/**
 * @file The dev-based-flow safety primitive: the ONE sanctioned merge in the
 * ship-feature-lane pipeline, origin/development INTO a lane's feature
 * branch, gated by a migration-number collision preflight. Port of
 * Shipyard's lane-sync-dev.sh. Pure git — every operation goes through
 * worktree.js's git() execFile wrapper, never a shell string.
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */

const fs = require("node:fs");
const path = require("node:path");
const { git } = require("./worktree");
const { runHook } = require("./lane-profile");

/** The PR base branch. Hardcoded — the whole ship-feature-lane pipeline
 *  already hardcodes this name throughout SKILL.md; a configurable version
 *  would be scope this task doesn't need. */
const INTEGRATION_BRANCH = "development";

function badBranch(message) {
  return Object.assign(new Error(message), { code: "EBADBRANCH" });
}

/** The branch to operate on: the caller's explicit choice, or the lane's
 *  current HEAD when omitted (mirrors the source script's own fallback). */
async function resolveBranch(cwd, branch) {
  if (branch) return branch;
  const result = await git(cwd, ["rev-parse", "--abbrev-ref", "HEAD"]);
  return result.stdout.trim();
}

function assertFeatureBranch(branch) {
  if (branch === INTEGRATION_BRANCH || branch === "main") {
    throw badBranch(
      `branch is '${branch}' — sync-base works on a feature branch (pass it explicitly)`
    );
  }
}

async function assertBranchExists(cwd, branch) {
  try {
    await git(cwd, ["rev-parse", "--verify", "--quiet", branch]);
  } catch {
    throw badBranch(`feature branch '${branch}' not found`);
  }
}

/**
 * Migration-number collision guard: two lanes independently add NNN_* files
 * with the same number under MIGRATIONS_DIR — git merges both without
 * conflict, and the collision only surfaces as red CI on development AFTER a
 * human merges the PR. Detected from refs alone, before anything is merged.
 */
async function collisionCheck(cwd, migrationsDir, branch) {
  if (!migrationsDir) return [];

  const addedResult = await git(cwd, [
    "diff",
    "--name-only",
    "--diff-filter=A",
    `origin/${INTEGRATION_BRANCH}...${branch}`,
    "--",
    migrationsDir,
  ]);
  const added = addedResult.stdout
    .split("\n")
    .map((line) => line.trim())
    .filter(Boolean);
  if (!added.length) return [];

  const treeResult = await git(cwd, [
    "ls-tree",
    "-r",
    "--name-only",
    `origin/${INTEGRATION_BRANCH}`,
    "--",
    migrationsDir,
  ]);
  const devMigrations = treeResult.stdout
    .split("\n")
    .map((line) => line.trim())
    .filter((line) => /\/\d+_[^/]+$/.test(line));

  let maxNum = 0;
  for (const file of devMigrations) {
    const m = /\/(\d+)_[^/]+$/.exec(file);
    if (m) maxNum = Math.max(maxNum, parseInt(m[1], 10));
  }
  let nextNum = maxNum + 1;

  const collisions = [];
  for (const file of added) {
    const base = path.basename(file);
    const m = /^(\d+)_/.exec(base);
    if (!m) continue;
    const num = m[1];
    const clash = devMigrations.find((f) => f.includes(`/${num}_`));
    if (!clash) continue;
    const suggestion = `${String(nextNum).padStart(3, "0")}_${base.replace(/^\d+_/, "")}`;
    collisions.push({ file, collidesWith: clash, suggestion });
    nextNum += 1;
  }
  return collisions;
}

/** What moved on origin/development since branch's merge-base, and whether
 *  that delta touches branch's own changed files. Informational. */
async function devDeltaReport(cwd, branch, generatedPaths) {
  let mergeBase = "";
  try {
    const result = await git(cwd, ["merge-base", `origin/${INTEGRATION_BRANCH}`, branch]);
    mergeBase = result.stdout.trim();
  } catch {
    mergeBase = "";
  }
  if (!mergeBase) return { devDelta: null, overlap: null };

  const filterGenerated = (files) =>
    generatedPaths.length ? files.filter((f) => !generatedPaths.includes(f)) : files;
  const namesOnly = (stdout) =>
    stdout
      .split("\n")
      .map((line) => line.trim())
      .filter(Boolean);

  const devDiff = await git(cwd, [
    "diff",
    "--name-only",
    mergeBase,
    `origin/${INTEGRATION_BRANCH}`,
  ]);
  const delta = filterGenerated(namesOnly(devDiff.stdout));

  const featDiff = await git(cwd, ["diff", "--name-only", mergeBase, branch]);
  const featFiles = new Set(filterGenerated(namesOnly(featDiff.stdout)));

  const overlap = delta.filter((f) => featFiles.has(f));
  return { devDelta: delta, overlap };
}

/** Read-only preflight: fetch + collision check + dev-delta report. Merges
 *  nothing. */
async function checkSync(lane, profile, branchArg) {
  const branch = await resolveBranch(lane.cwd, branchArg);
  assertFeatureBranch(branch);
  await assertBranchExists(lane.cwd, branch);
  await git(lane.cwd, ["fetch", "origin", "--prune"]);

  const collisions = await collisionCheck(lane.cwd, profile.env.MIGRATIONS_DIR, branch);
  if (collisions.length) return { code: 5, collisions };

  const { devDelta, overlap } = await devDeltaReport(lane.cwd, branch, profile.generatedMergePaths);
  return { code: 0, devDelta, overlap };
}

/** The worktree-private git dir (HEAD, index, MERGE_HEAD live here — distinct
 *  from the shared common dir below). Resolved fresh each call: cheap, and a
 *  cached value would go stale the moment a lane's slot/worktree changes. */
async function gitDir(cwd) {
  const result = await git(cwd, ["rev-parse", "--git-dir"]);
  const dir = result.stdout.trim();
  return path.isAbsolute(dir) ? dir : path.join(cwd, dir);
}

/** The dir shared across every worktree of a repo — where info/attributes
 *  and git config live. For a plain (non-worktree) clone this is the same
 *  as gitDir(); for a `git worktree add` lane it is the source repo's own
 *  .git, so the merge driver is configured once per repository, not once
 *  per lane. */
async function commonGitDir(cwd) {
  const result = await git(cwd, ["rev-parse", "--git-common-dir"]);
  const dir = result.stdout.trim();
  return path.isAbsolute(dir) ? dir : path.join(cwd, dir);
}

async function unmergedFiles(cwd) {
  const result = await git(cwd, ["ls-files", "-u"]);
  const files = new Set();
  for (const line of result.stdout.split("\n")) {
    const tab = line.indexOf("\t");
    if (tab > -1) files.add(line.slice(tab + 1));
  }
  return [...files];
}

/** Generated artifacts (an OpenAPI contract, its generated client, ...) must
 *  never be hand-merged: a keep-ours driver (`true` exits 0 -> keep our
 *  side, no conflict) via the clone-local attributes file, idempotent every
 *  call — same "idempotent, never automatic" shape this repo's proof-link
 *  already established. */
async function setupMergeDriver(cwd, generatedPaths) {
  if (!generatedPaths.length) return;
  await git(cwd, ["config", "merge.ccam-generated.driver", "true"]);
  await git(cwd, [
    "config",
    "merge.ccam-generated.name",
    "keep ours; regenerated post-merge by the profile regen hook",
  ]);

  const infoDir = path.join(await commonGitDir(cwd), "info");
  fs.mkdirSync(infoDir, { recursive: true });
  const attrPath = path.join(infoDir, "attributes");
  const existing = fs.existsSync(attrPath) ? fs.readFileSync(attrPath, "utf8") : "";
  const lines = new Set(existing.split("\n").filter(Boolean));
  let changed = false;
  for (const gp of generatedPaths) {
    const line = `${gp} merge=ccam-generated`;
    if (!lines.has(line)) {
      lines.add(line);
      changed = true;
    }
  }
  if (changed) fs.writeFileSync(attrPath, [...lines].join("\n") + "\n");
}

/** Regenerate generated artifacts from the just-synced tree and fold them
 *  into the merge commit (or, on the --continue path, a follow-up commit).
 *  A no-op when nothing changed. */
async function regenFold(lane, profile, generatedPaths) {
  if (!generatedPaths.length || !profile.hooks.has("regen")) return;
  await runHook(lane, profile, "regen", []);
  try {
    await git(lane.cwd, ["add", "--", ...generatedPaths]);
  } catch {
    // A generated path that doesn't exist yet on this branch is fine —
    // nothing to stage for it.
  }
  const staged = await git(lane.cwd, ["diff", "--cached", "--name-only"]);
  if (!staged.stdout.trim()) return;

  let isMergeCommit = true;
  try {
    await git(lane.cwd, ["rev-parse", "-q", "--verify", "HEAD^2"]);
  } catch {
    isMergeCommit = false;
  }
  if (isMergeCommit) {
    await git(lane.cwd, ["commit", "--amend", "--no-edit"]);
  } else {
    await git(lane.cwd, ["commit", "-m", "chore: regenerate artifacts after dev sync"]);
  }
}

/** The one sanctioned merge: origin/development INTO the feature branch. */
async function mergeSync(lane, profile, branchArg) {
  const branch = await resolveBranch(lane.cwd, branchArg);
  assertFeatureBranch(branch);
  await assertBranchExists(lane.cwd, branch);
  await git(lane.cwd, ["fetch", "origin", "--prune"]);

  const generatedPaths = profile.generatedMergePaths;
  await setupMergeDriver(lane.cwd, generatedPaths);

  const collisions = await collisionCheck(lane.cwd, profile.env.MIGRATIONS_DIR, branch);
  if (collisions.length) return { code: 5, collisions };

  await git(lane.cwd, ["checkout", "--quiet", branch]);

  try {
    await git(lane.cwd, ["merge", "--no-edit", `origin/${INTEGRATION_BRANCH}`]);
  } catch (err) {
    const mergeHeadPath = path.join(await gitDir(lane.cwd), "MERGE_HEAD");
    if (!fs.existsSync(mergeHeadPath)) throw err; // merge never started — a real git failure

    const conflicted = await unmergedFiles(lane.cwd);
    if (conflicted.length) {
      return { code: 4, conflictedFiles: conflicted };
    }
    // rerere auto-resolved every conflict but left the merge uncommitted — finish it.
    await git(lane.cwd, ["commit", "--no-edit"]);
  }

  await regenFold(lane, profile, generatedPaths);
  return { code: 0 };
}

/** Finish a sync after the session resolved a conflicted merge and
 *  committed it. Stateless — reads the lane's own git state directly rather
 *  than trusting a separate flag, so it can never disagree with reality. */
async function continueSync(lane, profile, branchArg) {
  const branch = await resolveBranch(lane.cwd, branchArg);

  const current = (await git(lane.cwd, ["rev-parse", "--abbrev-ref", "HEAD"])).stdout.trim();
  if (current !== branch) {
    throw badBranch(`--continue: lane is not on '${branch}' (currently on '${current}')`);
  }

  const unresolved = await unmergedFiles(lane.cwd);
  if (unresolved.length) {
    throw Object.assign(
      new Error(`--continue: unresolved conflicts remain: ${unresolved.join(", ")}`),
      { code: "EUNRESOLVED" }
    );
  }

  const mergeHeadPath = path.join(await gitDir(lane.cwd), "MERGE_HEAD");
  if (fs.existsSync(mergeHeadPath)) {
    throw Object.assign(new Error("--continue: merge not committed yet — git commit --no-edit"), {
      code: "EMERGEUNCOMMITTED",
    });
  }

  await regenFold(lane, profile, profile.generatedMergePaths);
  return { code: 0 };
}

module.exports = {
  INTEGRATION_BRANCH,
  checkSync,
  mergeSync,
  continueSync,
};