fetch_ml/internal/api/errors/errors.go

// Package errors provides centralized error handling for the API
package errors

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

	"github.com/gorilla/websocket"
)

// Error codes - centralized to ensure consistency across all API handlers
const (
	CodeUnknownError          = "UNKNOWN_ERROR"
	CodeInvalidRequest        = "INVALID_REQUEST"
	CodeAuthenticationFailed  = "AUTHENTICATION_FAILED"
	CodePermissionDenied      = "PERMISSION_DENIED"
	CodeResourceNotFound      = "RESOURCE_NOT_FOUND"
	CodeResourceAlreadyExists = "RESOURCE_ALREADY_EXISTS"
	CodeServerOverloaded      = "SERVER_OVERLOADED"
	CodeDatabaseError         = "DATABASE_ERROR"
	CodeNetworkError          = "NETWORK_ERROR"
	CodeStorageError          = "STORAGE_ERROR"
	CodeTimeout               = "TIMEOUT"
	CodeJobNotFound           = "JOB_NOT_FOUND"
	CodeJobAlreadyRunning     = "JOB_ALREADY_RUNNING"
	CodeJobFailedToStart      = "JOB_FAILED_TO_START"
	CodeJobExecutionFailed    = "JOB_EXECUTION_FAILED"
	CodeJobCancelled          = "JOB_CANCELLED"
	CodeOutOfMemory           = "OUT_OF_MEMORY"
	CodeDiskFull              = "DISK_FULL"
	CodeInvalidConfiguration  = "INVALID_CONFIGURATION"
	CodeServiceUnavailable    = "SERVICE_UNAVAILABLE"
	CodeBadRequest            = "BAD_REQUEST"
	CodeForbidden             = "FORBIDDEN"
	CodeNotFound              = "NOT_FOUND"
)

// ErrorResponse represents a standardized error response
type ErrorResponse struct {
	ErrorMsg string `json:"error"`
	Code     string `json:"code"`
	Message  string `json:"message,omitempty"`
	Details  string `json:"details,omitempty"`
}

// NewErrorResponse creates a new error response
func NewErrorResponse(code, message, details string) ErrorResponse {
	return ErrorResponse{
		ErrorMsg: "true",
		Code:     code,
		Message:  message,
		Details:  details,
	}
}

// Error implements the error interface
func (e ErrorResponse) Error() string {
	if e.Details != "" {
		return fmt.Sprintf("[%s] %s: %s", e.Code, e.Message, e.Details)
	}
	return fmt.Sprintf("[%s] %s", e.Code, e.Message)
}

// WriteHTTPError writes an error response to an HTTP ResponseWriter
func WriteHTTPError(w http.ResponseWriter, statusCode int, errCode, message, details string) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(statusCode)
	resp := NewErrorResponse(errCode, message, details)
	_ = json.NewEncoder(w).Encode(resp)
}

// WriteHTTPErrorFromError writes an error response from an error
func WriteHTTPErrorFromError(w http.ResponseWriter, statusCode int, err error) {
	if errResp, ok := err.(ErrorResponse); ok {
		WriteHTTPError(w, statusCode, errResp.Code, errResp.Message, errResp.Details)
		return
	}
	WriteHTTPError(w, statusCode, CodeUnknownError, err.Error(), "")
}

// SendErrorPacket sends an error packet over WebSocket
func SendErrorPacket(conn *websocket.Conn, code, message, details string) error {
	resp := NewErrorResponse(code, message, details)
	return conn.WriteJSON(resp)
}

// SendSuccessPacket sends a success packet over WebSocket
// Automatically adds "success": true to the response
func SendSuccessPacket(conn *websocket.Conn, data map[string]any) error {
	response := make(map[string]any, len(data)+1)
	response["success"] = true
	for k, v := range data {
		response[k] = v
	}
	return conn.WriteJSON(response)
}

// Common error responses as typed errors for use with errors.Is/errors.As

var (
	ErrNotFound           = NewErrorResponse(CodeNotFound, "resource not found", "")
	ErrPermissionDenied   = NewErrorResponse(CodePermissionDenied, "permission denied", "")
	ErrInvalidRequest     = NewErrorResponse(CodeInvalidRequest, "invalid request", "")
	ErrServiceUnavailable = NewErrorResponse(CodeServiceUnavailable, "service unavailable", "")
	ErrServerOverloaded   = NewErrorResponse(CodeServerOverloaded, "server overloaded", "")
)

// HTTPStatusFromCode maps error codes to HTTP status codes
func HTTPStatusFromCode(code string) int {
	switch code {
	case CodeInvalidRequest, CodeBadRequest:
		return http.StatusBadRequest
	case CodeAuthenticationFailed:
		return http.StatusUnauthorized
	case CodePermissionDenied, CodeForbidden:
		return http.StatusForbidden
	case CodeResourceNotFound, CodeNotFound, CodeJobNotFound:
		return http.StatusNotFound
	case CodeResourceAlreadyExists:
		return http.StatusConflict
	case CodeServerOverloaded, CodeServiceUnavailable:
		return http.StatusServiceUnavailable
	case CodeTimeout:
		return http.StatusRequestTimeout
	default:
		return http.StatusInternalServerError
	}
}