import { existsSync, readdirSync } from "node:fs";
import { execFileSync } from "node:child_process";
import { dirname, extname, join, resolve } from "node:path";
import type { PromptSignals, RepositorySignals } from "./types.js";

const filePathPattern = /\b(?:[\w.-]+\/)*[\w.-]+\.(?:[cm]?[jt]sx?|json|md|py|go|rs|java|rb|php|css|html|yaml|yml)\b/gi;

export function collectPromptSignals(prompt: string): PromptSignals {
  return { mentionedFileCount: new Set(prompt.match(filePathPattern) ?? []).size };
}

const SIGNAL_CACHE_TTL_MS = 10_000;
const MAX_FILES = 10_000;
const MAX_SCAN_MS = 50;
const ignoredDirectories = new Set([".git", ".pi", "node_modules"]);
const languageByExtension: Readonly<Record<string, string>> = {
  ".ts": "ts", ".tsx": "ts", ".js": "js", ".jsx": "js", ".mjs": "js", ".cjs": "js",
  ".py": "py", ".go": "go", ".rs": "rs", ".java": "java", ".rb": "rb", ".php": "php",
  ".css": "css", ".html": "html", ".json": "json", ".md": "md", ".yml": "yaml", ".yaml": "yaml",
};
let repositoryCache: { cwd: string; expiresAt: number; signals: RepositorySignals } | undefined;

export function clearRepositorySignalCache(): void {
  repositoryCache = undefined;
}

function projectRoot(cwd: string): string {
  let current = resolve(cwd);
  while (true) {
    if (existsSync(join(current, ".git"))) return current;
    const parent = dirname(current);
    if (parent === current) return resolve(cwd);
    current = parent;
  }
}

function gitDiffSize(cwd: string): number | undefined {
  try {
    const output = execFileSync("git", ["diff", "--numstat"], { cwd, encoding: "utf8", timeout: 100, stdio: ["ignore", "pipe", "ignore"] });
    return output.split("\n").reduce((total, line) => {
      const [added, removed] = line.split("\t");
      return total + (Number(added) || 0) + (Number(removed) || 0);
    }, 0);
  } catch {
    return undefined;
  }
}

/** Bounded, best-effort filesystem inspection; failures intentionally return neutral signals. */
export function collectRepositorySignals(cwd: string, now = Date.now()): RepositorySignals {
  if (repositoryCache?.cwd === cwd && repositoryCache.expiresAt > now) return repositoryCache.signals;
  try {
    const root = projectRoot(cwd);
    const deadline = Date.now() + MAX_SCAN_MS;
    const directories = [root];
    const languageMix: Record<string, number> = {};
    let fileCount = 0;
    while (directories.length && fileCount < MAX_FILES && Date.now() <= deadline) {
      const directory = directories.pop()!;
      for (const entry of readdirSync(directory, { withFileTypes: true })) {
        if (entry.isDirectory()) {
          if (!ignoredDirectories.has(entry.name)) directories.push(join(directory, entry.name));
        } else if (entry.isFile()) {
          fileCount += 1;
          const language = languageByExtension[extname(entry.name).toLowerCase()];
          if (language) languageMix[language] = (languageMix[language] ?? 0) + 1;
          if (fileCount >= MAX_FILES || Date.now() > deadline) break;
        }
      }
    }
    const signals: RepositorySignals = { projectRoot: root, fileCount, languageMix, diffSize: gitDiffSize(root) };
    repositoryCache = { cwd, expiresAt: now + SIGNAL_CACHE_TTL_MS, signals };
    return signals;
  } catch {
    return {};
  }
}

export function repositorySignalScore(signals: RepositorySignals = {}): number {
  let score = 0;

  if ((signals.fileCount ?? 0) >= 10_000) score += 15;
  else if ((signals.fileCount ?? 0) >= 1_000) score += 10;
  if ((signals.diffSize ?? 0) >= 500) score += 10;
  if ((signals.promptFileCount ?? 0) >= 4) score += 10;
  if (Object.keys(signals.languageMix ?? {}).length >= 4) score += 5;

  return Math.min(score, 30);
}