// Package gemini provides HTTP handlers for Gemini CLI API functionality.
// This package implements handlers that process CLI-specific requests for Gemini API operations,
// including content generation and streaming content generation endpoints.
// The handlers restrict access to localhost only and manage communication with the backend service.
package gemini

import (
	"bytes"
	"context"
	"fmt"
	"io"
	"net/http"
	"strings"
	"time"

	"github.com/gin-gonic/gin"
	"github.com/router-for-me/CLIProxyAPI/v6/internal/api/handlers"
	. "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/util"
	log "github.com/sirupsen/logrus"
	"github.com/tidwall/gjson"
)

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

// NewGeminiCLIAPIHandler creates a new Gemini CLI API handlers instance.
// It takes an BaseAPIHandler instance as input and returns a GeminiCLIAPIHandler.
func NewGeminiCLIAPIHandler(apiHandlers *handlers.BaseAPIHandler) *GeminiCLIAPIHandler {
	return &GeminiCLIAPIHandler{
		BaseAPIHandler: apiHandlers,
	}
}

// HandlerType returns the type of this handler.
func (h *GeminiCLIAPIHandler) HandlerType() string {
	return GeminiCLI
}

// Models returns a list of models supported by this handler.
func (h *GeminiCLIAPIHandler) Models() []map[string]any {
	return make([]map[string]any, 0)
}

// CLIHandler handles CLI-specific requests for Gemini API operations.
// It restricts access to localhost only and routes requests to appropriate internal handlers.
func (h *GeminiCLIAPIHandler) CLIHandler(c *gin.Context) {
	if !strings.HasPrefix(c.Request.RemoteAddr, "127.0.0.1:") {
		c.JSON(http.StatusForbidden, handlers.ErrorResponse{
			Error: handlers.ErrorDetail{
				Message: "CLI reply only allow local access",
				Type:    "forbidden",
			},
		})
		return
	}

	rawJSON, _ := c.GetRawData()
	requestRawURI := c.Request.URL.Path

	if requestRawURI == "/v1internal:generateContent" {
		h.handleInternalGenerateContent(c, rawJSON)
	} else if requestRawURI == "/v1internal:streamGenerateContent" {
		h.handleInternalStreamGenerateContent(c, rawJSON)
	} else {
		reqBody := bytes.NewBuffer(rawJSON)
		req, err := http.NewRequest("POST", fmt.Sprintf("https://cloudcode-pa.googleapis.com%s", c.Request.URL.RequestURI()), reqBody)
		if err != nil {
			c.JSON(http.StatusBadRequest, handlers.ErrorResponse{
				Error: handlers.ErrorDetail{
					Message: fmt.Sprintf("Invalid request: %v", err),
					Type:    "invalid_request_error",
				},
			})
			return
		}
		for key, value := range c.Request.Header {
			req.Header[key] = value
		}

		httpClient := util.SetProxy(h.Cfg, &http.Client{})

		resp, err := httpClient.Do(req)
		if err != nil {
			c.JSON(http.StatusBadRequest, handlers.ErrorResponse{
				Error: handlers.ErrorDetail{
					Message: fmt.Sprintf("Invalid request: %v", err),
					Type:    "invalid_request_error",
				},
			})
			return
		}

		if resp.StatusCode < 200 || resp.StatusCode >= 300 {
			defer func() {
				if err = resp.Body.Close(); err != nil {
					log.Printf("warn: failed to close response body: %v", err)
				}
			}()
			bodyBytes, _ := io.ReadAll(resp.Body)

			c.JSON(http.StatusBadRequest, handlers.ErrorResponse{
				Error: handlers.ErrorDetail{
					Message: string(bodyBytes),
					Type:    "invalid_request_error",
				},
			})
			return
		}

		defer func() {
			_ = resp.Body.Close()
		}()

		for key, value := range resp.Header {
			c.Header(key, value[0])
		}
		output, err := io.ReadAll(resp.Body)
		if err != nil {
			log.Errorf("Failed to read response body: %v", err)
			return
		}
		_, _ = c.Writer.Write(output)
		c.Set("API_RESPONSE", output)
	}
}

// handleInternalStreamGenerateContent handles streaming content generation requests.
// It sets up a server-sent event stream and forwards the request to the backend client.
// The function continuously proxies response chunks from the backend to the client.
func (h *GeminiCLIAPIHandler) handleInternalStreamGenerateContent(c *gin.Context, rawJSON []byte) {
	alt := h.GetAlt(c)

	if alt == "" {
		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
	}

	modelResult := gjson.GetBytes(rawJSON, "model")
	modelName := modelResult.String()

	cliCtx, cliCancel := h.GetContextWithCancel(h, c, context.Background())
	dataChan, errChan := h.ExecuteStreamWithAuthManager(cliCtx, h.HandlerType(), modelName, rawJSON, "")
	h.forwardCLIStream(c, flusher, "", func(err error) { cliCancel(err) }, dataChan, errChan)
	return
}

// handleInternalGenerateContent handles non-streaming content generation requests.
// It sends a request to the backend client and proxies the entire response back to the client at once.
func (h *GeminiCLIAPIHandler) handleInternalGenerateContent(c *gin.Context, rawJSON []byte) {
	c.Header("Content-Type", "application/json")
	modelResult := gjson.GetBytes(rawJSON, "model")
	modelName := modelResult.String()

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

func (h *GeminiCLIAPIHandler) forwardCLIStream(c *gin.Context, flusher http.Flusher, alt string, cancel func(error), data <-chan []byte, errs <-chan *interfaces.ErrorMessage) {
	for {
		select {
		case <-c.Request.Context().Done():
			cancel(c.Request.Context().Err())
			return
		case chunk, ok := <-data:
			if !ok {
				cancel(nil)
				return
			}
			if alt == "" {
				if bytes.Equal(chunk, []byte("data: [DONE]")) || bytes.Equal(chunk, []byte("[DONE]")) {
					continue
				}

				if !bytes.HasPrefix(chunk, []byte("data:")) {
					_, _ = c.Writer.Write([]byte("data: "))
				}

				_, _ = c.Writer.Write(chunk)
				_, _ = c.Writer.Write([]byte("\n\n"))
			} else {
				_, _ = c.Writer.Write(chunk)
			}
			flusher.Flush()
		case errMsg, ok := <-errs:
			if !ok {
				continue
			}
			if errMsg != nil {
				h.WriteErrorResponse(c, errMsg)
				flusher.Flush()
			}
			var execErr error
			if errMsg != nil {
				execErr = errMsg.Error
			}
			cancel(execErr)
			return
		case <-time.After(500 * time.Millisecond):
		}
	}
}