package api

import (
	"context"
	"errors"
	"net/http"
	"time"

	"go.uber.org/zap"

	"predictor-refactored/internal/api/async"
	"predictor-refactored/internal/datasets"
	"predictor-refactored/internal/elevation"
	"predictor-refactored/internal/engine"
	"predictor-refactored/internal/metrics"
	"predictor-refactored/internal/windviz"
	apirest "predictor-refactored/pkg/rest"
)

// Handler implements the ogen-generated apirest.Handler interface for every
// operation in the OpenAPI spec. Operation methods are grouped by concern
// across prediction.go, datasets.go, and wind.go.
type Handler struct {
	mgr     *datasets.Manager
	elev    *elevation.Dataset
	async   *async.Manager
	metrics metrics.Sink
	cache   *windviz.Cache
	started time.Time
	log     *zap.Logger
}

var _ apirest.Handler = (*Handler)(nil)

// terrain returns the elevation dataset as an engine.TerrainProvider, or an
// untyped nil interface when no elevation dataset is loaded. Returning the
// concrete nil *elevation.Dataset directly would produce a non-nil interface
// wrapping a nil pointer, which then panics on first use — so the nil check
// must happen here, on the concrete type.
func (h *Handler) terrain() engine.TerrainProvider {
	if h.elev == nil {
		return nil
	}
	return h.elev
}

// NewError converts an error returned by a handler into the spec's default
// error response. Handlers return *apirest.DefaultErrorStatusCode (via the
// apiError helper) to control the status code; anything else is a 500.
func (h *Handler) NewError(_ context.Context, err error) *apirest.DefaultErrorStatusCode {
	var coded *apirest.DefaultErrorStatusCode
	if errors.As(err, &coded) {
		return coded
	}
	h.log.Error("unhandled handler error", zap.Error(err))
	return apiError(http.StatusInternalServerError, err.Error())
}

// apiError builds a coded error response carrying an HTTP status.
func apiError(status int, description string) *apirest.DefaultErrorStatusCode {
	return &apirest.DefaultErrorStatusCode{
		StatusCode: status,
		Response: apirest.Error{
			Error: apirest.ErrorError{
				Type:        http.StatusText(status),
				Description: description,
			},
		},
	}
}