/**
 * arcrun component loader
 *
 * 解析優先序：
 *
 * 1. 內建零件（BUILTIN_COMPONENTS）— 純 JS，最快
 * 2. 外部 URL（https://...）— 直接 fetch，n8n/MCP/任何 HTTP 服務
 * 3. cmp_xxxxxxxx hash → 查 registry KV idx → canonical_id → 邏輯 Worker
 * 4. rec_xxxxxxxx hash → 查 RECIPES KV idx → canonical_id → KV recipe 執行
 * 5. 邏輯零件 canonical_id → Service Binding（同帳號不走公網）
 * 6. KV recipe canonical_id → 從 RECIPES KV 讀取 recipe → fetch 外部 API
 * 7. 內建 API recipe（gmail/telegram/gsheets 等，寫死的 fallback）
 * 8. 找不到 → 報錯
 */

import { BUILTIN_COMPONENTS } from './constants';
import { isComponentHash, isRecipeHash } from './hash';
import { resolveRecipe } from '../routes/recipes';
import type { Bindings, ComponentRunner, ServiceBinding } from '../types';

/** 邏輯零件 canonical_id → Service Binding key */
const LOGIC_BINDING_MAP: Record<string, keyof Bindings> = {
  if_control:           'SVC_IF_CONTROL',
  switch:               'SVC_SWITCH',
  foreach_control:      'SVC_FOREACH_CONTROL',
  filter:               'SVC_FILTER',
  merge:                'SVC_MERGE',
  try_catch:            'SVC_TRY_CATCH',
  wait:                 'SVC_WAIT',
  set:                  'SVC_SET',
  array_ops:            'SVC_ARRAY_OPS',
  string_ops:           'SVC_STRING_OPS',
  number_ops:           'SVC_NUMBER_OPS',
  date_ops:             'SVC_DATE_OPS',
  validate_json:        'SVC_VALIDATE_JSON',
  ai_transform_compile: 'SVC_AI_TRANSFORM_COMPILE',
  ai_transform_run:     'SVC_AI_TRANSFORM_RUN',
};

export function createComponentLoader(env: Bindings) {
  return async (componentId: string): Promise<ComponentRunner> => {

    // 1. 內建零件（純 JS，最優先）
    const builtin = BUILTIN_COMPONENTS.get(componentId);
    if (builtin) return builtin;

    // 2. 外部 URL
    if (componentId.startsWith('http://') || componentId.startsWith('https://')) {
      return makeHttpRunner(componentId);
    }

    // 3. cmp_hash → 查 WEBHOOKS KV idx → canonical_id → 邏輯 Worker
    if (isComponentHash(componentId)) {
      const canonicalId = await env.WEBHOOKS.get(`idx:${componentId}`);
      if (canonicalId) {
        return makeLogicRunner(canonicalId, env);
      }
      throw new Error(`找不到零件 hash "${componentId}"，請確認已透過 acr push 上傳`);
    }

    // 4. rec_hash → 查 RECIPES KV idx → recipe 執行
    if (isRecipeHash(componentId)) {
      const recipe = await resolveRecipe(componentId, env.RECIPES);
      if (recipe) return makeRecipeRunner(recipe);
      throw new Error(`找不到 recipe hash "${componentId}"，請確認已透過 acr push 上傳`);
    }

    // 5. 邏輯零件 canonical_id → Service Binding
    const logicRunner = makeLogicRunner(componentId, env);
    if (logicRunner) return logicRunner;

    // 6. KV recipe（動態，用戶 push 的）
    const kvRecipe = await resolveRecipe(componentId, env.RECIPES);
    if (kvRecipe) return makeRecipeRunner(kvRecipe);

    // 7. 內建 API recipe（寫死的 fallback）
    const builtinRecipe = BUILTIN_API_RECIPES[componentId];
    if (builtinRecipe) return builtinRecipe;

    // 8. 找不到
    throw new Error(
      `找不到零件 "${componentId}"。\n` +
      `邏輯零件：${Object.keys(LOGIC_BINDING_MAP).join(', ')}\n` +
      `或傳入外部 URL（https://...）、recipe hash（rec_xxxxxxxx）、零件 hash（cmp_xxxxxxxx）`
    );
  };
}

// ── 執行器工廠 ────────────────────────────────────────────────────────────────

function makeHttpRunner(url: string): ComponentRunner {
  return async (ctx: unknown) => {
    const res = await fetch(url, {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify(ctx),
    });
    if (!res.ok) {
      const text = await res.text();
      return { success: false, status: res.status, error: text.slice(0, 200) };
    }
    try { return await res.json(); }
    catch { return { success: true, data: await res.text() }; }
  };
}

function makeLogicRunner(canonicalId: string, env: Bindings): ComponentRunner | null {
  const bindingKey = LOGIC_BINDING_MAP[canonicalId];
  if (!bindingKey) return null;

  const svc = env[bindingKey] as ServiceBinding | undefined;
  if (svc) {
    return async (ctx: unknown) => {
      const res = await svc.fetch(new Request('https://component/', {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify(ctx),
      }));
      if (!res.ok) {
        const text = await res.text();
        return { success: false, error: `${canonicalId} 回傳 ${res.status}: ${text.slice(0, 200)}` };
      }
      try { return await res.json(); }
      catch { return { success: false, error: `${canonicalId} 回傳非 JSON` }; }
    };
  }

  // Service Binding 未配置時 fallback 到公網（自製零件 or 開發環境）
  const fallbackUrl = `https://${canonicalId.replace(/_/g, '-')}.arcrun.dev`;
  return makeHttpRunner(fallbackUrl);
}

function makeRecipeRunner(recipe: import('../routes/recipes').RecipeDefinition): ComponentRunner {
  return async (ctx: unknown) => {
    const ctxObj = (ctx && typeof ctx === 'object') ? ctx as Record<string, unknown> : {};

    // 模板替換：把 {{key}} 換成 ctx 裡的值
    const interpolate = (s: string) =>
      s.replace(/\{\{(\w+)\}\}/g, (_, k) => String(ctxObj[k] ?? ''));

    const method = (recipe.method ?? 'POST').toUpperCase();
    const headers: Record<string, string> = { 'Content-Type': 'application/json' };
    for (const [k, v] of Object.entries(recipe.headers ?? {})) {
      headers[k] = interpolate(v);
    }

    // body：把 recipe.body 裡的 {{key}} 都換掉
    let bodyStr: string | undefined;
    if (recipe.body) {
      bodyStr = interpolate(JSON.stringify(recipe.body));
    } else if (method !== 'GET') {
      bodyStr = JSON.stringify(ctxObj);
    }

    const res = await fetch(interpolate(recipe.endpoint), {
      method,
      headers,
      body: bodyStr,
    });

    const data = await res.json().catch(() => res.text());
    return { success: res.ok, status: res.status, data };
  };
}

// ── 內建 API recipe（不存在 KV，直接寫死）────────────────────────────────────

const BUILTIN_API_RECIPES: Record<string, ComponentRunner> = {
  http_request: async (ctx) => {
    const c = ctx as Record<string, unknown>;
    const url = c.url as string;
    if (!url) return { success: false, error: 'url 必填' };
    const method = ((c.method as string) ?? 'GET').toUpperCase();
    const headers = (c.headers as Record<string, string>) ?? {};
    const body = c.body !== undefined ? JSON.stringify(c.body) : undefined;
    const res = await fetch(url, { method, headers, body });
    const text = await res.text();
    let data: unknown = text;
    try { data = JSON.parse(text); } catch { /* keep as text */ }
    return { success: res.ok, status: res.status, data };
  },

  gmail: async (ctx) => {
    const c = ctx as Record<string, string>;
    if (!c.access_token) return { success: false, error: 'access_token 必填（由 credentials 注入）' };
    if (!c.to || !c.subject || !c.body) return { success: false, error: 'to, subject, body 必填' };
    const message = `To: ${c.to}\r\nSubject: ${c.subject}\r\nContent-Type: text/plain; charset=utf-8\r\n\r\n${c.body}`;
    const encoded = btoa(unescape(encodeURIComponent(message)))
      .replace(/\+/g, '-').replace(/\//g, '_').replace(/=+$/, '');
    const res = await fetch('https://gmail.googleapis.com/gmail/v1/users/me/messages/send', {
      method: 'POST',
      headers: { 'Authorization': `Bearer ${c.access_token}`, 'Content-Type': 'application/json' },
      body: JSON.stringify({ raw: encoded }),
    });
    return { success: res.ok, data: await res.json() };
  },

  telegram: async (ctx) => {
    const c = ctx as Record<string, string>;
    if (!c.bot_token) return { success: false, error: 'bot_token 必填（由 credentials 注入）' };
    const res = await fetch(`https://api.telegram.org/bot${c.bot_token}/sendMessage`, {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify({ chat_id: c.chat_id, text: c.text }),
    });
    return { success: res.ok, data: await res.json() };
  },

  line_notify: async (ctx) => {
    const c = ctx as Record<string, string>;
    if (!c.token) return { success: false, error: 'token 必填（由 credentials 注入）' };
    const res = await fetch('https://notify-api.line.me/api/notify', {
      method: 'POST',
      headers: { 'Authorization': `Bearer ${c.token}`, 'Content-Type': 'application/x-www-form-urlencoded' },
      body: new URLSearchParams({ message: c.message }).toString(),
    });
    return { success: res.ok, data: await res.json() };
  },

  google_sheets: async (ctx) => {
    const c = ctx as Record<string, unknown>;
    if (!c.access_token) return { success: false, error: 'access_token 必填（由 credentials 注入）' };
    const hdrs = { 'Authorization': `Bearer ${c.access_token}`, 'Content-Type': 'application/json' };
    if ((c.operation ?? 'read') === 'read') {
      const res = await fetch(
        `https://sheets.googleapis.com/v4/spreadsheets/${c.spreadsheet_id}/values/${c.range}`,
        { headers: hdrs }
      );
      return { success: res.ok, data: await res.json() };
    }
    const res = await fetch(
      `https://sheets.googleapis.com/v4/spreadsheets/${c.spreadsheet_id}/values/${c.range}:append?valueInputOption=USER_ENTERED`,
      { method: 'POST', headers: hdrs, body: JSON.stringify({ values: c.values }) }
    );
    return { success: res.ok, data: await res.json() };
  },

  cron: async (ctx) => ({ success: true, data: ctx }),
};