import { existsSync, readFileSync } from "node:fs";
import { resolve, join, dirname } from "node:path";
import { homedir } from "node:os";
import type { InboxConfig } from "./types.ts";

export const DEFAULTS: InboxConfig = {
  inbox: "default",
  dataDir: join(homedir(), ".pi", "inbox"),
  pollIntervalMs: 2000,
  maxReplayMessages: 20,
};

function expandHome(path: string): string {
  if (path === "~") {
    return homedir();
  }
  if (path.startsWith("~/")) {
    return join(homedir(), path.slice(2));
  }
  return path;
}

function loadProjectConfig(cwd: string): Partial<InboxConfig> | null {
  let dir = resolve(cwd);
  const root = resolve("/");
  while (dir !== root) {
    try {
      const projectConfigPath = join(dir, ".pi", "inbox.json");
      if (existsSync(projectConfigPath)) {
        const raw = readFileSync(projectConfigPath, "utf-8");
        return JSON.parse(raw) as Partial<InboxConfig>;
      }
    } catch {
      // invalid or unreadable
    }
    const parent = dirname(dir);
    if (parent === dir) break;
    dir = parent;
  }
  return null;
}

function loadGlobalConfig(): Partial<InboxConfig> | null {
  try {
    const globalConfigPath = join(homedir(), ".pi", "agent", "inbox.json");
    if (existsSync(globalConfigPath)) {
      const raw = readFileSync(globalConfigPath, "utf-8");
      return JSON.parse(raw) as Partial<InboxConfig>;
    }
  } catch {
    // not found or invalid
  }
  return null;
}

export function getDataDir(config: InboxConfig): string {
  return resolve(expandHome(config.dataDir));
}

export function loadConfig(cwd: string, cliOverrides?: Partial<InboxConfig>): InboxConfig {
  const project = loadProjectConfig(cwd) ?? {};
  const global = loadGlobalConfig() ?? {};

  // Priority: CLI > project > global > defaults
  return {
    inbox: cliOverrides?.inbox ?? project.inbox ?? global.inbox ?? DEFAULTS.inbox,
    dataDir: cliOverrides?.dataDir ?? project.dataDir ?? global.dataDir ?? DEFAULTS.dataDir,
    pollIntervalMs: cliOverrides?.pollIntervalMs ?? project.pollIntervalMs ?? global.pollIntervalMs ?? DEFAULTS.pollIntervalMs,
    maxReplayMessages: cliOverrides?.maxReplayMessages ?? project.maxReplayMessages ?? global.maxReplayMessages ?? DEFAULTS.maxReplayMessages,
  };
}