From 8b2babfa5db487391e9ed89d5ee8b25fce080a85 Mon Sep 17 00:00:00 2001
From: Mplan <mplan_@outlook.com>
Date: Tue, 16 Jun 2026 02:01:02 +0800
Subject: [PATCH] feat: add explain, review, changelog, and suggest commands

- gai explain: plain-language diff explanation with pipe support
- gai review: AI code review with strict/normal/lenient modes
- gai changelog: generate user-facing changelog from commits,
  supports --from/--to ranges and -n count
- gai suggest: suggest branch names or commit type from diff
- All commands support pipe input and auto-stage on empty staging area
---
 src/commands/changelog.ts |  81 +++++++++++++++++++++
 src/commands/explain.ts   | 129 +++++++++++++++++++++++++++++++++
 src/commands/review.ts    | 129 +++++++++++++++++++++++++++++++++
 src/commands/suggest.ts   | 146 ++++++++++++++++++++++++++++++++++++++
 4 files changed, 485 insertions(+)
 create mode 100644 src/commands/changelog.ts
 create mode 100644 src/commands/explain.ts
 create mode 100644 src/commands/review.ts
 create mode 100644 src/commands/suggest.ts

diff --git a/src/commands/changelog.ts b/src/commands/changelog.ts
new file mode 100644
index 0000000..4d3b723
--- /dev/null
+++ b/src/commands/changelog.ts
@@ -0,0 +1,81 @@
+import { loadConfig } from "../config";
+import { isGitRepo, getRecentCommits } from "../git";
+import { CHANGELOG_SYSTEM_PROMPT, buildChangelogPrompt } from "../prompt";
+import { callAI } from "../ai";
+import { BOLD, RED, DIM, RESET, CYAN } from "../terminal";
+import { isStdinTTY } from "../tty";
+import type { StreamCallbacks } from "../types";
+import type { ParsedArgs } from "../cli";
+
+export async function handleChangelog(args: ParsedArgs): Promise<number> {
+  const config = await loadConfig();
+
+  if (!config.apiKey) {
+    console.error(`\n  ${RED()}Error: API key not set. Run ${BOLD()}gai config${RESET()}${RED()} to configure.${RESET()}\n`);
+    return 1;
+  }
+
+  if (!(await isGitRepo())) {
+    console.error(`\n  ${RED()}Error: Not a git repository.${RESET()}\n`);
+    return 1;
+  }
+
+  const from = args.flags["from"] as string | undefined;
+  const to = args.flags["to"] as string | undefined;
+  const countFlag = args.flags["count"] as number | undefined;
+  const verbose = args.flags["verbose"] as boolean;
+
+  // Collect commits
+  let commits: string[];
+
+  if (from) {
+    // Range-based: get commits between from..to
+    const range = to ? `${from}..${to}` : `${from}..HEAD`;
+    try {
+      const result = await Bun.$`git log --oneline ${range}`.quiet().text();
+      commits = result.trim().split("\n").filter(Boolean);
+    } catch {
+      console.error(`\n  ${RED()}Error: Invalid range: ${range}${RESET()}\n`);
+      return 1;
+    }
+  } else {
+    // Count-based
+    const count = typeof countFlag === "number" ? countFlag : 20;
+    commits = await getRecentCommits(count);
+  }
+
+  if (commits.length === 0) {
+    console.log(`  ${DIM()}No commits found for the specified range.${RESET()}`);
+    return 0;
+  }
+
+  if (verbose) {
+    console.log(`  ${DIM()}Processing ${commits.length} commits${RESET()}`);
+    console.log(`  ${DIM()}Model: ${config.model} | API: ${config.apiBase}${RESET()}`);
+  }
+
+  const userPrompt = buildChangelogPrompt(commits, from, to);
+
+  const tty = isStdinTTY();
+  if (tty) {
+    console.log(`\n  ${BOLD()}${CYAN()}Generating changelog from ${commits.length} commits...${RESET()}\n`);
+  }
+
+  try {
+    const callbacks: StreamCallbacks = tty ? {
+      onToken: (token) => process.stdout.write(token),
+    } : undefined;
+
+    const result = await callAI(config, CHANGELOG_SYSTEM_PROMPT, userPrompt, callbacks);
+    if (callbacks) {
+      process.stdout.write("\n");
+    } else {
+      process.stdout.write(result + "\n");
+    }
+  } catch (err) {
+    console.error(`\n  ${RED()}AI request failed: ${err instanceof Error ? err.message : err}${RESET()}\n`);
+    return 1;
+  }
+
+  return 0;
+}
diff --git a/src/commands/explain.ts b/src/commands/explain.ts
new file mode 100644
index 0000000..3ab11b2
--- /dev/null
+++ b/src/commands/explain.ts
@@ -0,0 +1,129 @@
+import { loadConfig } from "../config";
+import { isGitRepo, getStagedDiff, getUnstagedFiles, getRepoRoot, stageFiles } from "../git";
+import { selectFiles } from "../selector";
+import { BACK } from "../menu";
+import { collectProjectContext } from "../context";
+import { EXPLAIN_SYSTEM_PROMPT, buildExplainPrompt } from "../prompt";
+import { callAI } from "../ai";
+import { BOLD, GREEN, RED, DIM, RESET, CYAN } from "../terminal";
+import { isStdinTTY } from "../tty";
+import type { StreamCallbacks } from "../types";
+import type { ParsedArgs } from "../cli";
+
+export async function handleExplain(args: ParsedArgs): Promise<number> {
+  const config = await loadConfig();
+
+  if (!config.apiKey) {
+    console.error(`\n  ${RED()}Error: API key not set. Run ${BOLD()}gai config${RESET()}${RED()} to configure.${RESET()}\n`);
+    return 1;
+  }
+
+  const unstaged = args.flags["unstaged"] as boolean;
+  const staged = args.flags["staged"] as boolean;
+  const verbose = args.flags["verbose"] as boolean;
+
+  // Determine which diff to explain
+  let diff: string;
+  let sourceLabel: string;
+
+  if (unstaged) {
+    if (!(await isGitRepo())) {
+      console.error(`\n  ${RED()}Error: Not a git repository.${RESET()}\n`);
+      return 1;
+    }
+    try {
+      diff = (await Bun.$`git diff`.quiet().text()).trim();
+    } catch {
+      diff = "";
+    }
+    sourceLabel = "unstaged changes";
+  } else {
+    // Default: staged changes (or piped)
+    if (isStdinTTY()) {
+      if (!(await isGitRepo())) {
+        console.error(`\n  ${RED()}Error: Not a git repository.${RESET()}\n`);
+        return 1;
+      }
+      diff = await getStagedDiff();
+      sourceLabel = "staged changes";
+
+      // If no staged changes, offer to stage unstaged files
+      if (!diff) {
+        const unstagedFiles = await getUnstagedFiles();
+        if (unstagedFiles.length > 0) {
+          const selected = await selectFiles([], unstagedFiles);
+          if (selected === BACK) return 0;
+          if (selected.length > 0) {
+            await stageFiles(selected);
+            console.log(`  ${GREEN()}Staged ${selected.length} file(s).${RESET()}`);
+            diff = await getStagedDiff();
+          }
+        }
+      }
+    } else {
+      // Read from pipe
+      const chunks: Buffer[] = [];
+      for await (const chunk of process.stdin) {
+        chunks.push(typeof chunk === "string" ? Buffer.from(chunk) : chunk);
+      }
+      diff = Buffer.concat(chunks).toString("utf-8").trim();
+      sourceLabel = "piped input";
+    }
+  }
+
+  if (!diff) {
+    console.log(`  ${DIM()}No ${sourceLabel} to explain.${RESET()}`);
+    return 0;
+  }
+
+  if (args.flags["verbose"]) {
+    console.log(`  ${DIM()}Explaining ${sourceLabel} (${diff.length} bytes)${RESET()}`);
+  }
+
+  const MAX_DIFF_SIZE = 15000;
+  const truncatedDiff = diff.length > MAX_DIFF_SIZE
+    ? diff.substring(0, MAX_DIFF_SIZE) + "\n... (truncated)"
+    : diff;
+
+  // Collect project context for better explanations
+  let contextPrefix = "";
+  try {
+    if (await isGitRepo()) {
+      const repoRoot = await getRepoRoot();
+      const ctx = await collectProjectContext(repoRoot);
+      if (ctx.packageDescription) {
+        contextPrefix = `Project: ${ctx.packageDescription}\n\n`;
+      }
+    }
+  } catch {}
+
+  const userPrompt = contextPrefix + buildExplainPrompt(truncatedDiff);
+
+  if (verbose) {
+    console.log(`  ${DIM()}Model: ${config.model} | API: ${config.apiBase}${RESET()}`);
+  }
+
+  const tty = isStdinTTY();
+  if (tty) {
+    console.log(`\n  ${BOLD()}${CYAN()}Analyzing ${sourceLabel}...${RESET()}\n`);
+  }
+
+  try {
+    const callbacks: StreamCallbacks = tty ? {
+      onToken: (token) => process.stdout.write(token),
+    } : undefined;
+
+    const explanation = await callAI(config, EXPLAIN_SYSTEM_PROMPT, userPrompt, callbacks);
+    if (callbacks) {
+      process.stdout.write("\n");
+    } else {
+      // Non-TTY: print the result directly
+      process.stdout.write(explanation + "\n");
+    }
+  } catch (err) {
+    console.error(`\n  ${RED()}AI request failed: ${err instanceof Error ? err.message : err}${RESET()}\n`);
+    return 1;
+  }
+
+  return 0;
+}
diff --git a/src/commands/review.ts b/src/commands/review.ts
new file mode 100644
index 0000000..4664dc8
--- /dev/null
+++ b/src/commands/review.ts
@@ -0,0 +1,129 @@
+import { loadConfig } from "../config";
+import { isGitRepo, getStagedDiff, getUnstagedFiles, getRepoRoot, stageFiles } from "../git";
+import { selectFiles } from "../selector";
+import { BACK } from "../menu";
+import { collectProjectContext } from "../context";
+import { REVIEW_SYSTEM_PROMPT, buildReviewPrompt } from "../prompt";
+import { callAI } from "../ai";
+import { BOLD, GREEN, YELLOW, RED, DIM, RESET, CYAN } from "../terminal";
+import { isStdinTTY } from "../tty";
+import type { StreamCallbacks } from "../types";
+import type { ParsedArgs } from "../cli";
+
+export async function handleReview(args: ParsedArgs): Promise<number> {
+  const config = await loadConfig();
+
+  if (!config.apiKey) {
+    console.error(`\n  ${RED()}Error: API key not set. Run ${BOLD()}gai config${RESET()}${RED()} to configure.${RESET()}\n`);
+    return 1;
+  }
+
+  const strictnessFlag = args.flags["strict"] as boolean
+    ? "strict"
+    : args.flags["lenient"] as boolean
+      ? "lenient"
+      : "normal";
+
+  const unstaged = args.flags["unstaged"] as boolean;
+  const verbose = args.flags["verbose"] as boolean;
+
+  let diff: string;
+  let sourceLabel: string;
+
+  if (unstaged) {
+    if (!(await isGitRepo())) {
+      console.error(`\n  ${RED()}Error: Not a git repository.${RESET()}\n`);
+      return 1;
+    }
+    try {
+      diff = (await Bun.$`git diff`.quiet().text()).trim();
+    } catch {
+      diff = "";
+    }
+    sourceLabel = "unstaged changes";
+  } else if (!isStdinTTY()) {
+    const chunks: Buffer[] = [];
+    for await (const chunk of process.stdin) {
+      chunks.push(typeof chunk === "string" ? Buffer.from(chunk) : chunk);
+    }
+    diff = Buffer.concat(chunks).toString("utf-8").trim();
+    sourceLabel = "piped input";
+  } else {
+    if (!(await isGitRepo())) {
+      console.error(`\n  ${RED()}Error: Not a git repository.${RESET()}\n`);
+      return 1;
+    }
+    diff = await getStagedDiff();
+    sourceLabel = "staged changes";
+
+    // If no staged changes, offer to stage unstaged files
+    if (!diff) {
+      const unstagedFiles = await getUnstagedFiles();
+      if (unstagedFiles.length > 0) {
+        const selected = await selectFiles([], unstagedFiles);
+        if (selected === BACK) return 0;
+        if (selected.length > 0) {
+          await stageFiles(selected);
+          console.log(`  ${GREEN()}Staged ${selected.length} file(s).${RESET()}`);
+          diff = await getStagedDiff();
+        }
+      }
+    }
+  }
+
+  if (!diff) {
+    console.log(`  ${DIM()}No ${sourceLabel} to review.${RESET()}`);
+    return 0;
+  }
+
+  const MAX_DIFF_SIZE = 15000;
+  const truncatedDiff = diff.length > MAX_DIFF_SIZE
+    ? diff.substring(0, MAX_DIFF_SIZE) + "\n... (truncated)"
+    : diff;
+
+  let contextPrefix = "";
+  try {
+    if (await isGitRepo()) {
+      const repoRoot = await getRepoRoot();
+      const ctx = await collectProjectContext(repoRoot);
+      if (ctx.packageDescription) {
+        contextPrefix = `Project: ${ctx.packageDescription}\n\n`;
+      }
+    }
+  } catch {}
+
+  const userPrompt = contextPrefix + buildReviewPrompt(truncatedDiff, strictnessFlag);
+
+  const strictnessLabel = strictnessFlag === "strict"
+    ? `${RED()}strict${RESET()}`
+    : strictnessFlag === "lenient"
+      ? `${GREEN()}lenient${RESET()}`
+      : `${YELLOW()}normal${RESET()}`;
+
+  if (verbose) {
+    console.log(`  ${DIM()}Model: ${config.model} | API: ${config.apiBase} | Strictness: ${strictnessFlag}${RESET()}`);
+  }
+
+  const tty = isStdinTTY();
+  if (tty) {
+    console.log(`\n  ${BOLD()}${CYAN()}Reviewing ${sourceLabel} (${strictnessLabel})...${RESET()}\n`);
+  }
+
+  try {
+    const callbacks: StreamCallbacks = tty ? {
+      onToken: (token) => process.stdout.write(token),
+    } : undefined;
+
+    const result = await callAI(config, REVIEW_SYSTEM_PROMPT, userPrompt, callbacks);
+    if (callbacks) {
+      process.stdout.write("\n");
+    } else {
+      process.stdout.write(result + "\n");
+    }
+  } catch (err) {
+    console.error(`\n  ${RED()}AI request failed: ${err instanceof Error ? err.message : err}${RESET()}\n`);
+    return 1;
+  }
+
+  return 0;
+}
diff --git a/src/commands/suggest.ts b/src/commands/suggest.ts
new file mode 100644
index 0000000..970e88a
--- /dev/null
+++ b/src/commands/suggest.ts
@@ -0,0 +1,146 @@
+import { loadConfig } from "../config";
+import { isGitRepo, getStagedDiff, getUnstagedFiles, stageFiles } from "../git";
+import { selectFiles } from "../selector";
+import { BACK } from "../menu";
+import {
+  SUGGEST_SYSTEM_PROMPT,
+  buildSuggestBranchPrompt,
+  buildSuggestTypePrompt,
+} from "../prompt";
+import { callAI } from "../ai";
+import { BOLD, GREEN, YELLOW, RED, DIM, RESET, CYAN } from "../terminal";
+import { isStdinTTY } from "../tty";
+import type { Config } from "../types";
+import type { ParsedArgs } from "../cli";
+
+export async function handleSuggest(args: ParsedArgs): Promise<number> {
+  const config = await loadConfig();
+
+  if (!config.apiKey) {
+    console.error(`\n  ${RED()}Error: API key not set. Run ${BOLD()}gai config${RESET()}${RED()} to configure.${RESET()}\n`);
+    return 1;
+  }
+
+  const mode = args.positional[0] || "branch";
+  const verbose = args.flags["verbose"] as boolean;
+
+  if (mode !== "branch" && mode !== "type") {
+    console.error(`\n  ${RED()}Error: Unknown suggest mode: ${mode}${RESET()}`);
+    console.error(`  Try: gai suggest branch | gai suggest type\n`);
+    return 1;
+  }
+
+  // Get diff (staged, or unstaged if --unstaged, or piped)
+  let diff: string;
+  if (!isStdinTTY()) {
+    const chunks: Buffer[] = [];
+    for await (const chunk of process.stdin) {
+      chunks.push(typeof chunk === "string" ? Buffer.from(chunk) : chunk);
+    }
+    diff = Buffer.concat(chunks).toString("utf-8").trim();
+  } else {
+    if (!(await isGitRepo())) {
+      console.error(`\n  ${RED()}Error: Not a git repository.${RESET()}\n`);
+      return 1;
+    }
+
+    if (args.flags["unstaged"] as boolean) {
+      try {
+        diff = (await Bun.$`git diff`.quiet().text()).trim();
+      } catch {
+        diff = "";
+      }
+    } else {
+      diff = await getStagedDiff();
+
+      // If no staged changes, offer to stage unstaged files
+      if (!diff) {
+        const unstagedFiles = await getUnstagedFiles();
+        if (unstagedFiles.length > 0) {
+          const selected = await selectFiles([], unstagedFiles);
+          if (selected === BACK) return 0;
+          if (selected.length > 0) {
+            await stageFiles(selected);
+            console.log(`  ${GREEN()}Staged ${selected.length} file(s).${RESET()}`);
+            diff = await getStagedDiff();
+          }
+        }
+      }
+    }
+  }
+
+  if (!diff) {
+    console.log(`  ${DIM()}No changes to suggest from.${RESET()}`);
+    return 0;
+  }
+
+  const MAX_DIFF_SIZE = 15000;
+  const truncatedDiff = diff.length > MAX_DIFF_SIZE
+    ? diff.substring(0, MAX_DIFF_SIZE) + "\n... (truncated)"
+    : diff;
+
+  if (verbose) {
+    console.log(`  ${DIM()}Model: ${config.model} | API: ${config.apiBase}${RESET()}`);
+  }
+
+  if (mode === "branch") {
+    return handleSuggestBranch(config, truncatedDiff);
+  } else {
+    return handleSuggestType(config, truncatedDiff);
+  }
+}
+
+async function handleSuggestBranch(config: Config, diff: string): Promise<number> {
+  const tty = isStdinTTY();
+  if (tty) {
+    console.log(`\n  ${BOLD()}${CYAN()}Suggesting branch names...${RESET()}\n`);
+  }
+
+  try {
+    const raw = await callAI(config, SUGGEST_SYSTEM_PROMPT, buildSuggestBranchPrompt(diff));
+    const suggestions = raw
+      .split("\n")
+      .map((line) => line.replace(/^[\d.\s\-*]+/, "").trim())
+      .filter(Boolean);
+
+    if (suggestions.length === 0) {
+      console.log(`  ${DIM()}No suggestions generated.${RESET()}`);
+      return 0;
+    }
+
+    for (const s of suggestions) {
+      console.log(`    ${GREEN()}${s}${RESET()}`);
+    }
+    console.log("");
+  } catch (err) {
+    console.error(`\n  ${RED()}AI request failed: ${err instanceof Error ? err.message : err}${RESET()}\n`);
+    return 1;
+  }
+
+  return 0;
+}
+
+async function handleSuggestType(config: Config, diff: string): Promise<number> {
+  const tty = isStdinTTY();
+  if (tty) {
+    console.log(`\n  ${BOLD()}${CYAN()}Suggesting commit type...${RESET()}\n`);
+  }
+
+  try {
+    const raw = await callAI(config, SUGGEST_SYSTEM_PROMPT, buildSuggestTypePrompt(diff));
+    const type = raw.trim().toLowerCase();
+    const validTypes = ["feat", "fix", "docs", "style", "refactor", "perf", "test", "build", "ci", "chore", "revert"];
+
+    if (validTypes.includes(type)) {
+      console.log(`    Suggested type: ${GREEN()}${BOLD()}${type}${RESET()}\n`);
+    } else {
+      console.log(`    Suggested type: ${YELLOW()}${raw.trim()}${RESET()}`);
+      console.log(`    ${DIM()}(Not a standard Conventional Commit type)${RESET()}\n`);
+    }
+  } catch (err) {
+    console.error(`\n  ${RED()}AI request failed: ${err instanceof Error ? err.message : err}${RESET()}\n`);
+    return 1;
+  }
+
+  return 0;
+}