package handler

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"mime"
	"mime/multipart"
	"net/http"
	"strings"

	"github.com/basketikun/infinite-canvas/service"
)

func AIImagesGenerations(w http.ResponseWriter, r *http.Request) {
	proxyAIRequest(w, r, "/images/generations")
}

func AIImagesEdits(w http.ResponseWriter, r *http.Request) {
	proxyAIRequest(w, r, "/images/edits")
}

func AIChatCompletions(w http.ResponseWriter, r *http.Request) {
	proxyAIRequest(w, r, "/chat/completions")
}

func AIVideos(w http.ResponseWriter, r *http.Request) {
	proxyAIRequest(w, r, "/videos")
}

func AIVideo(w http.ResponseWriter, r *http.Request, id string) {
	proxyAIGetRequest(w, r, "/videos/"+id)
}

func AIVideoContent(w http.ResponseWriter, r *http.Request, id string) {
	proxyAIGetRequest(w, r, "/videos/"+id+"/content")
}

func proxyAIGetRequest(w http.ResponseWriter, r *http.Request, path string) {
	modelName := r.URL.Query().Get("model")
	if strings.TrimSpace(modelName) == "" {
		modelName = "sora-2"
	}
	channel, err := service.SelectModelChannel(modelName)
	if err != nil {
		log.Printf("AI proxy select channel failed: model=%s err=%v", modelName, err)
		Fail(w, "AI 接口请求失败")
		return
	}
	request, err := http.NewRequest(http.MethodGet, service.BuildModelChannelURL(channel, path), nil)
	if err != nil {
		Fail(w, "AI 接口请求失败")
		return
	}
	request.Header.Set("Authorization", "Bearer "+channel.APIKey)
	copyAIResponse(w, request, nil)
}

func proxyAIRequest(w http.ResponseWriter, r *http.Request, path string) {
	body, contentType, modelName, err := readAIRequest(r)
	if err != nil {
		log.Printf("AI proxy request read failed: %v", err)
		Fail(w, "AI 接口请求失败")
		return
	}
	user, ok := service.UserFromContext(r.Context())
	if !ok {
		Fail(w, "未登录或权限不足")
		return
	}
	credits, err := service.ModelCost(modelName)
	if err != nil {
		log.Printf("AI proxy read model cost failed: model=%s err=%v", modelName, err)
		Fail(w, "AI 接口请求失败")
		return
	}
	credits *= readAIRequestCount(body, contentType)
	channel, err := service.SelectModelChannel(modelName)
	if err != nil {
		log.Printf("AI proxy select channel failed: model=%s err=%v", modelName, err)
		Fail(w, "AI 接口请求失败")
		return
	}
	request, err := http.NewRequest(http.MethodPost, service.BuildModelChannelURL(channel, path), bytes.NewReader(body))
	if err != nil {
		log.Printf("AI proxy build request failed: url=%s err=%v", service.BuildModelChannelURL(channel, path), err)
		Fail(w, "AI 接口请求失败")
		return
	}
	request.Header.Set("Authorization", "Bearer "+channel.APIKey)
	if contentType != "" {
		request.Header.Set("Content-Type", contentType)
	}
	if err := service.ConsumeUserCredits(user.ID, modelName, credits, path); err != nil {
		FailError(w, err)
		return
	}
	copyAIResponse(w, request, func() {
		if err := service.RefundUserCredits(user.ID, modelName, credits, path); err != nil {
			log.Printf("AI proxy refund credits failed: user=%s model=%s credits=%d err=%v", user.ID, modelName, credits, err)
		}
	})
}

func copyAIResponse(w http.ResponseWriter, request *http.Request, onFailure func()) {
	response, err := http.DefaultClient.Do(request)
	if err != nil {
		log.Printf("AI proxy request failed: url=%s err=%v", request.URL.String(), err)
		if onFailure != nil {
			onFailure()
		}
		Fail(w, "AI 接口请求失败")
		return
	}
	defer response.Body.Close()

	if response.StatusCode >= http.StatusBadRequest {
		payload, _ := io.ReadAll(io.LimitReader(response.Body, 4096))
		log.Printf("AI upstream error: url=%s status=%d body=%s", request.URL.String(), response.StatusCode, strings.TrimSpace(string(payload)))
		if onFailure != nil {
			onFailure()
		}
		Fail(w, "AI 接口请求失败")
		return
	}

	for key, values := range response.Header {
		if strings.EqualFold(key, "Content-Length") {
			continue
		}
		for _, value := range values {
			w.Header().Add(key, value)
		}
	}
	w.WriteHeader(response.StatusCode)
	_, _ = io.Copy(w, response.Body)
}

func readAIRequest(r *http.Request) ([]byte, string, string, error) {
	contentType := r.Header.Get("Content-Type")
	body, err := io.ReadAll(r.Body)
	if err != nil {
		return nil, "", "", err
	}
	modelName := ""
	if strings.HasPrefix(contentType, "multipart/form-data") {
		modelName = readMultipartModel(body, contentType)
	} else {
		var payload struct {
			Model string `json:"model"`
		}
		_ = json.Unmarshal(body, &payload)
		modelName = payload.Model
	}
	if strings.TrimSpace(modelName) == "" {
		return nil, "", "", errMissingModel
	}
	return body, contentType, modelName, nil
}

func readMultipartModel(body []byte, contentType string) string {
	_, params, err := mime.ParseMediaType(contentType)
	if err != nil {
		return ""
	}
	reader := multipart.NewReader(bytes.NewReader(body), params["boundary"])
	form, err := reader.ReadForm(32 << 20)
	if err != nil {
		return ""
	}
	defer form.RemoveAll()
	if values := form.Value["model"]; len(values) > 0 {
		return values[0]
	}
	return ""
}

func readAIRequestCount(body []byte, contentType string) int {
	count := 1
	if strings.HasPrefix(contentType, "multipart/form-data") {
		_, params, err := mime.ParseMediaType(contentType)
		if err != nil {
			return count
		}
		form, err := multipart.NewReader(bytes.NewReader(body), params["boundary"]).ReadForm(32 << 20)
		if err != nil {
			return count
		}
		defer form.RemoveAll()
		if values := form.Value["n"]; len(values) > 0 {
			_, _ = fmt.Sscan(values[0], &count)
		}
	} else {
		var payload struct {
			N int `json:"n"`
		}
		_ = json.Unmarshal(body, &payload)
		count = payload.N
	}
	if count < 1 {
		return 1
	}
	return count
}

var errMissingModel = &aiError{"缺少模型名称"}

type aiError struct {
	message string
}

func (err *aiError) Error() string {
	return err.message
}