// Package openai provides HTTP handlers for OpenAI API endpoints.
// This package implements the OpenAI-compatible API interface, including model listing
// and chat completion functionality. It supports both streaming and non-streaming responses,
// and manages a pool of clients to interact with backend services.
// The handlers translate OpenAI API requests to the appropriate backend format and
// convert responses back to OpenAI-compatible format.
package openai

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

	"github.com/gin-gonic/gin"
	"github.com/luispater/CLIProxyAPI/internal/api/handlers"
	. "github.com/luispater/CLIProxyAPI/internal/constant"
	"github.com/luispater/CLIProxyAPI/internal/interfaces"
	"github.com/luispater/CLIProxyAPI/internal/registry"
	log "github.com/sirupsen/logrus"
	"github.com/tidwall/gjson"
	"github.com/tidwall/sjson"
)

// OpenAIAPIHandler contains the handlers for OpenAI API endpoints.
// It holds a pool of clients to interact with the backend service.
type OpenAIAPIHandler struct {
	*handlers.BaseAPIHandler
}

// NewOpenAIAPIHandler creates a new OpenAI API handlers instance.
// It takes an BaseAPIHandler instance as input and returns an OpenAIAPIHandler.
//
// Parameters:
//   - apiHandlers: The base API handlers instance
//
// Returns:
//   - *OpenAIAPIHandler: A new OpenAI API handlers instance
func NewOpenAIAPIHandler(apiHandlers *handlers.BaseAPIHandler) *OpenAIAPIHandler {
	return &OpenAIAPIHandler{
		BaseAPIHandler: apiHandlers,
	}
}

// HandlerType returns the identifier for this handler implementation.
func (h *OpenAIAPIHandler) HandlerType() string {
	return OPENAI
}

// Models returns the OpenAI-compatible model metadata supported by this handler.
func (h *OpenAIAPIHandler) Models() []map[string]any {
	// Get dynamic models from the global registry
	modelRegistry := registry.GetGlobalRegistry()
	return modelRegistry.GetAvailableModels("openai")
}

// OpenAIModels handles the /v1/models endpoint.
// It returns a list of available AI models with their capabilities
// and specifications in OpenAI-compatible format.
func (h *OpenAIAPIHandler) OpenAIModels(c *gin.Context) {
	c.JSON(http.StatusOK, gin.H{
		"object": "list",
		"data":   h.Models(),
	})
}

// ChatCompletions handles the /v1/chat/completions endpoint.
// It determines whether the request is for a streaming or non-streaming response
// and calls the appropriate handler based on the model provider.
//
// Parameters:
//   - c: The Gin context containing the HTTP request and response
func (h *OpenAIAPIHandler) ChatCompletions(c *gin.Context) {
	rawJSON, err := c.GetRawData()
	// If data retrieval fails, return a 400 Bad Request error.
	if err != nil {
		c.JSON(http.StatusBadRequest, handlers.ErrorResponse{
			Error: handlers.ErrorDetail{
				Message: fmt.Sprintf("Invalid request: %v", err),
				Type:    "invalid_request_error",
			},
		})
		return
	}

	// Check if the client requested a streaming response.
	streamResult := gjson.GetBytes(rawJSON, "stream")
	if streamResult.Type == gjson.True {
		h.handleStreamingResponse(c, rawJSON)
	} else {
		h.handleNonStreamingResponse(c, rawJSON)
	}

}

// Completions handles the /v1/completions endpoint.
// It determines whether the request is for a streaming or non-streaming response
// and calls the appropriate handler based on the model provider.
// This endpoint follows the OpenAI completions API specification.
//
// Parameters:
//   - c: The Gin context containing the HTTP request and response
func (h *OpenAIAPIHandler) Completions(c *gin.Context) {
	rawJSON, err := c.GetRawData()
	// If data retrieval fails, return a 400 Bad Request error.
	if err != nil {
		c.JSON(http.StatusBadRequest, handlers.ErrorResponse{
			Error: handlers.ErrorDetail{
				Message: fmt.Sprintf("Invalid request: %v", err),
				Type:    "invalid_request_error",
			},
		})
		return
	}

	// Check if the client requested a streaming response.
	streamResult := gjson.GetBytes(rawJSON, "stream")
	if streamResult.Type == gjson.True {
		h.handleCompletionsStreamingResponse(c, rawJSON)
	} else {
		h.handleCompletionsNonStreamingResponse(c, rawJSON)
	}

}

// convertCompletionsRequestToChatCompletions converts OpenAI completions API request to chat completions format.
// This allows the completions endpoint to use the existing chat completions infrastructure.
//
// Parameters:
//   - rawJSON: The raw JSON bytes of the completions request
//
// Returns:
//   - []byte: The converted chat completions request
func convertCompletionsRequestToChatCompletions(rawJSON []byte) []byte {
	root := gjson.ParseBytes(rawJSON)

	// Extract prompt from completions request
	prompt := root.Get("prompt").String()
	if prompt == "" {
		prompt = "Complete this:"
	}

	// Create chat completions structure
	out := `{"model":"","messages":[{"role":"user","content":""}]}`

	// Set model
	if model := root.Get("model"); model.Exists() {
		out, _ = sjson.Set(out, "model", model.String())
	}

	// Set the prompt as user message content
	out, _ = sjson.Set(out, "messages.0.content", prompt)

	// Copy other parameters from completions to chat completions
	if maxTokens := root.Get("max_tokens"); maxTokens.Exists() {
		out, _ = sjson.Set(out, "max_tokens", maxTokens.Int())
	}

	if temperature := root.Get("temperature"); temperature.Exists() {
		out, _ = sjson.Set(out, "temperature", temperature.Float())
	}

	if topP := root.Get("top_p"); topP.Exists() {
		out, _ = sjson.Set(out, "top_p", topP.Float())
	}

	if frequencyPenalty := root.Get("frequency_penalty"); frequencyPenalty.Exists() {
		out, _ = sjson.Set(out, "frequency_penalty", frequencyPenalty.Float())
	}

	if presencePenalty := root.Get("presence_penalty"); presencePenalty.Exists() {
		out, _ = sjson.Set(out, "presence_penalty", presencePenalty.Float())
	}

	if stop := root.Get("stop"); stop.Exists() {
		out, _ = sjson.SetRaw(out, "stop", stop.Raw)
	}

	if stream := root.Get("stream"); stream.Exists() {
		out, _ = sjson.Set(out, "stream", stream.Bool())
	}

	if logprobs := root.Get("logprobs"); logprobs.Exists() {
		out, _ = sjson.Set(out, "logprobs", logprobs.Bool())
	}

	if topLogprobs := root.Get("top_logprobs"); topLogprobs.Exists() {
		out, _ = sjson.Set(out, "top_logprobs", topLogprobs.Int())
	}

	if echo := root.Get("echo"); echo.Exists() {
		out, _ = sjson.Set(out, "echo", echo.Bool())
	}

	return []byte(out)
}

// convertChatCompletionsResponseToCompletions converts chat completions API response back to completions format.
// This ensures the completions endpoint returns data in the expected format.
//
// Parameters:
//   - rawJSON: The raw JSON bytes of the chat completions response
//
// Returns:
//   - []byte: The converted completions response
func convertChatCompletionsResponseToCompletions(rawJSON []byte) []byte {
	root := gjson.ParseBytes(rawJSON)

	// Base completions response structure
	out := `{"id":"","object":"text_completion","created":0,"model":"","choices":[]}`

	// Copy basic fields
	if id := root.Get("id"); id.Exists() {
		out, _ = sjson.Set(out, "id", id.String())
	}

	if created := root.Get("created"); created.Exists() {
		out, _ = sjson.Set(out, "created", created.Int())
	}

	if model := root.Get("model"); model.Exists() {
		out, _ = sjson.Set(out, "model", model.String())
	}

	if usage := root.Get("usage"); usage.Exists() {
		out, _ = sjson.SetRaw(out, "usage", usage.Raw)
	}

	// Convert choices from chat completions to completions format
	var choices []interface{}
	if chatChoices := root.Get("choices"); chatChoices.Exists() && chatChoices.IsArray() {
		chatChoices.ForEach(func(_, choice gjson.Result) bool {
			completionsChoice := map[string]interface{}{
				"index": choice.Get("index").Int(),
			}

			// Extract text content from message.content
			if message := choice.Get("message"); message.Exists() {
				if content := message.Get("content"); content.Exists() {
					completionsChoice["text"] = content.String()
				}
			} else if delta := choice.Get("delta"); delta.Exists() {
				// For streaming responses, use delta.content
				if content := delta.Get("content"); content.Exists() {
					completionsChoice["text"] = content.String()
				}
			}

			// Copy finish_reason
			if finishReason := choice.Get("finish_reason"); finishReason.Exists() {
				completionsChoice["finish_reason"] = finishReason.String()
			}

			// Copy logprobs if present
			if logprobs := choice.Get("logprobs"); logprobs.Exists() {
				completionsChoice["logprobs"] = logprobs.Value()
			}

			choices = append(choices, completionsChoice)
			return true
		})
	}

	if len(choices) > 0 {
		choicesJSON, _ := json.Marshal(choices)
		out, _ = sjson.SetRaw(out, "choices", string(choicesJSON))
	}

	return []byte(out)
}

// convertChatCompletionsStreamChunkToCompletions converts a streaming chat completions chunk to completions format.
// This handles the real-time conversion of streaming response chunks and filters out empty text responses.
//
// Parameters:
//   - chunkData: The raw JSON bytes of a single chat completions stream chunk
//
// Returns:
//   - []byte: The converted completions stream chunk, or nil if should be filtered out
func convertChatCompletionsStreamChunkToCompletions(chunkData []byte) []byte {
	root := gjson.ParseBytes(chunkData)

	// Check if this chunk has any meaningful content
	hasContent := false
	if chatChoices := root.Get("choices"); chatChoices.Exists() && chatChoices.IsArray() {
		chatChoices.ForEach(func(_, choice gjson.Result) bool {
			// Check if delta has content or finish_reason
			if delta := choice.Get("delta"); delta.Exists() {
				if content := delta.Get("content"); content.Exists() && content.String() != "" {
					hasContent = true
					return false // Break out of forEach
				}
			}
			// Also check for finish_reason to ensure we don't skip final chunks
			if finishReason := choice.Get("finish_reason"); finishReason.Exists() && finishReason.String() != "" && finishReason.String() != "null" {
				hasContent = true
				return false // Break out of forEach
			}
			return true
		})
	}

	// If no meaningful content, return nil to indicate this chunk should be skipped
	if !hasContent {
		return nil
	}

	// Base completions stream response structure
	out := `{"id":"","object":"text_completion","created":0,"model":"","choices":[]}`

	// Copy basic fields
	if id := root.Get("id"); id.Exists() {
		out, _ = sjson.Set(out, "id", id.String())
	}

	if created := root.Get("created"); created.Exists() {
		out, _ = sjson.Set(out, "created", created.Int())
	}

	if model := root.Get("model"); model.Exists() {
		out, _ = sjson.Set(out, "model", model.String())
	}

	// Convert choices from chat completions delta to completions format
	var choices []interface{}
	if chatChoices := root.Get("choices"); chatChoices.Exists() && chatChoices.IsArray() {
		chatChoices.ForEach(func(_, choice gjson.Result) bool {
			completionsChoice := map[string]interface{}{
				"index": choice.Get("index").Int(),
			}

			// Extract text content from delta.content
			if delta := choice.Get("delta"); delta.Exists() {
				if content := delta.Get("content"); content.Exists() && content.String() != "" {
					completionsChoice["text"] = content.String()
				} else {
					completionsChoice["text"] = ""
				}
			} else {
				completionsChoice["text"] = ""
			}

			// Copy finish_reason
			if finishReason := choice.Get("finish_reason"); finishReason.Exists() && finishReason.String() != "null" {
				completionsChoice["finish_reason"] = finishReason.String()
			}

			// Copy logprobs if present
			if logprobs := choice.Get("logprobs"); logprobs.Exists() {
				completionsChoice["logprobs"] = logprobs.Value()
			}

			choices = append(choices, completionsChoice)
			return true
		})
	}

	if len(choices) > 0 {
		choicesJSON, _ := json.Marshal(choices)
		out, _ = sjson.SetRaw(out, "choices", string(choicesJSON))
	}

	return []byte(out)
}

// handleNonStreamingResponse handles non-streaming chat completion responses
// for Gemini models. It selects a client from the pool, sends the request, and
// aggregates the response before sending it back to the client in OpenAI format.
//
// Parameters:
//   - c: The Gin context containing the HTTP request and response
//   - rawJSON: The raw JSON bytes of the OpenAI-compatible request
func (h *OpenAIAPIHandler) handleNonStreamingResponse(c *gin.Context, rawJSON []byte) {
	c.Header("Content-Type", "application/json")

	modelName := gjson.GetBytes(rawJSON, "model").String()
	cliCtx, cliCancel := h.GetContextWithCancel(h, c, context.Background())

	var cliClient interfaces.Client
	defer func() {
		if cliClient != nil {
			if mutex := cliClient.GetRequestMutex(); mutex != nil {
				mutex.Unlock()
			}
		}
	}()

	retryCount := 0
	for retryCount <= h.Cfg.RequestRetry {
		var errorResponse *interfaces.ErrorMessage
		cliClient, errorResponse = h.GetClient(modelName)
		if errorResponse != nil {
			c.Status(errorResponse.StatusCode)
			_, _ = fmt.Fprint(c.Writer, errorResponse.Error.Error())
			cliCancel()
			return
		}

		resp, err := cliClient.SendRawMessage(cliCtx, modelName, rawJSON, "")
		if err != nil {
			switch err.StatusCode {
			case 429:
				if h.Cfg.QuotaExceeded.SwitchProject {
					log.Debugf("quota exceeded, switch client")
					continue // Restart the client selection process
				}
			case 403, 408, 500, 502, 503, 504:
				log.Debugf("http status code %d, switch client", err.StatusCode)
				retryCount++
				continue
			default:
				// Forward other errors directly to the client
				c.Status(err.StatusCode)
				_, _ = c.Writer.Write([]byte(err.Error.Error()))
				cliCancel(err.Error)
			}
			break
		} else {
			_, _ = c.Writer.Write(resp)
			cliCancel(resp)
			break
		}
	}
}

// handleStreamingResponse handles streaming responses for Gemini models.
// It establishes a streaming connection with the backend service and forwards
// the response chunks to the client in real-time using Server-Sent Events.
//
// Parameters:
//   - c: The Gin context containing the HTTP request and response
//   - rawJSON: The raw JSON bytes of the OpenAI-compatible request
func (h *OpenAIAPIHandler) handleStreamingResponse(c *gin.Context, rawJSON []byte) {
	c.Header("Content-Type", "text/event-stream")
	c.Header("Cache-Control", "no-cache")
	c.Header("Connection", "keep-alive")
	c.Header("Access-Control-Allow-Origin", "*")

	// Get the http.Flusher interface to manually flush the response.
	flusher, ok := c.Writer.(http.Flusher)
	if !ok {
		c.JSON(http.StatusInternalServerError, handlers.ErrorResponse{
			Error: handlers.ErrorDetail{
				Message: "Streaming not supported",
				Type:    "server_error",
			},
		})
		return
	}

	modelName := gjson.GetBytes(rawJSON, "model").String()
	cliCtx, cliCancel := h.GetContextWithCancel(h, c, context.Background())

	var cliClient interfaces.Client
	defer func() {
		// Ensure the client's mutex is unlocked on function exit.
		if cliClient != nil {
			if mutex := cliClient.GetRequestMutex(); mutex != nil {
				mutex.Unlock()
			}
		}
	}()

	retryCount := 0
outLoop:
	for retryCount <= h.Cfg.RequestRetry {
		var errorResponse *interfaces.ErrorMessage
		cliClient, errorResponse = h.GetClient(modelName)
		if errorResponse != nil {
			c.Status(errorResponse.StatusCode)
			_, _ = fmt.Fprint(c.Writer, errorResponse.Error.Error())
			flusher.Flush()
			cliCancel()
			return
		}

		// Send the message and receive response chunks and errors via channels.
		respChan, errChan := cliClient.SendRawMessageStream(cliCtx, modelName, rawJSON, "")

		for {
			select {
			// Handle client disconnection.
			case <-c.Request.Context().Done():
				if c.Request.Context().Err().Error() == "context canceled" {
					log.Debugf("qwen client disconnected: %v", c.Request.Context().Err())
					cliCancel() // Cancel the backend request.
					return
				}
			// Process incoming response chunks.
			case chunk, okStream := <-respChan:
				if !okStream {
					// Stream is closed, send the final [DONE] message.
					_, _ = fmt.Fprintf(c.Writer, "data: [DONE]\n\n")
					flusher.Flush()
					cliCancel()
					return
				}

				_, _ = fmt.Fprintf(c.Writer, "data: %s\n\n", string(chunk))
				flusher.Flush()
			// Handle errors from the backend.
			case err, okError := <-errChan:
				if okError {
					switch err.StatusCode {
					case 429:
						if h.Cfg.QuotaExceeded.SwitchProject {
							log.Debugf("quota exceeded, switch client")
							continue outLoop // Restart the client selection process
						}
					case 403, 408, 500, 502, 503, 504:
						log.Debugf("http status code %d, switch client", err.StatusCode)
						retryCount++
						continue outLoop
					default:
						// Forward other errors directly to the client
						c.Status(err.StatusCode)
						_, _ = fmt.Fprint(c.Writer, err.Error.Error())
						flusher.Flush()
						cliCancel(err.Error)
					}
					return
				}
			// Send a keep-alive signal to the client.
			case <-time.After(500 * time.Millisecond):
			}
		}
	}
}

// handleCompletionsNonStreamingResponse handles non-streaming completions responses.
// It converts completions request to chat completions format, sends to backend,
// then converts the response back to completions format before sending to client.
//
// Parameters:
//   - c: The Gin context containing the HTTP request and response
//   - rawJSON: The raw JSON bytes of the OpenAI-compatible completions request
func (h *OpenAIAPIHandler) handleCompletionsNonStreamingResponse(c *gin.Context, rawJSON []byte) {
	c.Header("Content-Type", "application/json")

	// Convert completions request to chat completions format
	chatCompletionsJSON := convertCompletionsRequestToChatCompletions(rawJSON)

	modelName := gjson.GetBytes(chatCompletionsJSON, "model").String()
	cliCtx, cliCancel := h.GetContextWithCancel(h, c, context.Background())

	var cliClient interfaces.Client
	defer func() {
		if cliClient != nil {
			if mutex := cliClient.GetRequestMutex(); mutex != nil {
				mutex.Unlock()
			}
		}
	}()

	retryCount := 0
	for retryCount <= h.Cfg.RequestRetry {
		var errorResponse *interfaces.ErrorMessage
		cliClient, errorResponse = h.GetClient(modelName)
		if errorResponse != nil {
			c.Status(errorResponse.StatusCode)
			_, _ = fmt.Fprint(c.Writer, errorResponse.Error.Error())
			cliCancel()
			return
		}

		// Send the converted chat completions request
		resp, err := cliClient.SendRawMessage(cliCtx, modelName, chatCompletionsJSON, "")
		if err != nil {
			switch err.StatusCode {
			case 429:
				if h.Cfg.QuotaExceeded.SwitchProject {
					log.Debugf("quota exceeded, switch client")
					continue // Restart the client selection process
				}
			case 403, 408, 500, 502, 503, 504:
				log.Debugf("http status code %d, switch client", err.StatusCode)
				retryCount++
				continue
			default:
				// Forward other errors directly to the client
				c.Status(err.StatusCode)
				_, _ = c.Writer.Write([]byte(err.Error.Error()))
				cliCancel(err.Error)
			}
			break
		} else {
			// Convert chat completions response back to completions format
			completionsResp := convertChatCompletionsResponseToCompletions(resp)
			_, _ = c.Writer.Write(completionsResp)
			cliCancel(completionsResp)
			break
		}
	}
}

// handleCompletionsStreamingResponse handles streaming completions responses.
// It converts completions request to chat completions format, streams from backend,
// then converts each response chunk back to completions format before sending to client.
//
// Parameters:
//   - c: The Gin context containing the HTTP request and response
//   - rawJSON: The raw JSON bytes of the OpenAI-compatible completions request
func (h *OpenAIAPIHandler) handleCompletionsStreamingResponse(c *gin.Context, rawJSON []byte) {
	c.Header("Content-Type", "text/event-stream")
	c.Header("Cache-Control", "no-cache")
	c.Header("Connection", "keep-alive")
	c.Header("Access-Control-Allow-Origin", "*")

	// Get the http.Flusher interface to manually flush the response.
	flusher, ok := c.Writer.(http.Flusher)
	if !ok {
		c.JSON(http.StatusInternalServerError, handlers.ErrorResponse{
			Error: handlers.ErrorDetail{
				Message: "Streaming not supported",
				Type:    "server_error",
			},
		})
		return
	}

	// Convert completions request to chat completions format
	chatCompletionsJSON := convertCompletionsRequestToChatCompletions(rawJSON)

	modelName := gjson.GetBytes(chatCompletionsJSON, "model").String()
	cliCtx, cliCancel := h.GetContextWithCancel(h, c, context.Background())

	var cliClient interfaces.Client
	defer func() {
		// Ensure the client's mutex is unlocked on function exit.
		if cliClient != nil {
			if mutex := cliClient.GetRequestMutex(); mutex != nil {
				mutex.Unlock()
			}
		}
	}()

	retryCount := 0
outLoop:
	for retryCount <= h.Cfg.RequestRetry {
		var errorResponse *interfaces.ErrorMessage
		cliClient, errorResponse = h.GetClient(modelName)
		if errorResponse != nil {
			c.Status(errorResponse.StatusCode)
			_, _ = fmt.Fprint(c.Writer, errorResponse.Error.Error())
			flusher.Flush()
			cliCancel()
			return
		}

		// Send the converted chat completions request and receive response chunks
		respChan, errChan := cliClient.SendRawMessageStream(cliCtx, modelName, chatCompletionsJSON, "")

		for {
			select {
			// Handle client disconnection.
			case <-c.Request.Context().Done():
				if c.Request.Context().Err().Error() == "context canceled" {
					log.Debugf("client disconnected: %v", c.Request.Context().Err())
					cliCancel() // Cancel the backend request.
					return
				}
			// Process incoming response chunks.
			case chunk, okStream := <-respChan:
				if !okStream {
					// Stream is closed, send the final [DONE] message.
					_, _ = fmt.Fprintf(c.Writer, "data: [DONE]\n\n")
					flusher.Flush()
					cliCancel()
					return
				}

				// Convert chat completions chunk to completions chunk format
				completionsChunk := convertChatCompletionsStreamChunkToCompletions(chunk)
				// Skip this chunk if it has no meaningful content (empty text)
				if completionsChunk != nil {
					_, _ = fmt.Fprintf(c.Writer, "data: %s\n\n", string(completionsChunk))
					flusher.Flush()
				}
			// Handle errors from the backend.
			case err, okError := <-errChan:
				if okError {
					switch err.StatusCode {
					case 429:
						if h.Cfg.QuotaExceeded.SwitchProject {
							log.Debugf("quota exceeded, switch client")
							continue outLoop // Restart the client selection process
						}
					case 403, 408, 500, 502, 503, 504:
						log.Debugf("http status code %d, switch client", err.StatusCode)
						retryCount++
						continue outLoop
					default:
						// Forward other errors directly to the client
						c.Status(err.StatusCode)
						_, _ = fmt.Fprint(c.Writer, err.Error.Error())
						flusher.Flush()
						cliCancel(err.Error)
					}
					return
				}
			// Send a keep-alive signal to the client.
			case <-time.After(500 * time.Millisecond):
			}
		}
	}
}