package repository

import (
	"context"
	"fmt"
)

// Notification delivery channels (notification_prefs.channel values).
const (
	ChannelInApp = "in_app"
	ChannelEmail = "email"
	ChannelPush  = "push"
)

// PrefKey is the lookup key for a (kind, channel) cell in a DisabledSet.
func PrefKey(kind, channel string) string { return kind + "/" + channel }

// NotificationPrefsRepo stores per-user notification opt-outs: one row per
// (kind, channel) the user has turned OFF. Absence of a row means enabled,
// so the table only ever holds overrides and new kinds/channels default on.
type NotificationPrefsRepo struct{ pg *Postgres }

func NewNotificationPrefsRepo(pg *Postgres) *NotificationPrefsRepo {
	return &NotificationPrefsRepo{pg: pg}
}

// DisabledSet returns the user's opt-outs keyed by PrefKey(kind, channel).
func (r *NotificationPrefsRepo) DisabledSet(ctx context.Context, userID string) (map[string]struct{}, error) {
	rows, err := r.pg.Pool.Query(ctx, `
		SELECT kind, channel FROM notification_prefs
		WHERE user_id = $1 AND enabled = FALSE`, userID)
	if err != nil {
		return nil, fmt.Errorf("list notification prefs: %w", err)
	}
	defer rows.Close()
	out := map[string]struct{}{}
	for rows.Next() {
		var kind, channel string
		if err := rows.Scan(&kind, &channel); err != nil {
			return nil, fmt.Errorf("scan notification pref: %w", err)
		}
		out[PrefKey(kind, channel)] = struct{}{}
	}
	return out, rows.Err()
}

// Disable records opt-out rows for every kind × channel pair.
func (r *NotificationPrefsRepo) Disable(ctx context.Context, userID string, kinds, channels []string) error {
	_, err := r.pg.Pool.Exec(ctx, `
		INSERT INTO notification_prefs (user_id, kind, channel, enabled)
		SELECT $1, k, c, FALSE
		FROM unnest($2::text[]) AS k, unnest($3::text[]) AS c
		ON CONFLICT (user_id, kind, channel)
		    DO UPDATE SET enabled = FALSE, updated_at = now()`,
		userID, kinds, channels)
	if err != nil {
		return fmt.Errorf("disable notification prefs: %w", err)
	}
	return nil
}

// Enable removes opt-out rows (absence = enabled) for every kind × channel
// pair.
func (r *NotificationPrefsRepo) Enable(ctx context.Context, userID string, kinds, channels []string) error {
	_, err := r.pg.Pool.Exec(ctx, `
		DELETE FROM notification_prefs
		WHERE user_id = $1 AND kind = ANY($2::text[]) AND channel = ANY($3::text[])`,
		userID, kinds, channels)
	if err != nil {
		return fmt.Errorf("enable notification prefs: %w", err)
	}
	return nil
}

// SyncLegacyColumns recomputes users.like_emails_enabled and
// users.sadhna_reminders_enabled from the prefs table, so an old frontend
// (or a rollback) reading the legacy columns stays correct. Call after any
// prefs write; drop together with the columns once fully rolled out.
func (r *NotificationPrefsRepo) SyncLegacyColumns(ctx context.Context, userID string) error {
	_, err := r.pg.Pool.Exec(ctx, `
		UPDATE users SET
		    like_emails_enabled = NOT EXISTS (
		        SELECT 1 FROM notification_prefs np
		        WHERE np.user_id = users.id
		          AND np.kind = 'post_like' AND np.channel = 'email'
		          AND np.enabled = FALSE),
		    -- The legacy reminder toggle was all-or-nothing: it reads as OFF
		    -- only when every reminder kind × channel cell is opted out.
		    sadhna_reminders_enabled = (
		        SELECT count(*) FROM notification_prefs np
		        WHERE np.user_id = users.id
		          AND np.kind IN ('chant_reminder', 'quote_reminder', 'chant_incomplete_reminder')
		          AND np.enabled = FALSE) < 9
		WHERE id = $1`, userID)
	if err != nil {
		return fmt.Errorf("sync legacy notification prefs: %w", err)
	}
	return nil
}