import { execFile as callback } from "node:child_process";
import { promisify } from "node:util";
import { realpath } from "node:fs/promises";
import path from "node:path";
import { parseQx, walkSyntax } from "./source.js";
import { authoringContext } from "./authoring-context.js";
import { readQxSource } from "./source-loader.js";
import { loadQuixosLock } from "../resource-lock/index.js";

const execFile = promisify(callback);
const git = async (root: string, args: string[]) =>
  (
    await execFile("git", ["-C", root, ...args], {
      maxBuffer: 8 * 1024 * 1024,
      env: { ...process.env, GIT_TERMINAL_PROMPT: "0" },
    })
  ).stdout;
const message = (error: unknown) => String(error instanceof Error ? error.message : error).slice(0, 2000);

/** Syntax-only contract inspection is deliberately NOT verification evidence.
 * Each file can recover independently; current valid files always win. */
export async function inspectAuthoringRepository(root: string, historyLimit = 100) {
  const names = (await git(root, ["ls-files", "-z", "--cached", "--others", "--exclude-standard"]))
    .split("\0")
    .filter((name) => name.endsWith(".qx"));
  if (names.length > 128)
    throw new Error("Repository inspection exceeds 128 QX files; split the resource into smaller repositories");
  const files = [];
  for (const name of [...new Set(names)].sort()) {
    let source = "",
      errors: unknown[] = [],
      revision: string | null = null;
    try {
      source = await readQxSource(root, name);
      if (source.length > 262144) throw new Error(`Inspection file exceeds 256 KiB: ${name}`);
      errors = parseQx(source, name).diagnostics;
    } catch (error) {
      errors = [{ message: message(error) }];
    }
    const currentErrors = errors;
    if (errors.length) {
      // Git can traverse jj's immutable commit DAG without mutating/snapshotting @.
      const head = await execFile("jj", ["--ignore-working-copy", "log", "--no-graph", "-r", "@", "-T", "commit_id"], {
        cwd: root,
        env: { ...process.env, QUIXOS_JJ_NO_CHECKPOINT: "1" },
      }).then(
        (r) => r.stdout.trim(),
        () => "HEAD",
      );
      const commits = await git(root, ["rev-list", `--max-count=${historyLimit}`, head, "--", name]).catch(() => "");
      for (const commit of commits.trim().split("\n").filter(Boolean)) {
        const historical = await git(root, ["show", `${commit}:${name}`]).catch(() => null);
        if (historical === null || historical.length > 262144) continue;
        if (!parseQx(historical, name).diagnostics.length) {
          source = historical;
          revision = commit;
          errors = [];
          break;
        }
      }
    }
    const syntax = errors.length ? null : parseQx(source, name);
    files.push({
      file: name,
      status: errors.length ? "unavailable" : revision ? "historical" : "current",
      revision,
      currentErrors: currentErrors.slice(0, 20),
      omittedErrors: Math.max(0, currentErrors.length - 20),
      declarations: syntax
        ? [...walkSyntax(syntax.root)]
            .filter((node) =>
              /^(?:interface|package|atom|state|edge|method|function|event|conformance)\w*Decl$/.test(node.kind),
            )
            .map((node) => ({ kind: node.kind, source: source.slice(node.start, node.end) }))
        : [],
    });
  }
  return { verificationEvidence: false as const, resolutionChecked: false as const, files };
}

export async function inspectWorkbench(start: string, selector?: string) {
  const context = await authoringContext(start);
  if (!selector || selector === ".") {
    const relative = path.relative(context.workbench, await realpath(start));
    selector =
      context.resources.find((entry) => relative === entry.directory || relative.startsWith(entry.directory + path.sep))
        ?.directory ?? "root";
  }
  const lock = await loadQuixosLock(path.join(context.workbench, "root/quixos.lock"));
  const aliases = lock.ok ? lock.lock.resources.filter((entry) => entry.binding === selector) : [];
  const selected = context.resources.filter(
    (entry) =>
      !selector ||
      selector === entry.directory ||
      selector === entry.resourceId ||
      selector === path.basename(entry.directory) ||
      aliases.some((alias) => alias.kind === entry.kind && alias.source.repository === entry.source?.repository),
  );
  if (!selected.length) throw new Error(`No registered resource matches ${selector}`);
  if (selector && selected.length > 1)
    throw new Error(`Ambiguous resource ${selector}; use its resource ID or directory`);
  const resources = [];
  for (const entry of selected) {
    try {
      const root = path.join(context.workbench, entry.directory);
      if ((await realpath(root)) !== root) throw new Error("Managed checkout crosses a symlink");
      resources.push({ ...entry, ...(await inspectAuthoringRepository(root)) });
    } catch (error) {
      resources.push({ ...entry, error: message(error) });
    }
  }
  return { workbench: context.workbench, verificationEvidence: false, resources };
}