/**
 * Shared work/ solution picker for the test and submit entries: fuzzy-select
 * a solution file, then hand it to leetcode-cli.
 *
 * Every bucket is listed — a 3-day or 7-day re-solve is tested and submitted
 * exactly like a first solve — and the hint says which one a file belongs to.
 * The db's per-solution timestamps are keyed by LC number, so the buckets of
 * one problem share them.
 *
 * Every run backfills the db's solutions table with created_at (from the
 * file's birthtime, mtime when the filesystem has none) so ordering works for
 * files that predate the db. Files git reports as modified, added or
 * untracked come first, newest edit first — the problem being worked on is
 * the focused option, so Enter runs it without a search. The rest are ordered
 * per command — test lists the most recently tested first (never-tested
 * after, by name); submit lists the most recently created first. Nothing is
 * ever hidden. Exit 0 of leetcode-cli stamps last_tested / last_submitted.
 *
 * Library: side-effect-free on import — nothing scans the filesystem until
 * runOnSolution() is called.
 */
import { autocomplete, cancel, isCancel, log } from "@clack/prompts";
import { statSync } from "node:fs";
import { basename, join, relative } from "node:path";
import { problemDb } from "./db";
import { ROOT, WORK as WORK_DIR, parseWorkPath } from "./work";

/** Leading LC number of a work/ file, or undefined for unnumbered names. */
function lcNumber(rel: string): number | undefined {
  const m = basename(rel).match(/^(\d+)\./);
  return m ? Number(m[1]) : undefined;
}

/**
 * work/-relative paths of solutions git sees as modified, added or untracked,
 * mapped to their mtime. Empty outside a git checkout.
 */
function dirtySolutions(scanned: Set<string>): Map<string, number> {
  const git = Bun.spawnSync(
    ["git", "status", "--porcelain", "-z", "--untracked-files=all", "--", WORK_DIR],
    { cwd: ROOT },
  );
  const dirty = new Map<string, number>();
  if (!git.success) return dirty;
  const entries = git.stdout.toString().split("\0");
  for (let i = 0; i < entries.length; i++) {
    const entry = entries[i]!;
    // renames/copies carry their source path as the next entry; skip it
    if (/[RC]/.test(entry.slice(0, 2))) i++;
    const rel = relative(WORK_DIR, join(ROOT, entry.slice(3)));
    // deletions and non-solution files are not in the scan
    if (scanned.has(rel)) dirty.set(rel, statSync(join(WORK_DIR, rel)).mtimeMs);
  }
  return dirty;
}

/** Fuzzy-pick a solution under work/ and run `leetcode <command>` on it. */
export async function runOnSolution(
  command: "test" | "submit",
  message: string,
): Promise<never> {
  const db = problemDb();

  const scanned = [
    ...new Bun.Glob("**/*.{js,ts,py,java,c,cpp,go,rs,rb,swift,kt,cs}").scanSync(
      { cwd: WORK_DIR },
    ),
  ];

  // register creation times so files older than the db still sort correctly
  for (const f of scanned) {
    const num = lcNumber(f);
    if (num === undefined) continue;
    const stat = statSync(join(WORK_DIR, f));
    db.ensureSolution(
      num,
      new Date(stat.birthtimeMs || stat.mtimeMs).toISOString(),
    );
  }
  const activity = db.solutionActivity();

  // test → most recently tested first; submit → most recently created first
  const sortKey = (f: string) => {
    const num = lcNumber(f);
    const row = num === undefined ? undefined : activity.get(num);
    return (command === "test" ? row?.lastTested : row?.createdAt) ?? undefined;
  };

  const dirty = dirtySolutions(new Set(scanned));
  const files = scanned.sort((a, b) => {
    const ma = dirty.get(a);
    const mb = dirty.get(b);
    if (ma !== mb) {
      if (ma === undefined) return 1;
      if (mb === undefined) return -1;
      return mb - ma;
    }
    const ka = sortKey(a);
    const kb = sortKey(b);
    if (ka !== kb) {
      if (ka === undefined) return 1;
      if (kb === undefined) return -1;
      return kb.localeCompare(ka); // ISO timestamps: lexicographic = chronological
    }
    return a.localeCompare(b, undefined, { numeric: true });
  });

  if (files.length === 0) {
    log.error(
      `No solution files found in ${relative(process.cwd(), WORK_DIR)}/`,
    );
    process.exit(1);
  }

  const picked = await autocomplete<string>({
    message,
    placeholder: "Type to search...",
    maxItems: 12,
    options: files.map((f) => {
      const parsed = parseWorkPath(f);
      const stage =
        parsed?.bucket === 1 ? "first solve" : `${parsed?.bucket}-day review`;
      return {
        value: f,
        label: basename(f),
        hint: parsed
          ? `${dirty.has(f) ? "uncommitted · " : ""}${stage} · ${parsed.difficulty} · ${parsed.category}`
          : f,
      };
    }),
    filter: (search, option) => {
      const haystack = option.value.toLowerCase();
      return search
        .toLowerCase()
        .split(/\s+/)
        .every((token) => haystack.includes(token));
    },
  });

  if (isCancel(picked)) {
    cancel("Nothing selected.");
    process.exit(0);
  }

  const proc = Bun.spawn(
    [
      // bun installs workspace-dep bins into this package's node_modules, not the root's
      join(import.meta.dir, "node_modules", ".bin", "leetcode"),
      command,
      join(WORK_DIR, picked),
    ],
    { cwd: ROOT, stdio: ["inherit", "inherit", "inherit"] },
  );
  const code = await proc.exited;
  const num = lcNumber(picked);
  if (code === 0 && num !== undefined) {
    if (command === "test") db.markTested(num);
    else db.markSubmitted(num);
  }
  db.close();
  process.exit(code);
}