package client

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

	"cursor/internal/logger"
	"cursor/internal/modelchannel"
	"cursor/internal/netproxy"
)

// RemoteModel 表示从模型服务 /models 端点拉取到的一个模型。
type RemoteModel struct {
	ID string `json:"id"`
}

// RemoteModelsResult 表示一次模型列表拉取结果。
type RemoteModelsResult struct {
	Models []RemoteModel `json:"models"`
}

const remoteModelsFetchTimeout = 30 * time.Second

// ListRemoteModels 通过 openai/anthropic 兼容的 /v1/models 端点拉取模型列表。
func (s *ProxyService) ListRemoteModels(adapterType string, baseURL string, apiKey string) (RemoteModelsResult, error) {
	result := RemoteModelsResult{Models: []RemoteModel{}}
	if s == nil {
		return result, fmt.Errorf("服务未初始化")
	}
	adapterType = strings.ToLower(strings.TrimSpace(adapterType))
	baseURL = strings.TrimSpace(baseURL)
	apiKey = strings.TrimSpace(apiKey)
	logger.RegisterSecrets(apiKey)
	if adapterType != "openai" && adapterType != "anthropic" {
		return result, fmt.Errorf("模型类型仅支持 openai 或 anthropic")
	}
	if baseURL == "" {
		return result, fmt.Errorf("接口地址不能为空")
	}
	if apiKey == "" {
		return result, fmt.Errorf("访问密钥不能为空")
	}
	normalizedBaseURL, err := modelchannel.NormalizeBaseURL(baseURL)
	if err != nil {
		return result, err
	}

	endpoint := buildModelsEndpoint(adapterType, normalizedBaseURL)
	ctx, cancel := context.WithTimeout(context.Background(), remoteModelsFetchTimeout)
	defer cancel()

	request, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, nil)
	if err != nil {
		return result, fmt.Errorf("构建模型列表请求失败: %w", err)
	}
	if adapterType == "openai" {
		request.Header.Set("Authorization", "Bearer "+apiKey)
	} else {
		request.Header.Set("x-api-key", apiKey)
		request.Header.Set("anthropic-version", "2023-06-01")
	}
	request.Header.Set("Accept", "application/json")

	response, err := netproxy.CredentialSafeClient(http.DefaultClient).Do(request)
	if err != nil {
		return result, fmt.Errorf("请求模型列表失败: %w", err)
	}
	defer response.Body.Close()

	body, err := io.ReadAll(io.LimitReader(response.Body, 8<<20))
	if err != nil {
		return result, fmt.Errorf("读取模型列表响应失败: %w", err)
	}
	if response.StatusCode < 200 || response.StatusCode >= 300 {
		return result, fmt.Errorf("模型列表接口返回 %d: %s", response.StatusCode, strings.TrimSpace(string(body)))
	}

	models, err := decodeRemoteModels(adapterType, body)
	if err != nil {
		return result, err
	}
	result.Models = models
	return result, nil
}

// buildModelsEndpoint 把规范化后的 baseURL 解析为模型列表端点，
// 与聊天转发的 URL 解析保持同样的幂等口径：
//   - baseURL 以 /v1 结尾：仅追加 /models，避免拼出 /v1/v1/models
//   - openai baseURL 内嵌完整聊天端点（/v1/responses、/v1/chat/completions）：仅剥离方法段，端点回退为 /v1/models
//   - 其余情况（裸 host、官方 anthropic 地址）：追加 /v1/models
func buildModelsEndpoint(adapterType string, normalizedBaseURL string) string {
	base := strings.TrimRight(normalizedBaseURL, "/")
	lower := strings.ToLower(base)
	if adapterType == "openai" {
		for _, endpoint := range []string{modelchannel.OpenAIEndpointChatCompletions, modelchannel.OpenAIEndpointResponses} {
			methodPath := strings.TrimPrefix(strings.ToLower(endpoint), "/v1")
			if methodPath != "" && strings.HasSuffix(lower, methodPath) {
				return base[:len(base)-len(methodPath)] + "/models"
			}
		}
	}
	if strings.HasSuffix(lower, "/v1") {
		return base + "/models"
	}
	return base + "/v1/models"
}

func decodeRemoteModels(adapterType string, body []byte) ([]RemoteModel, error) {
	var payload struct {
		Data []struct {
			ID string `json:"id"`
		} `json:"data"`
	}
	if err := json.Unmarshal(body, &payload); err != nil {
		return nil, fmt.Errorf("解析模型列表响应失败: %w", err)
	}
	seen := make(map[string]struct{}, len(payload.Data))
	models := make([]RemoteModel, 0, len(payload.Data))
	for _, item := range payload.Data {
		id := strings.TrimSpace(item.ID)
		if id == "" {
			continue
		}
		if _, exists := seen[id]; exists {
			continue
		}
		seen[id] = struct{}{}
		models = append(models, RemoteModel{ID: id})
	}
	if len(models) == 0 {
		return nil, fmt.Errorf("模型列表为空，请检查接口地址与密钥")
	}
	return models, nil
}