// Package handlers provides core API handler functionality for the CLI Proxy API server.
// It includes common types, client management, load balancing, and error handling
// shared across all API endpoint handlers (OpenAI, Claude, Gemini).
package handlers

import (
	"fmt"
	"net/http"

	"github.com/gin-gonic/gin"
	"github.com/router-for-me/CLIProxyAPI/v6/internal/config"
	"github.com/router-for-me/CLIProxyAPI/v6/internal/interfaces"
	"github.com/router-for-me/CLIProxyAPI/v6/internal/util"
	coreauth "github.com/router-for-me/CLIProxyAPI/v6/sdk/cliproxy/auth"
	coreexecutor "github.com/router-for-me/CLIProxyAPI/v6/sdk/cliproxy/executor"
	sdktranslator "github.com/router-for-me/CLIProxyAPI/v6/sdk/translator"
	"golang.org/x/net/context"
)

// ErrorResponse represents a standard error response format for the API.
// It contains a single ErrorDetail field.
type ErrorResponse struct {
	// Error contains detailed information about the error that occurred.
	Error ErrorDetail `json:"error"`
}

// ErrorDetail provides specific information about an error that occurred.
// It includes a human-readable message, an error type, and an optional error code.
type ErrorDetail struct {
	// Message is a human-readable message providing more details about the error.
	Message string `json:"message"`

	// Type is the category of error that occurred (e.g., "invalid_request_error").
	Type string `json:"type"`

	// Code is a short code identifying the error, if applicable.
	Code string `json:"code,omitempty"`
}

// BaseAPIHandler contains the handlers for API endpoints.
// It holds a pool of clients to interact with the backend service and manages
// load balancing, client selection, and configuration.
type BaseAPIHandler struct {
	// AuthManager manages auth lifecycle and execution in the new architecture.
	AuthManager *coreauth.Manager

	// Cfg holds the current application configuration.
	Cfg *config.Config
}

// NewBaseAPIHandlers creates a new API handlers instance.
// It takes a slice of clients and configuration as input.
//
// Parameters:
//   - cliClients: A slice of AI service clients
//   - cfg: The application configuration
//
// Returns:
//   - *BaseAPIHandler: A new API handlers instance
func NewBaseAPIHandlers(cfg *config.Config, authManager *coreauth.Manager) *BaseAPIHandler {
	return &BaseAPIHandler{
		Cfg:         cfg,
		AuthManager: authManager,
	}
}

// UpdateClients updates the handlers' client list and configuration.
// This method is called when the configuration or authentication tokens change.
//
// Parameters:
//   - clients: The new slice of AI service clients
//   - cfg: The new application configuration
func (h *BaseAPIHandler) UpdateClients(cfg *config.Config) { h.Cfg = cfg }

// GetAlt extracts the 'alt' parameter from the request query string.
// It checks both 'alt' and '$alt' parameters and returns the appropriate value.
//
// Parameters:
//   - c: The Gin context containing the HTTP request
//
// Returns:
//   - string: The alt parameter value, or empty string if it's "sse"
func (h *BaseAPIHandler) GetAlt(c *gin.Context) string {
	var alt string
	var hasAlt bool
	alt, hasAlt = c.GetQuery("alt")
	if !hasAlt {
		alt, _ = c.GetQuery("$alt")
	}
	if alt == "sse" {
		return ""
	}
	return alt
}

// GetContextWithCancel creates a new context with cancellation capabilities.
// It embeds the Gin context and the API handler into the new context for later use.
// The returned cancel function also handles logging the API response if request logging is enabled.
//
// Parameters:
//   - handler: The API handler associated with the request.
//   - c: The Gin context of the current request.
//   - ctx: The parent context.
//
// Returns:
//   - context.Context: The new context with cancellation and embedded values.
//   - APIHandlerCancelFunc: A function to cancel the context and log the response.
func (h *BaseAPIHandler) GetContextWithCancel(handler interfaces.APIHandler, c *gin.Context, ctx context.Context) (context.Context, APIHandlerCancelFunc) {
	newCtx, cancel := context.WithCancel(ctx)
	newCtx = context.WithValue(newCtx, "gin", c)
	newCtx = context.WithValue(newCtx, "handler", handler)
	return newCtx, func(params ...interface{}) {
		if h.Cfg.RequestLog {
			if len(params) == 1 {
				data := params[0]
				switch data.(type) {
				case []byte:
					c.Set("API_RESPONSE", data.([]byte))
				case error:
					c.Set("API_RESPONSE", []byte(data.(error).Error()))
				case string:
					c.Set("API_RESPONSE", []byte(data.(string)))
				case bool:
				case nil:
				}
			}
		}

		cancel()
	}
}

// ExecuteWithAuthManager executes a non-streaming request via the core auth manager.
// This path is the only supported execution route.
func (h *BaseAPIHandler) ExecuteWithAuthManager(ctx context.Context, handlerType, modelName string, rawJSON []byte, alt string) ([]byte, *interfaces.ErrorMessage) {
	providers := util.GetProviderName(modelName, h.Cfg)
	if len(providers) == 0 {
		return nil, &interfaces.ErrorMessage{StatusCode: http.StatusBadRequest, Error: fmt.Errorf("unknown provider for model %s", modelName)}
	}
	req := coreexecutor.Request{
		Model:   modelName,
		Payload: cloneBytes(rawJSON),
	}
	opts := coreexecutor.Options{
		Stream:          false,
		Alt:             alt,
		OriginalRequest: cloneBytes(rawJSON),
		SourceFormat:    sdktranslator.FromString(handlerType),
	}
	resp, err := h.AuthManager.Execute(ctx, providers, req, opts)
	if err != nil {
		return nil, &interfaces.ErrorMessage{StatusCode: http.StatusInternalServerError, Error: err}
	}
	return cloneBytes(resp.Payload), nil
}

// ExecuteCountWithAuthManager executes a non-streaming request via the core auth manager.
// This path is the only supported execution route.
func (h *BaseAPIHandler) ExecuteCountWithAuthManager(ctx context.Context, handlerType, modelName string, rawJSON []byte, alt string) ([]byte, *interfaces.ErrorMessage) {
	providers := util.GetProviderName(modelName, h.Cfg)
	if len(providers) == 0 {
		return nil, &interfaces.ErrorMessage{StatusCode: http.StatusBadRequest, Error: fmt.Errorf("unknown provider for model %s", modelName)}
	}
	req := coreexecutor.Request{
		Model:   modelName,
		Payload: cloneBytes(rawJSON),
	}
	opts := coreexecutor.Options{
		Stream:          false,
		Alt:             alt,
		OriginalRequest: cloneBytes(rawJSON),
		SourceFormat:    sdktranslator.FromString(handlerType),
	}
	resp, err := h.AuthManager.ExecuteCount(ctx, providers, req, opts)
	if err != nil {
		return nil, &interfaces.ErrorMessage{StatusCode: http.StatusInternalServerError, Error: err}
	}
	return cloneBytes(resp.Payload), nil
}

// ExecuteStreamWithAuthManager executes a streaming request via the core auth manager.
// This path is the only supported execution route.
func (h *BaseAPIHandler) ExecuteStreamWithAuthManager(ctx context.Context, handlerType, modelName string, rawJSON []byte, alt string) (<-chan []byte, <-chan *interfaces.ErrorMessage) {
	providers := util.GetProviderName(modelName, h.Cfg)
	if len(providers) == 0 {
		errChan := make(chan *interfaces.ErrorMessage, 1)
		errChan <- &interfaces.ErrorMessage{StatusCode: http.StatusBadRequest, Error: fmt.Errorf("unknown provider for model %s", modelName)}
		close(errChan)
		return nil, errChan
	}
	req := coreexecutor.Request{
		Model:   modelName,
		Payload: cloneBytes(rawJSON),
	}
	opts := coreexecutor.Options{
		Stream:          true,
		Alt:             alt,
		OriginalRequest: cloneBytes(rawJSON),
		SourceFormat:    sdktranslator.FromString(handlerType),
	}
	chunks, err := h.AuthManager.ExecuteStream(ctx, providers, req, opts)
	if err != nil {
		errChan := make(chan *interfaces.ErrorMessage, 1)
		errChan <- &interfaces.ErrorMessage{StatusCode: http.StatusInternalServerError, Error: err}
		close(errChan)
		return nil, errChan
	}
	dataChan := make(chan []byte)
	errChan := make(chan *interfaces.ErrorMessage, 1)
	go func() {
		defer close(dataChan)
		defer close(errChan)
		for chunk := range chunks {
			if chunk.Err != nil {
				errChan <- &interfaces.ErrorMessage{StatusCode: http.StatusInternalServerError, Error: chunk.Err}
				return
			}
			if len(chunk.Payload) > 0 {
				dataChan <- cloneBytes(chunk.Payload)
			}
		}
	}()
	return dataChan, errChan
}

func cloneBytes(src []byte) []byte {
	if len(src) == 0 {
		return nil
	}
	dst := make([]byte, len(src))
	copy(dst, src)
	return dst
}

// WriteErrorResponse writes an error message to the response writer using the HTTP status embedded in the message.
func (h *BaseAPIHandler) WriteErrorResponse(c *gin.Context, msg *interfaces.ErrorMessage) {
	status := http.StatusInternalServerError
	if msg != nil && msg.StatusCode > 0 {
		status = msg.StatusCode
	}
	c.Status(status)
	if msg != nil && msg.Error != nil {
		_, _ = c.Writer.Write([]byte(msg.Error.Error()))
	} else {
		_, _ = c.Writer.Write([]byte(http.StatusText(status)))
	}
}

func (h *BaseAPIHandler) LoggingAPIResponseError(ctx context.Context, err *interfaces.ErrorMessage) {
	if h.Cfg.RequestLog {
		if ginContext, ok := ctx.Value("gin").(*gin.Context); ok {
			if apiResponseErrors, isExist := ginContext.Get("API_RESPONSE_ERROR"); isExist {
				if slicesAPIResponseError, isOk := apiResponseErrors.([]*interfaces.ErrorMessage); isOk {
					slicesAPIResponseError = append(slicesAPIResponseError, err)
					ginContext.Set("API_RESPONSE_ERROR", slicesAPIResponseError)
				}
			} else {
				// Create new response data entry
				ginContext.Set("API_RESPONSE_ERROR", []*interfaces.ErrorMessage{err})
			}
		}
	}
}

// APIHandlerCancelFunc is a function type for canceling an API handler's context.
// It can optionally accept parameters, which are used for logging the response.
type APIHandlerCancelFunc func(params ...interface{})