/**
 * @fileoverview Centralized buffer size limits for memory management.
 *
 * These constants define the maximum sizes for various buffers throughout
 * Codeman. Consolidating them here ensures consistent limits and makes
 * it easy to tune memory usage.
 *
 * Memory Budget Rationale (for 20 concurrent sessions):
 * - Terminal buffer: 32MB max × 20 = 640MB worst case
 * - Text output: 1MB max × 20 = 20MB worst case
 * - Messages: ~1KB each × 1000 × 20 = 20MB worst case
 *
 * @module config/buffer-limits
 */

import { DEFAULT_TERMINAL_BUFFER_MAX_BYTES, DEFAULT_TERMINAL_BUFFER_TRIM_BYTES } from './terminal-history.js';

// ============================================================================
// Terminal Buffer Limits
// ============================================================================

/**
 * Maximum terminal buffer size in characters.
 * Contains raw terminal output with ANSI escape sequences.
 * Sourced from terminal-history config (env/settings overridable).
 * Override: CODEMAN_MAX_TERMINAL_BUFFER (bytes)
 */
export const MAX_TERMINAL_BUFFER_SIZE = DEFAULT_TERMINAL_BUFFER_MAX_BYTES;

/**
 * Size to trim terminal buffer to when max is exceeded.
 * Keeps the most recent portion to preserve context.
 * Override: CODEMAN_TRIM_TERMINAL_TO (bytes)
 */
export const TRIM_TERMINAL_TO = DEFAULT_TERMINAL_BUFFER_TRIM_BYTES;

// ============================================================================
// Text Output Buffer Limits
// ============================================================================

/**
 * Maximum text output buffer size in characters.
 * Contains ANSI-stripped text for search and analysis.
 * Override: CODEMAN_MAX_TEXT_OUTPUT (bytes)
 */
export const MAX_TEXT_OUTPUT_SIZE = parseInt(process.env.CODEMAN_MAX_TEXT_OUTPUT || '') || 1 * 1024 * 1024;

/**
 * Size to trim text output buffer to when max is exceeded.
 * Override: CODEMAN_TRIM_TEXT_TO (bytes)
 */
export const TRIM_TEXT_TO = parseInt(process.env.CODEMAN_TRIM_TEXT_TO || '') || 768 * 1024;

// ============================================================================
// Message Buffer Limits
// ============================================================================

/**
 * Maximum number of Claude JSON messages to keep in memory per session.
 * Older messages are discarded when limit is exceeded.
 * Override: CODEMAN_MAX_MESSAGES (count)
 */
export const MAX_MESSAGES = parseInt(process.env.CODEMAN_MAX_MESSAGES || '') || 1000;

// ============================================================================
// Line Buffer Limits
// ============================================================================

/**
 * Maximum line buffer size in characters.
 * Prevents unbounded growth for extremely long lines without newlines.
 */
export const MAX_LINE_BUFFER_SIZE = 64 * 1024; // 64KB

// ============================================================================
// Respawn Controller Buffer Limits
// ============================================================================

/**
 * Maximum respawn controller buffer size.
 * Smaller than session buffer since it's only used for idle detection.
 */
export const MAX_RESPAWN_BUFFER_SIZE = 1 * 1024 * 1024; // 1MB

/**
 * Size to trim respawn buffer to when max is exceeded.
 */
export const TRIM_RESPAWN_BUFFER_TO = 512 * 1024; // 512KB

// ============================================================================
// File Peek Limits
// ============================================================================

/**
 * Maximum bytes to read when peeking at the beginning of a file.
 * Used with `createReadStream({ end })` (inclusive) to read the first 8KB,
 * which is enough to extract metadata from the first few JSONL lines.
 */
export const FILE_PEEK_BYTES = 8 * 1024 - 1; // 8KB (inclusive end offset)

// ============================================================================
// Paste-Image Upload Limits
// ============================================================================

/**
 * Maximum size (bytes) of a single image uploaded via POST
 * /api/sessions/:id/paste-image. The mobile picker / drag-drop / paste paths
 * send one file per request (the client uploads up to MAX_PASTE_IMAGES of them
 * per batch), so this caps each individual file, not the batch. Generous enough
 * for full-resolution phone photos and large screenshots; the client downscales
 * very large images before upload, so legitimate uploads land well under this.
 * Override: CODEMAN_MAX_PASTE_IMAGE_BYTES (bytes)
 */
export const MAX_PASTE_IMAGE_BYTES = parseInt(process.env.CODEMAN_MAX_PASTE_IMAGE_BYTES || '') || 50 * 1024 * 1024; // 50MB

// ============================================================================
// File Download Limits
// ============================================================================

/**
 * Parse a byte-limit env var, where `0` explicitly means "no limit".
 *
 * The `parseInt(...) || default` idiom used elsewhere in this file cannot
 * express that: it treats 0 as falsy and silently restores the default.
 */
function parseByteLimitEnv(raw: string | undefined, fallback: number): number {
  if (raw === undefined || raw.trim() === '') return fallback;
  const parsed = Number.parseInt(raw, 10);
  if (!Number.isFinite(parsed) || parsed < 0) return fallback;
  return parsed;
}

/**
 * Maximum size (bytes) of a file served by the raw/download file routes:
 * `GET /api/sessions/:id/file-raw` (the Files panel's download link and the
 * file-preview overlay), the attachment `/raw` route, and `GET /api/download`.
 *
 * ⚠️ This is a sanity bound, NOT memory protection. All three bodies are
 * STREAMED and `Range`-aware (`sendFileBody` in file-routes.ts), so a large
 * file costs one read stream rather than its size in RSS. The historical 50MB
 * cap predates that streaming rewrite and its "prevent memory exhaustion"
 * comment described a `readFile()` that no longer exists — all it did was
 * refuse legitimate downloads of build artifacts, videos and archives.
 *
 * Set `CODEMAN_MAX_DOWNLOAD_BYTES=0` to remove the cap entirely.
 * Override: CODEMAN_MAX_DOWNLOAD_BYTES (bytes)
 */
export const MAX_FILE_DOWNLOAD_BYTES = parseByteLimitEnv(
  process.env.CODEMAN_MAX_DOWNLOAD_BYTES,
  2 * 1024 * 1024 * 1024 // 2GB
);

/** True when `size` exceeds the download cap (a cap of 0 means unlimited). */
export function exceedsDownloadLimit(size: number): boolean {
  return MAX_FILE_DOWNLOAD_BYTES > 0 && size > MAX_FILE_DOWNLOAD_BYTES;
}

/** Human-readable "File too large (…)" message for a refused download. */
export function downloadTooLargeMessage(size: number): string {
  return `File too large (${Math.round(size / 1024 / 1024)}MB > ${Math.round(MAX_FILE_DOWNLOAD_BYTES / 1024 / 1024)}MB limit). Raise or remove it with CODEMAN_MAX_DOWNLOAD_BYTES (0 = unlimited).`;
}