import { promises as fs } from 'fs';
import { randomBytes } from 'crypto';
import path from 'path';
import type { Sql } from '../db.js';

// v1.13.5: opencode-style truncation storage. When a tool slice would cut
// content the model might still want, we store the full text on tmpfs and
// hand the model an opaque id. view_truncated_output(id) retrieves it.
//
// Tmpfs path means full content vanishes on container restart; chats that
// outlive a restart lose retrieval (acceptable — the user has usually moved
// on or the data is stale). 7-day TTL + orphan reap bound disk growth via
// the periodic sweeper in index.ts.

export const TRUNCATION_DIR = process.env.BOOCODE_TRUNCATION_DIR ?? '/tmp/boocode-truncations';
export const TRUNCATION_TTL_MS = 7 * 24 * 60 * 60 * 1000;
// Matches view_file's MAX_FILE_BYTES — anything bigger was already refused
// at the source tool's size check, so we never see it here.
export const MAX_TRUNCATION_BYTES = 5 * 1024 * 1024;

const ID_RE = /^tr_[0-9a-v]{12}$/;

let dirEnsured = false;
async function ensureDir(): Promise<void> {
  if (dirEnsured) return;
  await fs.mkdir(TRUNCATION_DIR, { recursive: true, mode: 0o700 });
  dirEnsured = true;
}

// 12 base32 chars ≈ 60 bits of entropy. Collision probability across a
// 7-day window with ~thousands of truncations is essentially zero.
function newId(): string {
  const buf = randomBytes(8);
  const alphabet = '0123456789abcdefghijklmnopqrstuv';
  let out = 'tr_';
  for (const byte of buf) {
    out += alphabet[byte & 0x1f];
    out += alphabet[(byte >> 3) & 0x1f];
  }
  return out.slice(0, 15);
}

function idToPath(id: string): string {
  // Defense-in-depth: the model never supplies a path component (only ids),
  // but a malformed id from anywhere else shouldn't escape TRUNCATION_DIR.
  if (!ID_RE.test(id)) {
    throw new Error(`Invalid truncation id: ${id}`);
  }
  return path.join(TRUNCATION_DIR, id);
}

export async function storeTruncation(fullContent: string): Promise<string> {
  const bytes = Buffer.byteLength(fullContent, 'utf8');
  if (bytes > MAX_TRUNCATION_BYTES) {
    throw new Error(`Truncation content ${bytes}B exceeds ${MAX_TRUNCATION_BYTES}B cap`);
  }
  await ensureDir();
  const id = newId();
  await fs.writeFile(idToPath(id), fullContent, { encoding: 'utf8', mode: 0o600 });
  return id;
}

export async function readTruncation(id: string): Promise<string | null> {
  if (!ID_RE.test(id)) return null;
  try {
    return await fs.readFile(idToPath(id), { encoding: 'utf8' });
  } catch (err) {
    if ((err as NodeJS.ErrnoException).code === 'ENOENT') return null;
    throw err;
  }
}

// Wrap a tool's output. If wasTruncated, stash the full content on tmpfs
// and return its id alongside the sliced view the tool would have returned.
// Storage failure (disk full, permission denied) is non-fatal — the sliced
// view ships without an outputPath, which is exactly what the tool returned
// before v1.13.5. Same goes for content over MAX_TRUNCATION_BYTES.
export async function truncateIfNeeded(args: {
  fullContent: string;
  slicedContent: string;
  wasTruncated: boolean;
}): Promise<{ content: string; truncated: boolean; outputPath?: string }> {
  if (!args.wasTruncated) {
    return { content: args.slicedContent, truncated: false };
  }
  const bytes = Buffer.byteLength(args.fullContent, 'utf8');
  if (bytes > MAX_TRUNCATION_BYTES) {
    return { content: args.slicedContent, truncated: true };
  }
  try {
    const outputPath = await storeTruncation(args.fullContent);
    return { content: args.slicedContent, truncated: true, outputPath };
  } catch {
    return { content: args.slicedContent, truncated: true };
  }
}

// Periodic cleanup. Called from index.ts's sweep interval (v1.13.3 cadence).
// Pass 1: TTL — anything older than TRUNCATION_TTL_MS is gone.
// Pass 2: orphans — files with no live message_parts.payload->'output'->>'outputPath'
// reference. Catches the case where a part referencing an outputPath got
// hidden by prune (v1.13.4) and the file is now unreachable.
export async function cleanupTruncations(args: {
  sql: Sql;
  log: { warn: (obj: object, msg: string) => void; error: (obj: object, msg: string) => void };
}): Promise<{ ttlReaped: number; orphanReaped: number }> {
  await ensureDir();
  const cutoff = Date.now() - TRUNCATION_TTL_MS;
  let ttlReaped = 0;
  let orphanReaped = 0;

  let entries: string[];
  try {
    entries = await fs.readdir(TRUNCATION_DIR);
  } catch (err) {
    args.log.error({ err }, 'cleanupTruncations readdir failed');
    return { ttlReaped, orphanReaped };
  }
  if (entries.length === 0) return { ttlReaped, orphanReaped };

  const survivors: string[] = [];
  for (const name of entries) {
    if (!ID_RE.test(name)) continue;
    const full = path.join(TRUNCATION_DIR, name);
    try {
      const stat = await fs.stat(full);
      if (stat.mtimeMs < cutoff) {
        await fs.unlink(full);
        ttlReaped += 1;
      } else {
        survivors.push(name);
      }
    } catch {
      // File vanished between readdir and stat — fine.
    }
  }

  if (survivors.length === 0) {
    if (ttlReaped > 0) {
      args.log.warn({ ttlReaped, orphanReaped: 0 }, 'cleanupTruncations reaped files');
    }
    return { ttlReaped, orphanReaped: 0 };
  }

  // outputPath rides inside the tool_result part's payload.output object
  // (see partsFromToolMessage in inference/parts.ts), so the json path is
  // payload->'output'->>'outputPath' rather than top-level.
  const referenced = await args.sql<{ output_path: string }[]>`
    SELECT DISTINCT p.payload->'output'->>'outputPath' AS output_path
    FROM message_parts p
    WHERE p.kind = 'tool_result'
      AND p.payload->'output' ? 'outputPath'
      AND p.payload->'output'->>'outputPath' = ANY(${survivors})
  `;
  const live = new Set(referenced.map((r) => r.output_path));
  for (const name of survivors) {
    if (live.has(name)) continue;
    try {
      await fs.unlink(path.join(TRUNCATION_DIR, name));
      orphanReaped += 1;
    } catch {
      // ignore
    }
  }

  if (ttlReaped > 0 || orphanReaped > 0) {
    args.log.warn({ ttlReaped, orphanReaped }, 'cleanupTruncations reaped files');
  }
  return { ttlReaped, orphanReaped };
}