package httpapi

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

	"ai-workflow-skill/packages/coord-core/store"
)

type errorEnvelope struct {
	Error errorPayload `json:"error"`
}

type errorPayload struct {
	Code    string `json:"code"`
	Message string `json:"message"`
}

func writeJSON(w http.ResponseWriter, status int, payload any) {
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	w.WriteHeader(status)

	enc := json.NewEncoder(w)
	enc.SetIndent("", "  ")
	_ = enc.Encode(payload)
}

func writeError(w http.ResponseWriter, err error) {
	status, code := classifyError(err)
	writeJSON(w, status, errorEnvelope{
		Error: errorPayload{
			Code:    code,
			Message: errorMessage(err),
		},
	})
}

func classifyError(err error) (int, string) {
	switch {
	case errors.Is(err, store.ErrInvalidInput):
		return http.StatusBadRequest, "invalid_input"
	case errors.Is(err, store.ErrRunNotFound), errors.Is(err, store.ErrTaskNotFound), errors.Is(err, store.ErrThreadNotFound):
		return http.StatusNotFound, "not_found"
	case errors.Is(err, store.ErrInvalidState):
		return http.StatusConflict, "invalid_state"
	default:
		return http.StatusInternalServerError, "internal_error"
	}
}

func errorMessage(err error) string {
	if err == nil {
		return "unknown error"
	}
	return fmt.Sprintf("%v", err)
}