package api

import (
	"context"
	"errors"
	"fmt"
	"net/http"
	"strconv"
	"strings"
	"time"

	"github.com/gofiber/fiber/v3"
	"github.com/gofiber/fiber/v3/middleware/cors"
	"github.com/gofiber/fiber/v3/middleware/favicon"
	"github.com/gofiber/fiber/v3/middleware/logger"
	"github.com/gofiber/fiber/v3/middleware/recover"
	"github.com/gofiber/fiber/v3/middleware/static"

	"prayertimes/pkg/hijricalendar"
	"prayertimes/pkg/prayer"
	"prayertimes/templates"
)

type httpError struct {
	Message string `json:"message"`
}

type Services struct {
	PrayerProvider         PrayerProvider
	LocationProvider       LocationProvider
	LegacyLocationProvider LegacyLocationProvider
}

type PrayerProvider interface {
	Get(ctx context.Context, locationID string) (prayer.TimesResult, error)
	GetByCoords(ctx context.Context, coords prayer.Coordinates) (prayer.TimesResult, error)
}

type LocationProvider interface {
	SearchLocations(ctx context.Context, query string) ([]prayer.Location, error)
	SearchLocationsByCoords(ctx context.Context, coords prayer.Coordinates) ([]prayer.Location, error)
}

type LegacyLocationProvider interface {
	SearchLocations(ctx context.Context, query string) ([]prayer.LegacyLocation, error)
	GetLocationByID(ctx context.Context, id int) (prayer.LegacyLocation, error)
}

func New(services Services) *fiber.App {
	app := fiber.New(fiber.Config{
		Immutable:    true,
		ReadTimeout:  time.Second * 10,
		WriteTimeout: time.Second * 30,
		ErrorHandler: func(ctx fiber.Ctx, err error) error {
			if errors.Is(err, prayer.ErrInvalidLocation) {
				return ctx.Status(http.StatusUnprocessableEntity).JSON(httpError{
					Message: err.Error(),
				})
			}

			return fiber.DefaultErrorHandler(ctx, err)
		},
	})

	app.Use(
		favicon.New(),
		recover.New(recover.Config{EnableStackTrace: true}),
		logger.New(),
		cors.New(),
	)

	app.Get("/healthz", func(ctx fiber.Ctx) error {
		return ctx.SendString("OK")
	})

	app.Get("/api/v1/diyanet/prayertimes", func(ctx fiber.Ctx) error {
		var params struct {
			LocationID string   `query:"location_id"`
			Latitude   *float64 `query:"latitude"`
			Longitude  *float64 `query:"longitude"`
			UTC        bool     `query:"utc"`
		}
		if err := ctx.Bind().Query(&params); err != nil {
			return fmt.Errorf("failed to bind prayer times query parameters: %w", errors.Join(fiber.ErrBadRequest, err))
		}

		locationID := strings.TrimSpace(params.LocationID)
		utc := params.UTC

		var (
			result prayer.TimesResult
			err    error
		)

		switch {
		case locationID != "":
			result, err = services.PrayerProvider.Get(ctx.Context(), locationID)
		case params.Latitude != nil && params.Longitude != nil:
			result, err = services.PrayerProvider.GetByCoords(ctx.Context(), prayer.Coordinates{
				Latitude:  *params.Latitude,
				Longitude: *params.Longitude,
			})
		default:
			return fmt.Errorf("failed to validate prayer times query parameters: %w", fiber.ErrBadRequest)
		}

		if err != nil {
			return fmt.Errorf("failed to fetch prayer times: %w", err)
		}

		location := result.Location
		if location.Latitude != 0 || location.Longitude != 0 {
			locations, locErr := services.LocationProvider.SearchLocationsByCoords(ctx.Context(), prayer.Coordinates{
				Latitude:  location.Latitude,
				Longitude: location.Longitude,
			})
			if locErr != nil {
				return fmt.Errorf("failed to enrich prayer times location from database: %w", locErr)
			}
			if len(locations) > 0 {
				dbLocation := locations[0]
				if strings.TrimSpace(dbLocation.Timezone) == "" {
					dbLocation.Timezone = location.Timezone
				}
				location = dbLocation
			}
		}

		mappedTimes, err := mapPrayerTimesForResponse(result.Times, location, utc)
		if err != nil {
			return fmt.Errorf("failed to map prayer times for response: %w", err)
		}

		ctx.Response().Header.Set(fiber.HeaderCacheControl, "max-age=86400")
		return ctx.JSON(fiber.Map{
			"location":    location,
			"prayertimes": mappedTimes,
		})
	})

	app.Get("/api/v1/diyanet/location", func(ctx fiber.Ctx) error {
		var params struct {
			Text      *string  `query:"query"`
			Latitude  *float64 `query:"latitude"`
			Longitude *float64 `query:"longitude"`
		}
		if err := ctx.Bind().Query(&params); err != nil {
			return fmt.Errorf("failed to bind location query parameters: %w", errors.Join(fiber.ErrBadRequest, err))
		}

		var (
			locations []prayer.Location
			err       error
		)

		if params.Text != nil {
			trimmed := strings.TrimSpace(*params.Text)
			locations, err = services.LocationProvider.SearchLocations(ctx.Context(), trimmed)
		} else if params.Latitude != nil && params.Longitude != nil {
			locations, err = services.LocationProvider.SearchLocationsByCoords(ctx.Context(), prayer.Coordinates{
				Latitude:  *params.Latitude,
				Longitude: *params.Longitude,
			})
		} else {
			return fmt.Errorf("failed to validate location query parameters: %w", fiber.ErrBadRequest)
		}
		if err != nil {
			return fmt.Errorf("failed to search locations: %w", err)
		}

		ctx.Response().Header.Set(fiber.HeaderCacheControl, "max-age=86400")
		return ctx.JSON(fiber.Map{
			"locations": locations,
		})
	})

	app.Get("/api/diyanet/search", func(ctx fiber.Ctx) error {
		setDeprecationHeaders(ctx, "/api/v1/diyanet/location")

		var params struct {
			Query string `query:"q"`
		}
		if err := ctx.Bind().Query(&params); err != nil {
			return fmt.Errorf("failed to bind legacy location search query parameters: %w", errors.Join(fiber.ErrBadRequest, err))
		}

		params.Query = strings.TrimSpace(params.Query)
		if params.Query == "" {
			return fmt.Errorf("missing query parameter q: %w", fiber.ErrBadRequest)
		}

		locations, err := services.LegacyLocationProvider.SearchLocations(ctx.Context(), params.Query)
		if err != nil {
			return fmt.Errorf("failed to search legacy diyanet locations: %w", err)
		}

		resp := make([]fiber.Map, 0, len(locations))
		for _, location := range locations {
			resp = append(resp, fiber.Map{
				"id":      location.ID,
				"country": location.Country,
				"city":    location.City,
				"region":  location.Region,
			})
		}

		ctx.Response().Header.Set(fiber.HeaderCacheControl, "max-age=86400")
		return ctx.JSON(resp)
	})

	app.Get("/api/diyanet/countries", func(ctx fiber.Ctx) error {
		return respondDeprecatedEndpoint(ctx, "/api/diyanet/search?q=")
	})

	app.Get("/api/diyanet/countries/:country/cities", func(ctx fiber.Ctx) error {
		return respondDeprecatedEndpoint(ctx, "/api/diyanet/search?q=")
	})

	app.Get("/api/diyanet/locations", func(ctx fiber.Ctx) error {
		return respondDeprecatedEndpoint(ctx, "/api/diyanet/search?q=")
	})

	app.Get("/api/diyanet/prayertimes", func(ctx fiber.Ctx) error {
		setDeprecationHeaders(ctx, "/api/v1/diyanet/prayertimes")

		var params struct {
			LocationID int `query:"location_id"`
		}
		if err := ctx.Bind().Query(&params); err != nil {
			return fmt.Errorf("failed to bind legacy prayer times query parameters: %w", errors.Join(fiber.ErrBadRequest, err))
		}
		if params.LocationID <= 0 {
			return fmt.Errorf("missing query parameter location_id: %w", fiber.ErrBadRequest)
		}

		legacyLocation, err := services.LegacyLocationProvider.GetLocationByID(ctx.Context(), params.LocationID)
		if err != nil {
			return fmt.Errorf("failed to resolve location by location_id: %w", errors.Join(fiber.ErrNotFound, err))
		}

		result, err := services.PrayerProvider.GetByCoords(ctx.Context(), prayer.Coordinates{
			Latitude:  legacyLocation.Latitude,
			Longitude: legacyLocation.Longitude,
		})
		if err != nil {
			return fmt.Errorf("failed to fetch prayer times for location_id: %w", err)
		}

		location := result.Location
		location.ID = legacyLocation.ID
		if strings.TrimSpace(legacyLocation.Timezone) != "" {
			location.Timezone = legacyLocation.Timezone
		}

		mapped, err := mapPrayerTimesForLegacyResponse(result.Times, location)
		if err != nil {
			return fmt.Errorf("failed to map legacy prayer times response: %w", err)
		}

		ctx.Response().Header.Set(fiber.HeaderCacheControl, "max-age=86400")
		return ctx.JSON(mapped)
	})

	app.Use("/", static.New("", static.Config{FS: templates.FS()}))

	return app
}

type prayerTimesResponse struct {
	Date      string `json:"date"`
	DateHijri string `json:"date_hijri"`
	Fajr      string `json:"fajr"`
	Sunrise   string `json:"sunrise"`
	Dhuhr     string `json:"dhuhr"`
	Asr       string `json:"asr"`
	Sunset    string `json:"sunset,omitempty"`
	Maghrib   string `json:"maghrib"`
	Isha      string `json:"isha"`
}

func mapPrayerTimesForResponse(times []prayer.Times, location prayer.Location, utc bool) ([]any, error) {
	if utc {
		result := make([]any, 0, len(times))
		for _, item := range times {
			dateHijri := item.DateHijri
			if dateHijri == "" {
				dateHijri = hijricalendar.ToISODate(item.Date)
			}

			result = append(result, prayer.Times{
				Date:      item.Date.UTC(),
				DateHijri: dateHijri,
				Fajr:      item.Fajr.UTC(),
				Sunrise:   item.Sunrise.UTC(),
				Dhuhr:     item.Dhuhr.UTC(),
				Asr:       item.Asr.UTC(),
				Sunset:    item.Sunset.UTC(),
				Maghrib:   item.Maghrib.UTC(),
				Isha:      item.Isha.UTC(),
			})
		}
		return result, nil
	}

	tz := time.UTC
	if strings.TrimSpace(location.Timezone) != "" {
		loadedTZ, err := loadTimezone(location.Timezone)
		if err != nil {
			return nil, fmt.Errorf("failed to load location timezone: %w", err)
		}
		tz = loadedTZ
	}

	result := make([]any, 0, len(times))
	for _, item := range times {
		dateHijri := item.DateHijri
		if dateHijri == "" {
			dateHijri = hijricalendar.ToISODate(item.Date)
		}

		result = append(result, prayerTimesResponse{
			Date:      item.Date.In(tz).Format(time.DateOnly),
			DateHijri: dateHijri,
			Fajr:      formatHHMM(item.Fajr, tz),
			Sunrise:   formatHHMM(item.Sunrise, tz),
			Dhuhr:     formatHHMM(item.Dhuhr, tz),
			Asr:       formatHHMM(item.Asr, tz),
			Sunset:    formatHHMM(item.Sunset, tz),
			Maghrib:   formatHHMM(item.Maghrib, tz),
			Isha:      formatHHMM(item.Isha, tz),
		})
	}

	return result, nil
}

func formatHHMM(value time.Time, tz *time.Location) string {
	if value.IsZero() {
		return ""
	}
	return value.In(tz).Format("15:04")
}

func loadTimezone(name string) (*time.Location, error) {
	if strings.HasPrefix(name, "UTC") {
		offsetText := strings.TrimPrefix(name, "UTC")
		if offsetText == "" {
			return time.UTC, nil
		}

		offsetHours, err := strconv.Atoi(offsetText)
		if err != nil {
			return nil, fmt.Errorf("failed to parse utc offset timezone: %w", err)
		}
		return time.FixedZone(name, offsetHours*3600), nil
	}

	loc, err := time.LoadLocation(name)
	if err != nil {
		return nil, fmt.Errorf("failed to load iana timezone: %w", err)
	}

	return loc, nil
}

func mapPrayerTimesForLegacyResponse(times []prayer.Times, location prayer.Location) ([]fiber.Map, error) {
	tz := time.UTC
	if strings.TrimSpace(location.Timezone) != "" {
		loadedTZ, err := loadTimezone(location.Timezone)
		if err != nil {
			return nil, fmt.Errorf("failed to load location timezone: %w", err)
		}
		tz = loadedTZ
	}

	out := make([]fiber.Map, 0, len(times))
	for _, item := range times {
		out = append(out, fiber.Map{
			"date":    item.Date.In(tz).Format(time.RFC3339),
			"fajr":    formatHHMM(item.Fajr, tz),
			"sun":     formatHHMM(item.Sunrise, tz),
			"dhuhr":   formatHHMM(item.Dhuhr, tz),
			"asr":     formatHHMM(item.Asr, tz),
			"maghrib": formatHHMM(item.Maghrib, tz),
			"isha":    formatHHMM(item.Isha, tz),
		})
	}

	return out, nil
}

func respondDeprecatedEndpoint(ctx fiber.Ctx, replacementPath string) error {
	setDeprecationHeaders(ctx, replacementPath)

	return ctx.Status(http.StatusGone).JSON(httpError{
		Message: "This endpoint has been removed. Use " + replacementPath,
	})
}

func setDeprecationHeaders(ctx fiber.Ctx, replacementPath string) {
	ctx.Response().Header.Set("Deprecation", "true")
	ctx.Response().Header.Set("Sunset", "Wed, 30 Sep 2026 23:59:59 GMT")
	ctx.Response().Header.Set("Link", "<"+replacementPath+">; rel=\"successor-version\"")
}