import { readdirSync, readFileSync, existsSync, statSync } from 'node:fs';
import { join } from 'node:path';
import { DATA_PATH } from '../../data-path';

// ── Claude session store (source of truth) ──
// The `claude` CLI persists every session as a JSONL transcript at
//   $HOME/.claude/projects/<slug>/<session-uuid>.jsonl
// where <slug> is the working directory with every non-alphanumeric char replaced by '-'.
// A user's claude process runs with HOME = DATA_PATH/<email>/home (see sidecar/claude/user-instance.ts),
// so we read transcripts from there. We never maintain our own copy — Claude's files are authoritative.

/** Dedicated working directory for /chat sessions, so they form their own Claude "project" group. */
export const getClaudeSessionsCwd = (email: string): string => join(DATA_PATH, email, 'claude_sessions');

const claudeProjectsDir = (email: string): string => join(DATA_PATH, email, 'home', '.claude', 'projects');

/** Claude's folder name for a working directory. */
export const projectSlug = (cwd: string): string => cwd.replace(/[^a-zA-Z0-9]/g, '-');

export type ClaudeSessionSummary = {
  id: string; // session uuid (= transcript filename)
  title: string; // first human message, trimmed
  cwd: string;
  createdAt: string; // ISO, first entry
  updatedAt: string; // ISO, last entry
  messageCount: number; // human + assistant turns
};

/** Pull the plain text out of a transcript entry's `message.content` (string or content-block array). */
function entryText(message: unknown): string {
  if (!message || typeof message !== 'object') return '';
  const content = (message as { content?: unknown }).content;
  if (typeof content === 'string') return content;
  if (Array.isArray(content)) {
    return content
      .map((block) => (block && typeof block === 'object' && (block as { type?: string }).type === 'text' ? (block as { text?: string }).text ?? '' : ''))
      .join('')
      .trim();
  }
  return '';
}

type Entry = {
  type?: string;
  timestamp?: string;
  sessionId?: string;
  cwd?: string;
  message?: { role?: string; content?: unknown };
  isMeta?: boolean;
};

function summarizeTranscript(filePath: string, id: string): ClaudeSessionSummary | null {
  let raw: string;
  try {
    raw = readFileSync(filePath, 'utf-8');
  } catch {
    return null;
  }

  let title = '';
  let cwd = '';
  let firstTs = '';
  let lastTs = '';
  let messageCount = 0;

  for (const line of raw.split('\n')) {
    if (!line.trim()) continue;
    let entry: Entry;
    try {
      entry = JSON.parse(line) as Entry;
    } catch {
      continue;
    }
    if (entry.cwd && !cwd) cwd = entry.cwd;
    if (entry.timestamp) {
      if (!firstTs) firstTs = entry.timestamp;
      lastTs = entry.timestamp;
    }
    if (entry.type === 'user' || entry.type === 'assistant') {
      messageCount += 1;
      if (!title && entry.type === 'user' && !entry.isMeta) {
        title = entryText(entry.message).split('\n')[0]!.trim();
      }
    }
  }

  const mtime = statSync(filePath).mtime.toISOString();
  return {
    id,
    title: title || '(untitled)',
    cwd,
    createdAt: firstTs || mtime,
    updatedAt: lastTs || mtime,
    messageCount,
  };
}

/** List sessions Claude has stored for a given working directory, newest first. */
export function listClaudeSessions(email: string, cwd: string): ClaudeSessionSummary[] {
  const dir = join(claudeProjectsDir(email), projectSlug(cwd));
  if (!existsSync(dir)) return [];

  const sessions: ClaudeSessionSummary[] = [];
  for (const file of readdirSync(dir)) {
    if (!file.endsWith('.jsonl')) continue;
    const summary = summarizeTranscript(join(dir, file), file.replace(/\.jsonl$/, ''));
    if (summary) sessions.push(summary);
  }
  return sessions.sort((a, b) => b.updatedAt.localeCompare(a.updatedAt));
}