package handlers

import (
	"encoding/json"
	"fmt"
	"log"
	"net/http"

	c "github.com/juanatsap/cv-site/internal/constants"
)

// ErrorResponse represents a structured error response
type ErrorResponse struct {
	Error   string `json:"error"`
	Message string `json:"message,omitempty"`
	Code    int    `json:"code"`
}

// AppError represents an application error with context
type AppError struct {
	Err        error
	Message    string
	StatusCode int
	Internal   bool // If true, don't expose details to client
}

// Error implements the error interface
func (e *AppError) Error() string {
	if e.Err != nil {
		return e.Err.Error()
	}
	return e.Message
}

// NewAppError creates a new application error
func NewAppError(err error, message string, statusCode int, internal bool) *AppError {
	return &AppError{
		Err:        err,
		Message:    message,
		StatusCode: statusCode,
		Internal:   internal,
	}
}

// HandleError handles errors consistently across the application
func HandleError(w http.ResponseWriter, r *http.Request, err error) {
	var appErr *AppError

	// Check if it's an AppError
	switch e := err.(type) {
	case *AppError:
		appErr = e
	default:
		// Unknown error - treat as internal server error
		appErr = NewAppError(err, "Internal Server Error", http.StatusInternalServerError, true)
	}

	// Log the error
	if appErr.Internal {
		log.Printf("ERROR [%s %s]: %v", r.Method, r.URL.Path, appErr.Err)
	} else {
		log.Printf("CLIENT ERROR [%s %s]: %s (status: %d)", r.Method, r.URL.Path, appErr.Message, appErr.StatusCode)
	}

	// Determine response based on Accept header
	accept := r.Header.Get(c.HeaderAccept)
	isJSON := accept == c.ContentTypeJSON
	isHTMX := r.Header.Get(c.HeaderHXRequest) != ""

	if isJSON {
		// JSON response
		w.Header().Set(c.HeaderContentType, c.ContentTypeJSON)
		w.WriteHeader(appErr.StatusCode)

		response := ErrorResponse{
			Error: http.StatusText(appErr.StatusCode),
			Code:  appErr.StatusCode,
		}

		// Only include message if not internal
		if !appErr.Internal {
			response.Message = appErr.Message
		}

		if err := json.NewEncoder(w).Encode(response); err != nil {
			log.Printf("ERROR encoding JSON response: %v", err)
		}
		return
	}

	if isHTMX {
		// HTMX response - return simple HTML fragment
		w.Header().Set(c.HeaderContentType, c.ContentTypeHTMLFragment)
		w.WriteHeader(appErr.StatusCode)

		message := appErr.Message
		if appErr.Internal {
			message = "An error occurred. Please try again later."
		}

		if _, err := w.Write([]byte("<div class='error'>" + message + "</div>")); err != nil {
			log.Printf("ERROR writing HTMX error response: %v", err)
		}
		return
	}

	// Standard HTTP error response
	message := appErr.Message
	if appErr.Internal {
		message = "Internal Server Error"
	}

	http.Error(w, message, appErr.StatusCode)
}

// Common error constructors

func NotFoundError(message string) *AppError {
	return NewAppError(nil, message, http.StatusNotFound, false)
}

func BadRequestError(message string) *AppError {
	return NewAppError(nil, message, http.StatusBadRequest, false)
}

func InternalError(err error) *AppError {
	return NewAppError(err, "Internal Server Error", http.StatusInternalServerError, true)
}

func TemplateError(err error, templateName string) *AppError {
	return NewAppError(
		err,
		"Error rendering template: "+templateName,
		http.StatusInternalServerError,
		true,
	)
}

func DataLoadError(err error, dataType string) *AppError {
	return NewAppError(
		err,
		"Error loading "+dataType+" data",
		http.StatusInternalServerError,
		true,
	)
}

// ==============================================================================
// TYPED ERRORS
// Domain-specific error types for better error handling
// ==============================================================================

// ErrorCode represents a specific error condition
type ErrorCode string

const (
	ErrCodeInvalidLanguage   ErrorCode = "INVALID_LANGUAGE"
	ErrCodeInvalidLength     ErrorCode = "INVALID_LENGTH"
	ErrCodeInvalidIcons      ErrorCode = "INVALID_ICONS"
	ErrCodeInvalidTheme      ErrorCode = "INVALID_THEME"
	ErrCodeInvalidVersion    ErrorCode = "INVALID_VERSION"
	ErrCodeTemplateNotFound  ErrorCode = "TEMPLATE_NOT_FOUND"
	ErrCodeTemplateRender    ErrorCode = "TEMPLATE_RENDER"
	ErrCodeDataLoad          ErrorCode = "DATA_LOAD"
	ErrCodePDFGeneration     ErrorCode = "PDF_GENERATION"
	ErrCodeMethodNotAllowed  ErrorCode = "METHOD_NOT_ALLOWED"
	ErrCodeUnauthorized      ErrorCode = "UNAUTHORIZED"
	ErrCodeForbidden         ErrorCode = "FORBIDDEN"
	ErrCodeRateLimitExceeded ErrorCode = "RATE_LIMIT_EXCEEDED"
)

// DomainError represents a domain-specific error
type DomainError struct {
	Code       ErrorCode
	Message    string
	Err        error
	StatusCode int
	Field      string // Optional field that caused the error
}

// Error implements the error interface
func (e *DomainError) Error() string {
	if e.Err != nil {
		return fmt.Sprintf("%s: %v", e.Code, e.Err)
	}
	return fmt.Sprintf("%s: %s", e.Code, e.Message)
}

// Unwrap returns the underlying error
func (e *DomainError) Unwrap() error {
	return e.Err
}

// NewDomainError creates a new domain error
func NewDomainError(code ErrorCode, message string, statusCode int) *DomainError {
	return &DomainError{
		Code:       code,
		Message:    message,
		StatusCode: statusCode,
	}
}

// WithError adds an underlying error
func (e *DomainError) WithError(err error) *DomainError {
	e.Err = err
	return e
}

// WithField adds field information
func (e *DomainError) WithField(field string) *DomainError {
	e.Field = field
	return e
}

// NOTE: Domain error constructors were removed as they were unused.
// If needed in the future, they can be re-added following the DomainError pattern above.
// See git history for the previous implementation.