ADDRESS)
+
+  const result = await page.submit()
+
+  assert.equal(result.ok, true)
+  assert.equal(wallet.broadcasts.length, 1)
+  assert.equal(wallet.broadcasts[0].prefix, '6d04')
+})
+
+test('submitting with a non-numeric tip is rejected', async () => {
+  const { wallet, page } = build()
+  page.open(POST_TXID, AUTHOR_ADDRESS)
+  page.setTip('abc')
+
+  const result = await page.submit()
+
+  assert.equal(result.ok, false)
+  assert.equal(result.error, 'like_validation')
+  assert.equal(page.submitError, 'like_validation')
+  assert.match(page.broadcastError, /valid number/i)
+  assert.equal(wallet.broadcasts.length, 0)
+})
+
+test('submitting with a decimal tip string is rejected', async () => {
+  const { wallet, page } = build()
+  page.open(POST_TXID, AUTHOR_ADDRESS)
+  page.setTip('1.5')
+
+  const result = await page.submit()
+
+  assert.equal(result.ok, false)
+  assert.equal(result.error, 'like_validation')
+  assert.equal(wallet.broadcasts.length, 0)
+})
+
+test('submitting with a dust tip is rejected', async () => {
+  const { wallet, page } = build()
+  page.open(POST_TXID, AUTHOR_ADDRESS)
+  page.setTip('2999')
+
+  const result = await page.submit()
+
+  assert.equal(result.ok, false)
+  assert.equal(result.error, 'like_dust')
+  assert.equal(wallet.broadcasts.length, 0)
+})
+
+test('submitting with a tip above the maximum is rejected', async () => {
+  const wallet = fakeWallet({ cashAddress: MY_ADDRESS, utxos: [{ txid: 'u1', value: 150000000 }] })
+  const memoLike = new MemoLike({ wallet })
+  const page = new LikeTipPage({ memoLike })
+  page.open(POST_TXID, AUTHOR_ADDRESS)
+  page.setTip('100000001')
+
+  const result = await page.submit()
+
+  assert.equal(result.ok, false)
+  assert.equal(result.error, 'like_maximum')
+  assert.match(page.broadcastError, /maximum/i)
+  assert.equal(wallet.broadcasts.length, 0)
+})
+
+test('submitting with a tip above the spendable balance is rejected', async () => {
+  const wallet = fakeWallet({ cashAddress: MY_ADDRESS, utxos: [{ txid: 'u1', value: 30000 }] })
+  const memoLike = new MemoLike({ wallet })
+  const page = new LikeTipPage({ memoLike })
+  page.open(POST_TXID, AUTHOR_ADDRESS)
+  page.setTip('35000')
+
+  const result = await page.submit()
+
+  assert.equal(result.ok, false)
+  assert.equal(result.error, 'like_balance')
+  assert.match(page.broadcastError, /spendable/i)
+  assert.equal(wallet.broadcasts.length, 0)
+})
+
+test('tipping flag is true while a submit is in flight and false once it settles', async () => {
+  const { wallet, page } = build()
+  page.open(POST_TXID, AUTHOR_ADDRESS)
+
+  let resolveSend
+  wallet.sendOpReturn = async () => new Promise((resolve) => { resolveSend = resolve })
+
+  assert.equal(page.tipping, false)
+  const pending = page.submit()
+  assert.equal(page.tipping, true)
+
+  await new Promise((resolve) => setImmediate(resolve))
+  assert.equal(typeof resolveSend, 'function')
+  resolveSend('in-flight-txid')
+  await pending
+  assert.equal(page.tipping, false)
+})
+
+test('submitting without a memo-like handler reports an error', async () => {
+  const page = new LikeTipPage({})
+  page.open(POST_TXID, AUTHOR_ADDRESS)
+
+  const result = await page.submit()
+
+  assert.equal(result.ok, false)
+  assert.equal(page.submitError, 'broadcast')
+  assert.match(page.broadcastError, /memo like/i)
+})
+
+test('a failed broadcast surfaces the real error', async () => {
+  const wallet = fakeWallet({ cashAddress: MY_ADDRESS })
+  wallet.failWith = 'Insufficient balance'
+  const memoLike = new MemoLike({ wallet })
+  const page = new LikeTipPage({ memoLike })
+  page.open(POST_TXID, AUTHOR_ADDRESS)
+
+  const result = await page.submit()
+
+  assert.equal(result.ok, false)
+  assert.equal(page.submitError, 'broadcast')
+  assert.match(page.broadcastError, /Insufficient balance/)
+})

test/unit/memo-like.test.js

@@ -0,0 +1,261 @@
+/*
+  Unit tests for the Memo like/tip behavior slice (src/services/memo-like.js).
+
+  These tests express the observable behavior described by
+  specs/like-tip-memo.feature:
+    - a valid like broadcasts an OP_RETURN transaction carrying the Memo like
+      prefix (0x6d04) and the post txid bytes; an optional tip is included as a
+      BCH output to the author address.
+    - an invalid/non-integer tip is rejected with a validation error.
+    - a tip below the dust limit is rejected.
+    - a tip above the hard maximum is rejected.
+    - a tip above the spendable balance is rejected.
+    - a wallet without spendable balance cannot like.
+*/
+
+'use strict'
+
+const test = require('node:test')
+const assert = require('node:assert/strict')
+
+const MemoLike = require('../../src/services/memo-like')
+const { fakeWallet } = require('../helpers/fake-wallet')
+
+const POST_TXID = 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'
+const AUTHOR_ADDRESS = 'bitcoincash:qz7v6ztvzu2f2xd2ww8pnx9vwk0g4ncvfvavktg0jc'
+const MY_ADDRESS = 'bitcoincash:qqlrzp23w08434twmvr4fxw672whkjy0py26r63g3d'
+
+// A fake feed that records likes and exposes posts keyed by txid.
+function fakeFeed (posts = []) {
+  const likes = []
+  return {
+    posts,
+    likes,
+    addLike: (l) => likes.push(l)
+  }
+}
+
+// Decode a like payload back into a 64-character hex txid.
+function decodeLikeTxid (raw) {
+  return Buffer.from(raw).toString('hex')
+}
+
+test('MEMO_LIKE_PREFIX is the Memo like action 0x6d04', () => {
+  assert.equal(MemoLike.MEMO_LIKE_PREFIX, '6d04')
+})
+
+test('DUST_LIMIT_SATS is 3000', () => {
+  assert.equal(MemoLike.DUST_LIMIT_SATS, 3000)
+})
+
+test('MAX_TIP_SATS is 100000000', () => {
+  assert.equal(MemoLike.MAX_TIP_SATS, 100000000)
+})
+
+test('liking a post without a tip broadcasts an OP_RETURN with the Memo like prefix and txid', async () => {
+  const wallet = fakeWallet({ cashAddress: MY_ADDRESS })
+  const feed = fakeFeed([{ txid: POST_TXID, addr: AUTHOR_ADDRESS, likeCount: 0 }])
+  const memoLike = new MemoLike({ wallet, feed })
+
+  const txid = await memoLike.like(POST_TXID, 0, AUTHOR_ADDRESS)
+
+  assert.equal(txid, 'fake-txid')
+  assert.equal(wallet.broadcasts.length, 1)
+  const b = wallet.broadcasts[0]
+  assert.equal(b.prefix, '6d04')
+  assert.ok(b.msg instanceof Uint8Array)
+  assert.equal(decodeLikeTxid(b.msg), POST_TXID)
+  assert.deepEqual(b.bchOutput, [])
+
+  // The feed reflects the like.
+  assert.equal(feed.likes.length, 1)
+  assert.equal(feed.likes[0].postTxid, POST_TXID)
+  assert.equal(feed.likes[0].address, MY_ADDRESS)
+  assert.equal(feed.likes[0].tipSats, 0)
+  assert.equal(feed.posts[0].likeCount, 1)
+})
+
+test('liking a post with a tip broadcasts an OP_RETURN and a tip output', async () => {
+  const wallet = fakeWallet({ cashAddress: MY_ADDRESS, utxos: [{ txid: 'u1', value: 100000 }] })
+  const feed = fakeFeed([{ txid: POST_TXID, addr: AUTHOR_ADDRESS, likeCount: 5 }])
+  const memoLike = new MemoLike({ wallet, feed })
+
+  const txid = await memoLike.like(POST_TXID, 3000, AUTHOR_ADDRESS)
+
+  assert.equal(txid, 'fake-txid')
+  assert.equal(wallet.broadcasts.length, 1)
+  const b = wallet.broadcasts[0]
+  assert.equal(b.prefix, '6d04')
+  assert.equal(decodeLikeTxid(b.msg), POST_TXID)
+  assert.deepEqual(b.bchOutput, [{ address: AUTHOR_ADDRESS, amountSat: 3000 }])
+
+  // The feed reflects the like.
+  assert.equal(feed.likes.length, 1)
+  assert.equal(feed.likes[0].tipSats, 3000)
+  assert.equal(feed.posts[0].likeCount, 6)
+})
+
+test('liking without a wallet reports a missing-wallet error', async () => {
+  const memoLike = new MemoLike({})
+
+  await assert.rejects(
+    memoLike.like(POST_TXID),
+    (err) => /wallet/i.test(err.message)
+  )
+})
+
+test('liking with an invalid post txid reports a clear validation error', async () => {
+  const wallet = fakeWallet()
+  const memoLike = new MemoLike({ wallet })
+
+  await assert.rejects(
+    memoLike.like('not-a-txid'),
+    (err) => err.code === 'like_validation'
+  )
+  assert.equal(wallet.broadcasts.length, 0)
+})
+
+test('liking with a wrong-length but valid-hex post txid is rejected', async () => {
+  const wallet = fakeWallet()
+  const memoLike = new MemoLike({ wallet })
+
+  await assert.rejects(
+    memoLike.like('a'.repeat(10)),
+    (err) => err.code === 'like_validation'
+  )
+  assert.equal(wallet.broadcasts.length, 0)
+})
+
+test('a non-integer tip like "1.5" is rejected with a validation error', async () => {
+  const wallet = fakeWallet()
+  const memoLike = new MemoLike({ wallet })
+
+  await assert.rejects(
+    memoLike.like(POST_TXID, 1.5, AUTHOR_ADDRESS),
+    (err) => err.code === 'like_validation'
+  )
+  assert.equal(wallet.broadcasts.length, 0)
+})
+
+test('a non-numeric tip like "abc" is rejected with a validation error', async () => {
+  const wallet = fakeWallet()
+  const memoLike = new MemoLike({ wallet })
+
+  await assert.rejects(
+    memoLike.like(POST_TXID, NaN, AUTHOR_ADDRESS),
+    (err) => err.code === 'like_validation'
+  )
+  assert.equal(wallet.broadcasts.length, 0)
+})
+
+test('a negative tip is rejected with a validation error', async () => {
+  const wallet = fakeWallet()
+  const memoLike = new MemoLike({ wallet })
+
+  await assert.rejects(
+    memoLike.like(POST_TXID, -1, AUTHOR_ADDRESS),
+    (err) => err.code === 'like_validation'
+  )
+  assert.equal(wallet.broadcasts.length, 0)
+})
+
+test('a tip below the dust limit is rejected with a dust error', async () => {
+  const wallet = fakeWallet({ utxos: [{ txid: 'u1', value: 100000 }] })
+  const memoLike = new MemoLike({ wallet })
+
+  for (const tip of [1, 2999]) {
+    await assert.rejects(
+      memoLike.like(POST_TXID, tip, AUTHOR_ADDRESS),
+      (err) => err.code === 'like_dust'
+    )
+  }
+  assert.equal(wallet.broadcasts.length, 0)
+})
+
+test('a tip at the dust limit is accepted', async () => {
+  const wallet = fakeWallet({ utxos: [{ txid: 'u1', value: 100000 }] })
+  const memoLike = new MemoLike({ wallet })
+
+  const txid = await memoLike.like(POST_TXID, 3000, AUTHOR_ADDRESS)
+
+  assert.equal(txid, 'fake-txid')
+  assert.equal(wallet.broadcasts.length, 1)
+})
+
+test('a tip above the hard maximum is rejected with a maximum error', async () => {
+  const wallet = fakeWallet({ utxos: [{ txid: 'u1', value: 150000000 }] })
+  const memoLike = new MemoLike({ wallet })
+
+  await assert.rejects(
+    memoLike.like(POST_TXID, 100000001, AUTHOR_ADDRESS),
+    (err) => err.code === 'like_maximum'
+  )
+  assert.equal(wallet.broadcasts.length, 0)
+})
+
+test('a tip above the spendable balance is rejected with a balance error', async () => {
+  const wallet = fakeWallet({ utxos: [{ txid: 'u1', value: 30000 }] })
+  const memoLike = new MemoLike({ wallet })
+
+  await assert.rejects(
+    memoLike.like(POST_TXID, 35000, AUTHOR_ADDRESS),
+    (err) => err.code === 'like_balance'
+  )
+  assert.equal(wallet.broadcasts.length, 0)
+})
+
+test('a wallet with zero spendable balance cannot like', async () => {
+  const wallet = fakeWallet({ utxos: [] })
+  const memoLike = new MemoLike({ wallet })
+
+  await assert.rejects(
+    memoLike.like(POST_TXID, 0, AUTHOR_ADDRESS),
+    (err) => err.code === 'like_empty_balance'
+  )
+  assert.equal(wallet.broadcasts.length, 0)
+})
+
+test('a wallet with balance below the dust limit cannot like', async () => {
+  const wallet = fakeWallet({ utxos: [{ txid: 'u1', value: 2999 }] })
+  const memoLike = new MemoLike({ wallet })
+
+  await assert.rejects(
+    memoLike.like(POST_TXID, 0, AUTHOR_ADDRESS),
+    (err) => err.code === 'like_empty_balance'
+  )
+  assert.equal(wallet.broadcasts.length, 0)
+})
+
+test('a pure like can be made on a post authored by the wallet address', async () => {
+  const wallet = fakeWallet({ cashAddress: MY_ADDRESS })
+  const feed = fakeFeed([{ txid: POST_TXID, addr: MY_ADDRESS, likeCount: 0 }])
+  const memoLike = new MemoLike({ wallet, feed })
+
+  const txid = await memoLike.like(POST_TXID, 0, MY_ADDRESS)
+
+  assert.equal(txid, 'fake-txid')
+  assert.equal(wallet.broadcasts.length, 1)
+  assert.equal(wallet.broadcasts[0].prefix, '6d04')
+  assert.equal(feed.posts[0].likeCount, 1)
+})
+
+test('a tip requires an author address', async () => {
+  const wallet = fakeWallet({ utxos: [{ txid: 'u1', value: 100000 }] })
+  const memoLike = new MemoLike({ wallet })
+
+  await assert.rejects(
+    memoLike.like(POST_TXID, 3000),
+    (err) => err.code === 'like_validation'
+  )
+  assert.equal(wallet.broadcasts.length, 0)
+})
+
+test('getSpendableSats tolerates common utxo value field names', () => {
+  const walletValue = fakeWallet({ utxos: [{ txid: 'u1', value: 1000 }] })
+  const walletSatoshis = fakeWallet({ utxos: [{ txid: 'u2', satoshis: 2000 }] })
+  const walletAmount = fakeWallet({ utxos: [{ txid: 'u3', amount: 3000 }] })
+
+  assert.equal(new MemoLike({ wallet: walletValue }).getSpendableSats(), 1000)
+  assert.equal(new MemoLike({ wallet: walletSatoshis }).getSpendableSats(), 2000)
+  assert.equal(new MemoLike({ wallet: walletAmount }).getSpendableSats(), 3000)
+})