// Package ost 调用科大讯飞 SparkChain SDK 里 RegionMSFT 那条录音文件转写。
//
// SDK 二进制里的引擎名是 iflyrec_voice_mul_cbm_msft_24h，走海外 OST：
// 创建 https://<host>/v2/ost/pro_create ，查询 https://<host>/v2/ost/query 。
// 音频不经过讯飞上传接口，直接用客户端已经放到 OSS 上的公网地址。
package ost

import (
	"bytes"
	"crypto/hmac"
	"crypto/sha256"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"strings"
	"time"

	"github.com/google/uuid"
)

const (
	defaultHost     = "ost-api-sg.xf-yun.com"
	defaultTaskType = "iflyrec_voice_mul_cbm_msft_24h"
	createPath      = "/v2/ost/create"
	queryPath       = "/v2/ost/query"
)

// Segment 一句转写。StartMs/EndMs 是相对音频开头的毫秒。
type Segment struct {
	Text    string
	StartMs int64
	EndMs   int64
	Speaker string
}

// Client 讯飞 OST 客户端。
type Client struct {
	AppID    string
	APIKey   string
	Secret   string
	Host     string
	TaskType string
	HTTP     *http.Client
}

// New 用 SparkChain 的 appId / apiKey / apiSecret 建客户端。
func New(appID, apiKey, secret, host, taskType string) (*Client, error) {
	if strings.TrimSpace(appID) == "" || strings.TrimSpace(apiKey) == "" || strings.TrimSpace(secret) == "" {
		return nil, fmt.Errorf("iflytek ost: app_id/api_key/api_secret 都不能空")
	}
	host = strings.TrimSpace(host)
	if host == "" {
		host = defaultHost
	}
	host = strings.TrimPrefix(strings.TrimPrefix(host, "https://"), "http://")
	host = strings.TrimRight(host, "/")
	taskType = strings.TrimSpace(taskType)
	if taskType == "" {
		taskType = defaultTaskType
	}
	return &Client{
		AppID:    appID,
		APIKey:   apiKey,
		Secret:   secret,
		Host:     host,
		TaskType: taskType,
		HTTP:     &http.Client{Timeout: 45 * time.Second},
	}, nil
}

// Create 提交一条公网音频。language 用 BCP-47（zh-CN / en-US），空则按中文。
func (c *Client) Create(audioURL string, speaker bool, language string) (string, error) {
	enc, format := audioEncoding(audioURL)
	business := map[string]any{
		"request_id": strings.ReplaceAll(uuid.NewString(), "-", ""),
		"task_type":  c.TaskType,
		"language":   ostLanguage(language),
	}
	applySpeaker(business, c.TaskType, speaker, enc)
	body := map[string]any{
		"common":   map[string]string{"app_id": c.AppID},
		"business": business,
		"data": map[string]any{
			"audio_url": audioURL,
			"audio_src": "http",
			"format":    format,
			"encoding":  enc,
		},
	}
	var resp struct {
		Code    int    `json:"code"`
		Message string `json:"message"`
		Data    struct {
			TaskID string `json:"task_id"`
		} `json:"data"`
	}
	if err := c.post(createPath, body, &resp); err != nil {
		return "", err
	}
	if resp.Code != 0 {
		return "", fmt.Errorf("iflytek ost create: code=%d %s", resp.Code, resp.Message)
	}
	if resp.Data.TaskID == "" {
		return "", fmt.Errorf("iflytek ost create: 没有 task_id")
	}
	return resp.Data.TaskID, nil
}

// msftSpeakerCap 微软文件转写的说话人数上限。speaker_num 合法范围是 1–35，
// 不传时文档默认 1，等于所有人合成一个角色。会议人数事先不知道，按 10 交给引擎去分。
const msftSpeakerCap = 10

// applySpeaker 按引擎写角色分离参数。
// 微软通道（task_type 含 msft）认 spkdia，不认讯飞自研的 vspp_on。
// 自研通道的 mp3 官方写明不支持角色分离，硬开会失败。
func applySpeaker(business map[string]any, taskType string, speaker bool, enc string) {
	if !speaker {
		return
	}
	if strings.Contains(taskType, "msft") {
		business["spkdia"] = 1
		business["speaker_num"] = msftSpeakerCap
		return
	}
	if enc == "lame" {
		return
	}
	business["vspp_on"] = 1
	business["speaker_num"] = 0
}

// QueryStatus 任务状态。running 表示还要再查，failed 时 err 带原因。
type QueryStatus int

const (
	StatusRunning QueryStatus = iota
	StatusSuccess
	StatusFailed
)

// Query 查一次。完成时 segments 是按句切开的文本。
func (c *Client) Query(taskID string) (QueryStatus, []Segment, error) {
	body := map[string]any{
		"common":   map[string]string{"app_id": c.AppID},
		"business": map[string]string{"task_id": taskID},
	}
	var raw map[string]any
	if err := c.post(queryPath, body, &raw); err != nil {
		return StatusFailed, nil, err
	}
	code := intFrom(raw["code"])
	if code != 0 {
		return StatusFailed, nil, fmt.Errorf("iflytek ost query: code=%d %v", code, raw["message"])
	}
	data, _ := raw["data"].(map[string]any)
	if data == nil {
		return StatusRunning, nil, nil
	}
	switch fmt.Sprint(data["task_status"]) {
	case "1", "2", "":
		return StatusRunning, nil, nil
	case "3", "4":
		return StatusSuccess, parseLattice(data["result"]), nil
	default:
		return StatusFailed, nil, fmt.Errorf("iflytek ost query: task_status=%v %v", data["task_status"], raw["message"])
	}
}

func (c *Client) post(path string, payload any, out any) error {
	raw, err := json.Marshal(payload)
	if err != nil {
		return err
	}
	endpoint := "https://" + c.Host + path
	req, err := http.NewRequest(http.MethodPost, endpoint, bytes.NewReader(raw))
	if err != nil {
		return err
	}
	req.Host = c.Host
	for k, v := range c.authHeader(path, raw) {
		if k == "Host" {
			continue
		}
		req.Header.Set(k, v)
	}
	client := c.HTTP
	if client.CheckRedirect == nil {
		client.CheckRedirect = func(req *http.Request, via []*http.Request) error {
			return http.ErrUseLastResponse
		}
	}
	resp, err := client.Do(req)
	if err != nil {
		return fmt.Errorf("iflytek ost %s: %w", path, err)
	}
	defer resp.Body.Close()
	buf, err := io.ReadAll(io.LimitReader(resp.Body, 8<<20))
	if err != nil {
		return err
	}
	if resp.StatusCode != http.StatusOK {
		if json.Unmarshal(buf, out) == nil {
			return nil
		}
		return fmt.Errorf("iflytek ost %s: http %d %s", endpoint, resp.StatusCode, truncate(string(buf), 300))
	}
	if err := json.Unmarshal(buf, out); err != nil {
		return fmt.Errorf("iflytek ost %s: 响应不是 JSON: %s", path, truncate(string(buf), 200))
	}
	return nil
}

func (c *Client) authHeader(path string, body []byte) map[string]string {
	sum := sha256.Sum256(body)
	digest := "SHA-256=" + base64.StdEncoding.EncodeToString(sum[:])
	date := time.Now().UTC().Format("Mon, 02 Jan 2006 15:04:05 GMT")
	origin := "host: " + c.Host + "\n" +
		"date: " + date + "\n" +
		"POST " + path + " HTTP/1.1\n" +
		"digest: " + digest
	mac := hmac.New(sha256.New, []byte(c.Secret))
	_, _ = mac.Write([]byte(origin))
	signature := base64.StdEncoding.EncodeToString(mac.Sum(nil))
	auth := fmt.Sprintf(`api_key="%s", algorithm="hmac-sha256", headers="host date request-line digest", signature="%s"`,
		c.APIKey, signature)
	return map[string]string{
		"Content-Type":  "application/json",
		"Accept":        "application/json",
		"Host":          c.Host,
		"Date":          date,
		"Digest":        digest,
		"Authorization": auth,
	}
}

func ostLanguage(code string) string {
	c := strings.TrimSpace(code)
	if c == "" {
		return "zh-CN"
	}
	c = strings.ReplaceAll(c, "_", "-")
	if !strings.Contains(c, "-") {
		switch strings.ToLower(c) {
		case "zh":
			return "zh-CN"
		case "en":
			return "en-US"
		case "ja":
			return "ja-JP"
		case "ko":
			return "ko-KR"
		}
	}
	return c
}

func audioEncoding(audioURL string) (encoding, format string) {
	u, err := url.Parse(audioURL)
	path := audioURL
	if err == nil && u.Path != "" {
		path = u.Path
	}
	lower := strings.ToLower(path)
	switch {
	case strings.HasSuffix(lower, ".mp3"):
		return "lame", "audio/mpeg"
	case strings.HasSuffix(lower, ".wav"), strings.HasSuffix(lower, ".pcm"):
		return "raw", "audio/L16;rate=16000"
	default:
		return "raw", "audio/L16;rate=16000"
	}
}

// parseLattice 把 OST 的 lattice 收成一句一条。json_1best 有时是对象，有时是字符串。
func parseLattice(result any) []Segment {
	obj, _ := result.(map[string]any)
	if obj == nil {
		if s, ok := result.(string); ok && s != "" {
			_ = json.Unmarshal([]byte(s), &obj)
		}
	}
	if obj == nil {
		return nil
	}
	lattice, _ := obj["lattice"].([]any)
	if len(lattice) == 0 {
		lattice, _ = obj["lattice2"].([]any)
	}
	out := make([]Segment, 0, len(lattice))
	for _, item := range lattice {
		m, _ := item.(map[string]any)
		if m == nil {
			continue
		}
		best := unwrapBest(m["json_1best"])
		st, _ := best["st"].(map[string]any)
		if st == nil {
			continue
		}
		text := wordsOf(st)
		if text == "" {
			continue
		}
		spk := strings.TrimSpace(fmt.Sprint(m["spk"]))
		if spk == "" || spk == "<nil>" {
			spk = strings.TrimSpace(fmt.Sprint(st["rl"]))
		}
		out = append(out, Segment{
			Text:    text,
			StartMs: intFrom(st["bg"]),
			EndMs:   intFrom(st["ed"]),
			Speaker: spk,
		})
	}
	return out
}

func unwrapBest(v any) map[string]any {
	switch t := v.(type) {
	case map[string]any:
		return t
	case string:
		var m map[string]any
		if json.Unmarshal([]byte(t), &m) == nil {
			return m
		}
	}
	return map[string]any{}
}

func wordsOf(st map[string]any) string {
	rts, _ := st["rt"].([]any)
	var b strings.Builder
	for _, rt := range rts {
		rtm, _ := rt.(map[string]any)
		wss, _ := rtm["ws"].([]any)
		for _, ws := range wss {
			wsm, _ := ws.(map[string]any)
			cws, _ := wsm["cw"].([]any)
			for _, cw := range cws {
				cwm, _ := cw.(map[string]any)
				if fmt.Sprint(cwm["wp"]) == "g" {
					continue
				}
				w, _ := cwm["w"].(string)
				b.WriteString(w)
			}
		}
	}
	return strings.TrimSpace(b.String())
}

func intFrom(v any) int64 {
	switch t := v.(type) {
	case float64:
		return int64(t)
	case json.Number:
		n, _ := t.Int64()
		return n
	case string:
		var n int64
		fmt.Sscan(t, &n)
		return n
	case int:
		return int64(t)
	case int64:
		return t
	default:
		return 0
	}
}

func truncate(s string, n int) string {
	if len(s) <= n {
		return s
	}
	return s[:n]
}