import { existsSync, readFileSync } from "node:fs";
import { homedir } from "node:os";
import { join, resolve } from "node:path";

export const DEFAULT_PORT = 37849;
export const DEFAULT_BIND = "127.0.0.1";
export const DEFAULT_HIDE_AFTER_MINUTES = 60 * 24;
export const DEFAULT_DELETE_AFTER_MINUTES = 60 * 24 * 7;
export const DEFAULT_SWEEP_INTERVAL_MINUTES = 60;

export interface FileConfig {
  port?: number;
  bind?: string;
  dbPath?: string;
  hideAfterMinutes?: number;
  deleteAfterMinutes?: number;
  sweepIntervalMinutes?: number;
}

export interface DaemonConfig {
  port: number;
  bind: string;
  dbPath: string;
  hideAfterMinutes: number;
  deleteAfterMinutes: number;
  sweepIntervalMinutes: number;
}

export function defaultDbPath(): string {
  return join(homedir(), ".claude-mailbox", "mailbox.db");
}

export function userConfigPath(): string {
  return join(homedir(), ".claude-mailbox", "mailbox.json");
}

export function machineConfigPath(): string | null {
  if (process.platform === "win32") {
    const programData = process.env["ProgramData"] ?? "C:\\ProgramData";
    return join(programData, "ClaudeMailbox", "mailbox.json");
  }
  if (process.platform === "darwin") {
    return "/Library/Application Support/ClaudeMailbox/mailbox.json";
  }
  return "/etc/claude-mailbox/mailbox.json";
}

function expandPath(p: string): string {
  let out = p;
  if (out.startsWith("~")) out = join(homedir(), out.slice(1));
  out = out.replace(/%([^%]+)%/g, (_, name) => process.env[name] ?? "");
  out = out.replace(/\$([A-Za-z_][A-Za-z0-9_]*)/g, (_, name) => process.env[name] ?? "");
  return resolve(out);
}

export function loadFileConfig(explicitPath?: string): FileConfig {
  const candidates: string[] = [];
  if (explicitPath) {
    if (!existsSync(explicitPath)) {
      throw new Error(`Config file not found: ${explicitPath}`);
    }
    candidates.push(explicitPath);
  } else {
    candidates.push(userConfigPath());
    const machine = machineConfigPath();
    if (machine) candidates.push(machine);
  }

  for (const path of candidates) {
    if (existsSync(path)) {
      const raw = readFileSync(path, "utf8");
      const parsed = JSON.parse(raw) as FileConfig;
      return {
        port: typeof parsed.port === "number" ? parsed.port : undefined,
        bind: typeof parsed.bind === "string" ? parsed.bind : undefined,
        dbPath: typeof parsed.dbPath === "string" ? parsed.dbPath : undefined,
        hideAfterMinutes:
          typeof parsed.hideAfterMinutes === "number" ? parsed.hideAfterMinutes : undefined,
        deleteAfterMinutes:
          typeof parsed.deleteAfterMinutes === "number" ? parsed.deleteAfterMinutes : undefined,
        sweepIntervalMinutes:
          typeof parsed.sweepIntervalMinutes === "number" ? parsed.sweepIntervalMinutes : undefined,
      };
    }
  }
  return {};
}

export interface ServeOverrides {
  port?: number;
  bind?: string;
  dbPath?: string;
  config?: string;
  hideAfterMinutes?: number;
  deleteAfterMinutes?: number;
  sweepIntervalMinutes?: number;
}

export function resolveConfig(overrides: ServeOverrides): DaemonConfig {
  const file = loadFileConfig(overrides.config);
  const port = overrides.port ?? file.port ?? DEFAULT_PORT;
  const bind = overrides.bind ?? file.bind ?? DEFAULT_BIND;
  const dbPathRaw = overrides.dbPath ?? file.dbPath ?? defaultDbPath();
  const hideAfterMinutes =
    overrides.hideAfterMinutes ?? file.hideAfterMinutes ?? DEFAULT_HIDE_AFTER_MINUTES;
  const deleteAfterMinutes =
    overrides.deleteAfterMinutes ?? file.deleteAfterMinutes ?? DEFAULT_DELETE_AFTER_MINUTES;
  const sweepIntervalMinutes =
    overrides.sweepIntervalMinutes ?? file.sweepIntervalMinutes ?? DEFAULT_SWEEP_INTERVAL_MINUTES;
  return {
    port,
    bind,
    dbPath: expandPath(dbPathRaw),
    hideAfterMinutes,
    deleteAfterMinutes,
    sweepIntervalMinutes,
  };
}

export function baseUrl(cfg: { port: number; bind: string }): string {
  return `http://${cfg.bind}:${cfg.port}`;
}