package dx

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"strings"
	"time"
)

// HTTPStatusError preserves the telecom response body for non-200 responses.
// RespCode is the raw carrier error code when the gateway supplies one.
type HTTPStatusError struct {
	StatusCode int
	Body       string
	RespCode   string
}

func (e *HTTPStatusError) Error() string {
	if e == nil {
		return "telecom HTTP status error"
	}
	return fmt.Sprintf("http status %d: %s", e.StatusCode, e.Body)
}

// Config 网关鉴权与请求配置
type Config struct {
	BaseURL       string // 默认 https://cmp-api.ctwing.cn:20164
	AppKey        string
	AppSecret     string
	Timeout       time.Duration
	UppercaseSign bool
}

// Client API 客户端
type Client struct {
	baseURL       string
	appKey        string
	appSecret     string
	http          *http.Client
	uppercaseSign bool
}

// New 创建客户端
func NewClient(cfg Config) *Client {
	base := cfg.BaseURL
	if base == "" {
		base = DefaultBaseURL
	}
	timeout := cfg.Timeout
	if timeout <= 0 {
		timeout = 10 * time.Second
	}
	return &Client{
		baseURL:       strings.TrimSuffix(base, "/"),
		appKey:        cfg.AppKey,
		appSecret:     cfg.AppSecret,
		uppercaseSign: cfg.UppercaseSign,
		http: &http.Client{
			Timeout: timeout,
		},
	}
}

// DoGetRequest 通用GET请求（自动处理签名）
// endpoint: API路径，如 "/api/v1/openbill/queryTraffic"
// params: 查询参数，需调用方自行构建
func (c *Client) DoGetRequest(ctx context.Context, endpoint string, params url.Values) ([]byte, error) {
	req, err := c.doGetRequest(ctx, endpoint, params)
	if err != nil {
		return nil, err
	}
	return c.doRequest(req)
}

func (c *Client) DoPostJSONRequest(ctx context.Context, endpoint string, body []byte) ([]byte, error) {
	timestamp := GetTimestampGMT()
	signStr, err := BuildSign("", string(body), c.appSecret, timestamp)
	if c.uppercaseSign {
		signStr, err = BuildSignV3("", string(body), c.appSecret, timestamp)
	}
	if err != nil {
		return nil, err
	}
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, c.baseURL+endpoint, strings.NewReader(string(body)))
	if err != nil {
		return nil, err
	}
	req.Header.Set("AppKey", c.appKey)
	req.Header.Set("Sign", c.formatSign(signStr))
	req.Header.Set("Timestamp", timestamp)
	req.Header.Set("Content-Type", "application/json")
	return c.doRequest(req)
}

// doGetRequest 封装通用的 GET 请求构建逻辑
func (c *Client) doGetRequest(ctx context.Context, endpoint string, params url.Values) (*http.Request, error) {
	queryString := params.Encode()
	timestamp := GetTimestampGMT()
	signStr, err := BuildSign(queryString, "", c.appSecret, timestamp)
	if c.uppercaseSign {
		signStr, err = BuildSignV3(queryString, "", c.appSecret, timestamp)
	}
	if err != nil {
		return nil, err
	}
	reqURL := c.baseURL + endpoint + "?" + queryString
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, reqURL, nil)
	if err != nil {
		return nil, err
	}
	req.Header.Set("AppKey", c.appKey)
	req.Header.Set("Sign", c.formatSign(signStr))
	req.Header.Set("Timestamp", timestamp)
	return req, nil
}

func (c *Client) formatSign(sign string) string {
	if c.uppercaseSign {
		return strings.ToUpper(sign)
	}
	return sign
}

// doRequest 执行HTTP请求
func (c *Client) doRequest(req *http.Request) ([]byte, error) {
	resp, err := c.http.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, err
	}

	if resp.StatusCode != http.StatusOK {
		var errorBody struct {
			RespCode string `json:"respCode"`
		}
		_ = json.Unmarshal(body, &errorBody)
		if c.uppercaseSign && strings.TrimSpace(errorBody.RespCode) == "" {
			errorBody.RespCode = resp.Header.Get("gw-errorCode")
		}
		return nil, &HTTPStatusError{
			StatusCode: resp.StatusCode,
			Body:       string(body),
			RespCode:   strings.TrimSpace(errorBody.RespCode),
		}
	}
	return body, nil
}