package notifications

import (
	"context"
	"errors"
	"fmt"
	"time"

	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
)

// EmailSettings are the digest's two knobs, in admin Settings (rule 25).
type EmailSettings struct {
	// SummaryHour is the local hour (0-23, in each user's own timezone) the
	// daily new-music summary goes out.
	SummaryHour int32
	// BatchWindowMinutes is how long a batch stays open after its first item.
	BatchWindowMinutes int32
}

const (
	minBatchWindowMinutes = 15
	maxBatchWindowMinutes = 1440
)

// DefaultEmailSettings mirrors migration 0074's column defaults.
var DefaultEmailSettings = EmailSettings{SummaryHour: 9, BatchWindowMinutes: 60}

// ErrEmailSettingOutOfRange is a value migration 0074's CHECKs would reject,
// so the API answers 400 naming the field rather than a constraint violation.
var ErrEmailSettingOutOfRange = errors.New("notification email setting out of range")

// BatchWindow is BatchWindowMinutes as a duration.
func (s EmailSettings) BatchWindow() time.Duration {
	return time.Duration(s.BatchWindowMinutes) * time.Minute
}

// LoadEmailSettings reads the settings. A failed read returns the defaults
// with the error, so the digest keeps its shipped cadence rather than stopping.
func LoadEmailSettings(ctx context.Context, q *dbq.Queries) (EmailSettings, error) {
	row, err := q.GetNotificationEmailSettings(ctx)
	if err != nil {
		return DefaultEmailSettings, fmt.Errorf("notification email settings: load: %w", err)
	}
	return EmailSettings{SummaryHour: row.SummaryHour, BatchWindowMinutes: row.BatchWindowMinutes}, nil
}

// SaveEmailSettings validates and writes the settings, returning them as saved.
// The digest reads them on its next tick; nothing is cached.
func SaveEmailSettings(ctx context.Context, q *dbq.Queries, in EmailSettings) (EmailSettings, error) {
	switch {
	case in.SummaryHour < 0 || in.SummaryHour > 23:
		return EmailSettings{}, fmt.Errorf("%w: summary_hour must be 0-23", ErrEmailSettingOutOfRange)
	case in.BatchWindowMinutes < minBatchWindowMinutes || in.BatchWindowMinutes > maxBatchWindowMinutes:
		return EmailSettings{}, fmt.Errorf("%w: batch_window_minutes must be %d-%d",
			ErrEmailSettingOutOfRange, minBatchWindowMinutes, maxBatchWindowMinutes)
	}
	row, err := q.UpdateNotificationEmailSettings(ctx, dbq.UpdateNotificationEmailSettingsParams{
		SummaryHour:        in.SummaryHour,
		BatchWindowMinutes: in.BatchWindowMinutes,
	})
	if err != nil {
		return EmailSettings{}, fmt.Errorf("notification email settings: save: %w", err)
	}
	return EmailSettings{SummaryHour: row.SummaryHour, BatchWindowMinutes: row.BatchWindowMinutes}, nil
}