// 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"
	"sync"

	"github.com/gin-gonic/gin"
	. "github.com/router-for-me/CLIProxyAPI/v6/internal/constant"
	"github.com/router-for-me/CLIProxyAPI/v6/internal/interfaces"
	"github.com/router-for-me/CLIProxyAPI/v6/internal/registry"
	responsesconverter "github.com/router-for-me/CLIProxyAPI/v6/internal/translator/openai/openai/responses"
	"github.com/router-for-me/CLIProxyAPI/v6/sdk/api/handlers"
	"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) {
	// Get all available models
	allModels := h.Models()

	// Filter to only include the 4 required fields: id, object, created, owned_by
	filteredModels := make([]map[string]any, len(allModels))
	for i, model := range allModels {
		filteredModel := map[string]any{
			"id":     model["id"],
			"object": model["object"],
		}

		// Add created field if it exists
		if created, exists := model["created"]; exists {
			filteredModel["created"] = created
		}

		// Add owned_by field if it exists
		if ownedBy, exists := model["owned_by"]; exists {
			filteredModel["owned_by"] = ownedBy
		}

		filteredModels[i] = filteredModel
	}

	c.JSON(http.StatusOK, gin.H{
		"object": "list",
		"data":   filteredModels,
	})
}

// 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")
	stream := streamResult.Type == gjson.True

	// Some clients send OpenAI Responses-format payloads to /v1/chat/completions.
	// Convert them to Chat Completions so downstream translators preserve tool metadata.
	if shouldTreatAsResponsesFormat(rawJSON) {
		modelName := gjson.GetBytes(rawJSON, "model").String()
		rawJSON = responsesconverter.ConvertOpenAIResponsesRequestToOpenAIChatCompletions(modelName, rawJSON, stream)
		stream = gjson.GetBytes(rawJSON, "stream").Bool()
	}

	if stream {
		h.handleStreamingResponse(c, rawJSON)
	} else {
		h.handleNonStreamingResponse(c, rawJSON)
	}

}

// shouldTreatAsResponsesFormat detects OpenAI Responses-style payloads that are
// accidentally sent to the Chat Completions endpoint.
func shouldTreatAsResponsesFormat(rawJSON []byte) bool {
	if gjson.GetBytes(rawJSON, "messages").Exists() {
		return false
	}
	if gjson.GetBytes(rawJSON, "input").Exists() {
		return true
	}
	if gjson.GetBytes(rawJSON, "instructions").Exists() {
		return true
	}
	return false
}

// 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())
	resp, errMsg := h.ExecuteWithAuthManager(cliCtx, h.HandlerType(), modelName, rawJSON, h.GetAlt(c))
	if errMsg != nil {
		h.WriteErrorResponse(c, errMsg)
		cliCancel(errMsg.Error)
		return
	}
	_, _ = c.Writer.Write(resp)
	cliCancel()
}

// 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) {
	// 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())
	dataChan, errChan := h.ExecuteStreamWithAuthManager(cliCtx, h.HandlerType(), modelName, rawJSON, h.GetAlt(c))

	setSSEHeaders := func() {
		c.Header("Content-Type", "text/event-stream")
		c.Header("Cache-Control", "no-cache")
		c.Header("Connection", "keep-alive")
		c.Header("Access-Control-Allow-Origin", "*")
	}

	// Peek at the first chunk to determine success or failure before setting headers
	for {
		select {
		case <-c.Request.Context().Done():
			cliCancel(c.Request.Context().Err())
			return
		case errMsg, ok := <-errChan:
			if !ok {
				// Err channel closed cleanly; wait for data channel.
				errChan = nil
				continue
			}
			// Upstream failed immediately. Return proper error status and JSON.
			h.WriteErrorResponse(c, errMsg)
			if errMsg != nil {
				cliCancel(errMsg.Error)
			} else {
				cliCancel(nil)
			}
			return
		case chunk, ok := <-dataChan:
			if !ok {
				// Stream closed without data? Send DONE or just headers.
				setSSEHeaders()
				_, _ = fmt.Fprintf(c.Writer, "data: [DONE]\n\n")
				flusher.Flush()
				cliCancel(nil)
				return
			}

			// Success! Commit to streaming headers.
			setSSEHeaders()

			_, _ = fmt.Fprintf(c.Writer, "data: %s\n\n", string(chunk))
			flusher.Flush()

			// Continue streaming the rest
			h.handleStreamResult(c, flusher, func(err error) { cliCancel(err) }, dataChan, errChan)
			return
		}
	}
}

// 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())
	stopKeepAlive := h.StartNonStreamingKeepAlive(c, cliCtx)
	resp, errMsg := h.ExecuteWithAuthManager(cliCtx, h.HandlerType(), modelName, chatCompletionsJSON, "")
	stopKeepAlive()
	if errMsg != nil {
		h.WriteErrorResponse(c, errMsg)
		cliCancel(errMsg.Error)
		return
	}
	completionsResp := convertChatCompletionsResponseToCompletions(resp)
	_, _ = c.Writer.Write(completionsResp)
	cliCancel()
}

// 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) {
	// 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())
	dataChan, errChan := h.ExecuteStreamWithAuthManager(cliCtx, h.HandlerType(), modelName, chatCompletionsJSON, "")

	setSSEHeaders := func() {
		c.Header("Content-Type", "text/event-stream")
		c.Header("Cache-Control", "no-cache")
		c.Header("Connection", "keep-alive")
		c.Header("Access-Control-Allow-Origin", "*")
	}

	// Peek at the first chunk
	for {
		select {
		case <-c.Request.Context().Done():
			cliCancel(c.Request.Context().Err())
			return
		case errMsg, ok := <-errChan:
			if !ok {
				// Err channel closed cleanly; wait for data channel.
				errChan = nil
				continue
			}
			h.WriteErrorResponse(c, errMsg)
			if errMsg != nil {
				cliCancel(errMsg.Error)
			} else {
				cliCancel(nil)
			}
			return
		case chunk, ok := <-dataChan:
			if !ok {
				setSSEHeaders()
				_, _ = fmt.Fprintf(c.Writer, "data: [DONE]\n\n")
				flusher.Flush()
				cliCancel(nil)
				return
			}

			// Success! Set headers.
			setSSEHeaders()

			// Write the first chunk
			converted := convertChatCompletionsStreamChunkToCompletions(chunk)
			if converted != nil {
				_, _ = fmt.Fprintf(c.Writer, "data: %s\n\n", string(converted))
				flusher.Flush()
			}

			done := make(chan struct{})
			var doneOnce sync.Once
			stop := func() { doneOnce.Do(func() { close(done) }) }

			convertedChan := make(chan []byte)
			go func() {
				defer close(convertedChan)
				for {
					select {
					case <-done:
						return
					case chunk, ok := <-dataChan:
						if !ok {
							return
						}
						converted := convertChatCompletionsStreamChunkToCompletions(chunk)
						if converted == nil {
							continue
						}
						select {
						case <-done:
							return
						case convertedChan <- converted:
						}
					}
				}
			}()

			h.handleStreamResult(c, flusher, func(err error) {
				stop()
				cliCancel(err)
			}, convertedChan, errChan)
			return
		}
	}
}
func (h *OpenAIAPIHandler) handleStreamResult(c *gin.Context, flusher http.Flusher, cancel func(error), data <-chan []byte, errs <-chan *interfaces.ErrorMessage) {
	h.ForwardStream(c, flusher, cancel, data, errs, handlers.StreamForwardOptions{
		WriteChunk: func(chunk []byte) {
			_, _ = fmt.Fprintf(c.Writer, "data: %s\n\n", string(chunk))
		},
		WriteTerminalError: func(errMsg *interfaces.ErrorMessage) {
			if errMsg == nil {
				return
			}
			status := http.StatusInternalServerError
			if errMsg.StatusCode > 0 {
				status = errMsg.StatusCode
			}
			errText := http.StatusText(status)
			if errMsg.Error != nil && errMsg.Error.Error() != "" {
				errText = errMsg.Error.Error()
			}
			body := handlers.BuildErrorResponseBody(status, errText)
			_, _ = fmt.Fprintf(c.Writer, "data: %s\n\n", string(body))
		},
		WriteDone: func() {
			_, _ = fmt.Fprint(c.Writer, "data: [DONE]\n\n")
		},
	})
}