/**
 * Core library — orchestrates scan / check / update operations.
 */
import { readFileSync, readdirSync, statSync } from 'node:fs';
import { resolve, relative, extname } from 'node:path';
import type { Config, ScannedFile } from './types.js';
import { loadConfig, hasConfig } from './config.js';
import { scanFile } from './scanner.js';
import { generateDocs, readExistingDocs } from './doc-generator.js';
import { detectDrift, renderDriftReport } from './drift-detector.js';
import { getGitRoot, getAllTrackedFiles } from './git-tracker.js';

function shouldInclude(filePath: string, config: Config, cwd: string): boolean {
  const rel = relative(cwd, filePath);
  const ext = extname(filePath);
  if (!config.extensions.includes(ext)) return false;

  for (const exc of config.exclude) {
    const pattern = exc.replace(/\*\*/g, '.*').replace(/\*/g, '[^/]*');
    const re = new RegExp(pattern);
    if (re.test(rel)) return false;
  }

  for (const inc of config.include) {
    const incPath = resolve(cwd, inc);
    const incStat = statSync(incPath);
    if (incStat.isDirectory()) {
      if (rel.startsWith(relative(cwd, incPath))) return true;
    } else if (rel === relative(cwd, incPath)) {
      return true;
    }
  }
  return false;
}

export function scanProject(cwd: string): { scanned: ScannedFile[]; config: Config } {
  if (!hasConfig(cwd)) {
    throw new Error(`No ai-doc-drift.json found in ${cwd}. Run \`ai-doc-drift init\` first.`);
  }
  const config = loadConfig(cwd);
  const gitRoot = getGitRoot(cwd);
  let files: string[] = [];

  if (gitRoot) {
    files = getAllTrackedFiles(cwd)
      .map((f) => resolve(cwd, f))
      .filter((f) => shouldInclude(f, config, cwd));
  } else {
    // Fallback: recursive walk of include dirs
    const walk = (dir: string): string[] => {
      const entries = readdirSync(dir, { withFileTypes: true });
      const result: string[] = [];
      for (const e of entries) {
        const p = resolve(dir, e.name);
        if (e.isDirectory()) {
          const rel = relative(cwd, p);
          let excluded = false;
          for (const exc of config.exclude) {
            const pattern = exc.replace(/\*\*/g, '.*').replace(/\*/g, '[^/]*');
            const re = new RegExp(pattern);
            if (re.test(rel)) { excluded = true; break; }
          }
          if (!excluded) result.push(...walk(p));
        } else if (e.isFile() && shouldInclude(p, config, cwd)) {
          result.push(p);
        }
      }
      return result;
    };
    for (const inc of config.include) {
      const incPath = resolve(cwd, inc);
      if (statSync(incPath).isDirectory()) {
        files.push(...walk(incPath));
      } else {
        files.push(incPath);
      }
    }
  }

  const scanned: ScannedFile[] = [];
  for (const f of files) {
    try {
      const source = readFileSync(f, 'utf-8');
      scanned.push(scanFile(relative(cwd, f), source));
    } catch {
      // skip unreadable
    }
  }

  return { scanned, config };
}

export function runCheck(cwd: string): { report: string; exitCode: number } {
  const { scanned, config } = scanProject(cwd);
  const existing = readExistingDocs(resolve(cwd, config.docsDir));

  if (existing.size === 0) {
    return {
      report: `No existing docs found in ${config.docsDir}. Run \`ai-doc-drift scan\` first.`,
      exitCode: 1,
    };
  }

  const drift = detectDrift(scanned, existing);
  drift.projectName = config.projectName;
  const report = renderDriftReport(drift);
  return { report, exitCode: drift.items.length > 0 ? 2 : 0 };
}

export function runScan(cwd: string): { report: string; exitCode: number } {
  const { scanned, config } = scanProject(cwd);
  const written = generateDocs(scanned, config, cwd);
  return {
    report: `Generated docs:\n${written.map((w) => `  - ${w}`).join('\n')}`,
    exitCode: 0,
  };
}

export function runUpdate(cwd: string): { report: string; exitCode: number } {
  const { scanned, config } = scanProject(cwd);
  const written = generateDocs(scanned, config, cwd);
  return {
    report: `Updated docs:\n${written.map((w) => `  - ${w}`).join('\n')}`,
    exitCode: 0,
  };
}