package providers

import (
	"bufio"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"strings"

	"gophergate/internal/config"
	"gophergate/internal/models"
	"github.com/go-resty/resty/v2"
)

type DeepSeekProvider struct {
	client *resty.Client
	config config.DeepSeekConfig
	apiKey string
}

func NewDeepSeekProvider(cfg config.DeepSeekConfig, apiKey string) *DeepSeekProvider {
	return &DeepSeekProvider{
		client: resty.New(),
		config: cfg,
		apiKey: apiKey,
	}
}

func (p *DeepSeekProvider) Name() string {
	return "deepseek"
}

type deepSeekUsage struct {
	PromptTokens          uint32 `json:"prompt_tokens"`
	CompletionTokens      uint32 `json:"completion_tokens"`
	TotalTokens           uint32 `json:"total_tokens"`
	PromptCacheHitTokens  uint32 `json:"prompt_cache_hit_tokens"`
	PromptCacheMissTokens uint32 `json:"prompt_cache_miss_tokens"`
	CompletionTokensDetails *struct {
		ReasoningTokens uint32 `json:"reasoning_tokens"`
	} `json:"completion_tokens_details"`
}

func (u *deepSeekUsage) ToUnified() *models.Usage {
	usage := &models.Usage{
		PromptTokens:     u.PromptTokens,
		CompletionTokens: u.CompletionTokens,
		TotalTokens:      u.TotalTokens,
	}
	if u.PromptCacheHitTokens > 0 {
		usage.CacheReadTokens = &u.PromptCacheHitTokens
	}
	if u.PromptCacheMissTokens > 0 {
		usage.CacheWriteTokens = &u.PromptCacheMissTokens
	}
	if u.CompletionTokensDetails != nil && u.CompletionTokensDetails.ReasoningTokens > 0 {
		usage.ReasoningTokens = &u.CompletionTokensDetails.ReasoningTokens
	}
	return usage
}

func (p *DeepSeekProvider) ChatCompletion(ctx context.Context, req *models.UnifiedRequest) (*models.ChatCompletionResponse, error) {
	messagesJSON, err := MessagesToOpenAIJSON(req.Messages)
	if err != nil {
		return nil, fmt.Errorf("failed to convert messages: %w", err)
	}

	body := BuildOpenAIBody(req, messagesJSON, false)

	// Sanitize for deepseek-reasoner
	if req.Model == "deepseek-reasoner" {
		delete(body, "temperature")
		delete(body, "top_p")
		delete(body, "presence_penalty")
		delete(body, "frequency_penalty")
		
		if msgs, ok := body["messages"].([]interface{}); ok {
			for _, m := range msgs {
				if msg, ok := m.(map[string]interface{}); ok {
					if msg["role"] == "assistant" {
						if msg["reasoning_content"] == nil {
							msg["reasoning_content"] = " "
						}
						if msg["content"] == nil || msg["content"] == "" {
							msg["content"] = ""
						}
					}
				}
			}
		}
	}

	resp, err := p.client.R().
		SetContext(ctx).
		SetHeader("Authorization", "Bearer "+p.apiKey).
		SetBody(body).
		Post(fmt.Sprintf("%s/chat/completions", p.config.BaseURL))

	if err != nil {
		return nil, fmt.Errorf("request failed: %w", err)
	}

	if !resp.IsSuccess() {
		return nil, fmt.Errorf("DeepSeek API error (%d): %s", resp.StatusCode(), resp.String())
	}

	var respJSON map[string]interface{}
	if err := json.Unmarshal(resp.Body(), &respJSON); err != nil {
		return nil, fmt.Errorf("failed to parse response: %w", err)
	}

	result, err := ParseOpenAIResponse(respJSON, req.Model)
	if err != nil {
		return nil, err
	}

	// Fix usage for DeepSeek specifically if details were missing in ParseOpenAIResponse
	if usageData, ok := respJSON["usage"]; ok {
		var dUsage deepSeekUsage
		usageBytes, _ := json.Marshal(usageData)
		if err := json.Unmarshal(usageBytes, &dUsage); err == nil {
			result.Usage = dUsage.ToUnified()
		}
	}

	return result, nil
}

func (p *DeepSeekProvider) ChatCompletionStream(ctx context.Context, req *models.UnifiedRequest) (<-chan *models.ChatCompletionStreamResponse, error) {
	messagesJSON, err := MessagesToOpenAIJSON(req.Messages)
	if err != nil {
		return nil, fmt.Errorf("failed to convert messages: %w", err)
	}

	body := BuildOpenAIBody(req, messagesJSON, true)

	// Sanitize for deepseek-reasoner
	if req.Model == "deepseek-reasoner" {
		delete(body, "temperature")
		delete(body, "top_p")
		delete(body, "presence_penalty")
		delete(body, "frequency_penalty")
		
		if msgs, ok := body["messages"].([]interface{}); ok {
			for _, m := range msgs {
				if msg, ok := m.(map[string]interface{}); ok {
					if msg["role"] == "assistant" {
						if msg["reasoning_content"] == nil {
							msg["reasoning_content"] = " "
						}
						if msg["content"] == nil || msg["content"] == "" {
							msg["content"] = ""
						}
					}
				}
			}
		}
	}

	resp, err := p.client.R().
		SetContext(ctx).
		SetHeader("Authorization", "Bearer "+p.apiKey).
		SetBody(body).
		SetDoNotParseResponse(true).
		Post(fmt.Sprintf("%s/chat/completions", p.config.BaseURL))

	if err != nil {
		return nil, fmt.Errorf("request failed: %w", err)
	}

	if !resp.IsSuccess() {
		return nil, fmt.Errorf("DeepSeek API error (%d): %s", resp.StatusCode(), resp.String())
	}

	ch := make(chan *models.ChatCompletionStreamResponse)
	
	go func() {
		defer close(ch)
		// Custom scanner loop to handle DeepSeek specific usage in chunks
		err := StreamDeepSeek(resp.RawBody(), ch)
		if err != nil {
			fmt.Printf("DeepSeek Stream error: %v\n", err)
		}
	}()

	return ch, nil
}

func StreamDeepSeek(ctx io.ReadCloser, ch chan<- *models.ChatCompletionStreamResponse) error {
	defer ctx.Close()
	scanner := bufio.NewScanner(ctx)
	for scanner.Scan() {
		line := scanner.Text()
		if line == "" || !strings.HasPrefix(line, "data: ") {
			continue
		}

		data := strings.TrimPrefix(line, "data: ")
		if data == "[DONE]" {
			break
		}

		var chunk models.ChatCompletionStreamResponse
		if err := json.Unmarshal([]byte(data), &chunk); err != nil {
			continue
		}

		// Fix DeepSeek specific usage in stream
		var rawChunk struct {
			Usage *deepSeekUsage `json:"usage"`
		}
		if err := json.Unmarshal([]byte(data), &rawChunk); err == nil && rawChunk.Usage != nil {
			chunk.Usage = rawChunk.Usage.ToUnified()
		}

		ch <- &chunk
	}
	return scanner.Err()
}