import fs from "node:fs";
import os from "node:os";
import path from "node:path";

import { resolveSessionTranscriptPath } from "../config/sessions.js";

export function readSessionMessages(
  sessionId: string,
  storePath: string | undefined,
  sessionFile?: string,
): unknown[] {
  const candidates = resolveSessionTranscriptCandidates(
    sessionId,
    storePath,
    sessionFile,
  );

  const filePath = candidates.find((p) => fs.existsSync(p));
  if (!filePath) return [];

  const lines = fs.readFileSync(filePath, "utf-8").split(/\r?\n/);
  const messages: unknown[] = [];
  for (const line of lines) {
    if (!line.trim()) continue;
    try {
      const parsed = JSON.parse(line);
      if (parsed?.message) {
        messages.push(parsed.message);
      }
    } catch {
      // ignore bad lines
    }
  }
  return messages;
}

export function resolveSessionTranscriptCandidates(
  sessionId: string,
  storePath: string | undefined,
  sessionFile?: string,
  agentId?: string,
): string[] {
  const candidates: string[] = [];
  if (sessionFile) candidates.push(sessionFile);
  if (storePath) {
    const dir = path.dirname(storePath);
    candidates.push(path.join(dir, `${sessionId}.jsonl`));
  }
  if (agentId) {
    candidates.push(resolveSessionTranscriptPath(sessionId, agentId));
  }
  candidates.push(
    path.join(os.homedir(), ".clawdbot", "sessions", `${sessionId}.jsonl`),
  );
  return candidates;
}

export function archiveFileOnDisk(filePath: string, reason: string): string {
  const ts = new Date().toISOString().replaceAll(":", "-");
  const archived = `${filePath}.${reason}.${ts}`;
  fs.renameSync(filePath, archived);
  return archived;
}

function jsonUtf8Bytes(value: unknown): number {
  try {
    return Buffer.byteLength(JSON.stringify(value), "utf8");
  } catch {
    return Buffer.byteLength(String(value), "utf8");
  }
}

export function capArrayByJsonBytes<T>(
  items: T[],
  maxBytes: number,
): { items: T[]; bytes: number } {
  if (items.length === 0) return { items, bytes: 2 };
  const parts = items.map((item) => jsonUtf8Bytes(item));
  let bytes = 2 + parts.reduce((a, b) => a + b, 0) + (items.length - 1);
  let start = 0;
  while (bytes > maxBytes && start < items.length - 1) {
    bytes -= parts[start] + 1;
    start += 1;
  }
  const next = start > 0 ? items.slice(start) : items;
  return { items: next, bytes };
}