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

export interface HookStdinPayload {
  session_id?: string;
  hook_event_name?: string;
  [key: string]: unknown;
}

export function parseHookStdin(raw: string | null | undefined): HookStdinPayload | null {
  if (!raw || !raw.trim()) return null;
  try {
    const parsed = JSON.parse(raw) as unknown;
    if (parsed && typeof parsed === "object") return parsed as HookStdinPayload;
    return null;
  } catch {
    return null;
  }
}

export function readStdinIfPiped(): string | null {
  if (process.stdin.isTTY) return null;
  try {
    return readFileSync(0, "utf8");
  } catch {
    return null;
  }
}

export function shortSessionId(sessionId: string): string {
  const hex = sessionId.replace(/[^0-9a-fA-F]/g, "").toLowerCase();
  if (hex.length >= 8) return hex.slice(0, 8);
  return sessionId.toLowerCase().replace(/[^a-z0-9]/g, "").slice(0, 8) || "00000000";
}

export function deriveSessionName(sessionId: string, base?: string | null): string {
  const short = shortSessionId(sessionId);
  const trimmed = (base ?? "").trim();
  if (trimmed) return `${trimmed}-${short}`;
  return `claude-${short}`;
}

export interface HookMessage {
  id: number;
  from: string;
  body: string;
  sentAt: string;
}

export function formatMessagesForHook(name: string, messages: HookMessage[]): string {
  if (messages.length === 0) return "";
  const header =
    messages.length === 1
      ? `You have 1 new mailbox message for "${name}":`
      : `You have ${messages.length} new mailbox messages for "${name}":`;
  const lines: string[] = [header, ""];
  for (const m of messages) {
    lines.push(`[#${m.id}] from ${m.from} (${m.sentAt}):`);
    for (const bodyLine of m.body.split(/\r?\n/)) {
      lines.push(`  ${bodyLine}`);
    }
    lines.push("");
  }
  return lines.join("\n").trimEnd() + "\n";
}

export type HookScope = "user" | "project";

export function settingsPathFor(scope: HookScope, cwd: string = process.cwd()): string {
  if (scope === "user") return join(homedir(), ".claude", "settings.json");
  return join(cwd, ".claude", "settings.json");
}

interface ClaudeHookCommand {
  type: "command";
  command: string;
  timeout?: number;
}

interface ClaudeHookGroup {
  matcher?: string;
  hooks: ClaudeHookCommand[];
}

interface ClaudeSettings {
  hooks?: Record<string, ClaudeHookGroup[]>;
  [key: string]: unknown;
}

const HOOK_EVENT = "UserPromptSubmit";

export function buildHookCommand(name: string, url?: string): string {
  const parts = ["claude-mailbox", "check", "--name", quoteIfNeeded(name), "--hook"];
  if (url) parts.push("--url", quoteIfNeeded(url));
  return parts.join(" ");
}

function quoteIfNeeded(value: string): string {
  if (/^[A-Za-z0-9._:/@\-]+$/.test(value)) return value;
  return `"${value.replace(/(["\\])/g, "\\$1")}"`;
}

function isOurHookCommand(command: string): boolean {
  const c = command.trim();
  return /(^|\W)claude-mailbox\s+check\s/.test(c) && /(^|\s)--hook(\s|$)/.test(c);
}

export function readSettings(path: string): ClaudeSettings {
  if (!existsSync(path)) return {};
  const raw = readFileSync(path, "utf8");
  if (!raw.trim()) return {};
  return JSON.parse(raw) as ClaudeSettings;
}

export function writeSettings(path: string, settings: ClaudeSettings): void {
  mkdirSync(dirname(path), { recursive: true });
  writeFileSync(path, JSON.stringify(settings, null, 2) + "\n", "utf8");
}

export interface PatchResult {
  changed: boolean;
  reason: "added" | "already-present" | "removed" | "not-present";
}

export function applyInstall(settings: ClaudeSettings, command: string): PatchResult {
  settings.hooks ??= {};
  settings.hooks[HOOK_EVENT] ??= [];
  const groups = settings.hooks[HOOK_EVENT];

  for (const group of groups) {
    for (const hook of group.hooks) {
      if (hook.command.trim() === command.trim()) {
        return { changed: false, reason: "already-present" };
      }
    }
  }

  let target = groups.find((g) => (g.matcher ?? "") === "");
  if (!target) {
    target = { matcher: "", hooks: [] };
    groups.push(target);
  }
  target.hooks.push({ type: "command", command });
  return { changed: true, reason: "added" };
}

export function applyUninstall(settings: ClaudeSettings): PatchResult {
  const groups = settings.hooks?.[HOOK_EVENT];
  if (!groups || groups.length === 0) return { changed: false, reason: "not-present" };

  let removed = false;
  for (const group of groups) {
    const before = group.hooks.length;
    group.hooks = group.hooks.filter((h) => !isOurHookCommand(h.command));
    if (group.hooks.length !== before) removed = true;
  }

  settings.hooks![HOOK_EVENT] = groups.filter((g) => g.hooks.length > 0);
  if (settings.hooks![HOOK_EVENT].length === 0) {
    delete settings.hooks![HOOK_EVENT];
  }
  if (settings.hooks && Object.keys(settings.hooks).length === 0) {
    delete settings.hooks;
  }

  return removed ? { changed: true, reason: "removed" } : { changed: false, reason: "not-present" };
}