/**
 * Repo registry for the multi-repo visualizer.
 *
 * The visualizer can serve several repos' trace DBs from one process. A repo
 * is a slug → sssf.db mapping, declared in a JSON file:
 *
 *   [
 *     { "slug": "tailsandstays", "name": "Tails & Stays",
 *       "db": "/home/ima/projects/tailsandstays/adws/adw_data/sssf.db" },
 *     { "slug": "mempalace", "name": "MemPalace",
 *       "db": "/home/ima/projects/mempalace/adws/adw_data/sssf.db" }
 *   ]
 *
 * Point the server at it with SSSF_REPOS=/path/to/repos.json. When SSSF_REPOS
 * is unset the server auto-discovers repos under a projects root (default
 * ~/projects, override with SSSF_PROJECTS_ROOT) by scanning for a trace db at
 * <root>/<dir>/adws/adw_data/sssf.db. If nothing is discovered it falls back to
 * the single-repo behaviour (--db / SSSF_DB / <cwd>/adws/adw_data/sssf.db)
 * under a slug derived from the repo dir name, so the original single-repo
 * deployment keeps working.
 */
import { existsSync, readdirSync } from "node:fs";
import { homedir } from "node:os";
import { basename, dirname, isAbsolute, join, resolve } from "node:path";
import { SssfDb, resolveDbPath } from "./db.ts";

export interface RepoEntry {
  slug: string;
  name: string;
  db: string;
}

export interface RepoRuntime {
  slug: string;
  name: string;
  db: SssfDb;
}

const SAFE_SLUG = /^[A-Za-z0-9._-]+$/;

function isSafeSlug(slug: string): boolean {
  return SAFE_SLUG.test(slug) && slug !== "." && slug !== "..";
}

/** Derive a display slug from a db path: <repo>/adws/adw_data/sssf.db → repo dir name. */
function slugFromDb(dbPath: string): string {
  // adw_data → adws → repo root
  const repoDir = dirname(dirname(dirname(dbPath)));
  const name = basename(repoDir);
  return name && isSafeSlug(name) ? name : "default";
}

async function loadReposFile(path: string): Promise<RepoEntry[]> {
  const raw = Bun.file(path);
  if (!existsSync(path)) {
    throw new Error(`SSSF_REPOS file not found: ${path}`);
  }
  const data = JSON.parse(await raw.text()) as unknown;
  if (!Array.isArray(data)) {
    throw new Error(`SSSF_REPOS file must be a JSON array of { slug, name, db }`);
  }
  const entries: RepoEntry[] = [];
  const seen = new Set<string>();
  for (const item of data) {
    const entry = item as Partial<RepoEntry>;
    if (typeof entry.slug !== "string" || !isSafeSlug(entry.slug)) {
      throw new Error(`invalid repo slug: ${String(entry.slug)}`);
    }
    if (typeof entry.db !== "string") {
      throw new Error(`repo "${entry.slug}" is missing a db path`);
    }
    if (seen.has(entry.slug)) {
      throw new Error(`duplicate repo slug: ${entry.slug}`);
    }
    seen.add(entry.slug);
    const db = isAbsolute(entry.db) ? entry.db : resolve(dirname(path), entry.db);
    entries.push({
      slug: entry.slug,
      name: typeof entry.name === "string" && entry.name ? entry.name : entry.slug,
      db,
    });
  }
  if (entries.length === 0) {
    throw new Error("SSSF_REPOS file declares no repos");
  }
  return entries;
}

/**
 * Auto-discover repos under a projects root by scanning for a trace db at
 * <root>/<dir>/adws/adw_data/sssf.db. Used when SSSF_REPOS is unset so new
 * repos appear without editing a registry file. The root defaults to
 * ~/projects and can be overridden with SSSF_PROJECTS_ROOT.
 */
function discoverRepos(root: string): RepoEntry[] {
  if (!existsSync(root)) {
    return [];
  }
  const entries: RepoEntry[] = [];
  for (const name of readdirSync(root, { withFileTypes: true })) {
    if (!name.isDirectory() || name.name.startsWith(".")) {
      continue;
    }
    const db = join(root, name.name, "adws", "adw_data", "sssf.db");
    if (existsSync(db) && isSafeSlug(name.name)) {
      entries.push({ slug: name.name, name: name.name, db });
    }
  }
  return entries;
}

/**
 * Build the repo registry. The first repo is served under the legacy
 * unprefixed /api routes (the single repo in single-repo mode, or the first
 * repo in multi-repo mode).
 */
export async function buildRepos(): Promise<{ repos: RepoRuntime[] }> {
  const reposFile = process.env.SSSF_REPOS;
  const entries: RepoEntry[] = reposFile
    ? await loadReposFile(reposFile)
    : discoverRepos(process.env.SSSF_PROJECTS_ROOT ?? join(homedir(), "projects"));
  if (entries.length === 0) {
    // No discovered repos — fall back to the single-repo behaviour so the
    // original deployment (--db / SSSF_DB / <cwd>/adws/adw_data/sssf.db) works.
    entries.push({ slug: slugFromDb(resolveDbPath()), name: "", db: resolveDbPath() });
  }

  const repos: RepoRuntime[] = [];
  for (const entry of entries) {
    let db: SssfDb;
    try {
      db = new SssfDb(entry.db);
    } catch (error) {
      console.error(`[sssf] repo "${entry.slug}": ${(error as Error).message}`);
      continue;
    }
    repos.push({ slug: entry.slug, name: entry.name, db });
  }

  if (repos.length === 0) {
    console.error("[sssf] no repos could be opened — exiting");
    process.exit(1);
  }

  return { repos };
}