package db

import (
	"database/sql"
	"errors"
	"fmt"
	"strings"
)

// ICSSubscription is a user-added read-only calendar backed by a remote
// ICS/webcal URL, exposed alongside real calendars under
// "/cal/home/<name>/" (see internal/caldav/ics.go).
type ICSSubscription struct {
	Name  string
	URL   string
	Color string
}

// CreateICSSubscription registers a new ICS subscription owned by owner.
// Returns ErrReservedName if name is reserved for a computed calendar (see
// reservedCalendarNames), or ErrResourceExists if name is already used by
// one of owner's calendars or ICS subscriptions.
func (d *DB) CreateICSSubscription(owner, name, url, color string) error {
	if reservedCalendarNames[strings.ToLower(name)] {
		return ErrReservedName
	}
	// Shares the "/cal/home/<name>/" namespace with real calendars, so
	// reject a name already taken by one of those.
	var calExists int
	if err := d.conn.QueryRow(`SELECT COUNT(*) FROM calendars WHERE owner = ? AND name = ?`, owner, name).Scan(&calExists); err != nil {
		return fmt.Errorf("checking calendar name: %w", err)
	}
	if calExists > 0 {
		return ErrResourceExists
	}
	_, err := d.conn.Exec(`INSERT INTO ics_subscriptions (owner, name, url, color) VALUES (?, ?, ?, ?)`, owner, name, url, color)
	if err != nil {
		if isUniqueConstraintErr(err) {
			return ErrResourceExists
		}
		return fmt.Errorf("creating ics subscription: %w", err)
	}
	return nil
}

// DeleteICSSubscription removes an ICS subscription. Returns
// ErrResourceNotFound if it doesn't exist.
func (d *DB) DeleteICSSubscription(owner, name string) error {
	res, err := d.conn.Exec(`DELETE FROM ics_subscriptions WHERE owner = ? AND name = ?`, owner, name)
	if err != nil {
		return fmt.Errorf("deleting ics subscription: %w", err)
	}
	return requireRowsAffected(res, ErrResourceNotFound)
}

// SetICSSubscriptionColor updates an ICS subscription's display color.
// Returns ErrResourceNotFound if it doesn't exist.
func (d *DB) SetICSSubscriptionColor(owner, name, color string) error {
	res, err := d.conn.Exec(`UPDATE ics_subscriptions SET color = ? WHERE owner = ? AND name = ?`, color, owner, name)
	if err != nil {
		return fmt.Errorf("setting ics subscription color: %w", err)
	}
	return requireRowsAffected(res, ErrResourceNotFound)
}

// GetICSSubscription returns owner's ICS subscription registered under
// name. Returns ErrResourceNotFound if it doesn't exist.
func (d *DB) GetICSSubscription(owner, name string) (ICSSubscription, error) {
	sub := ICSSubscription{Name: name}
	err := d.conn.QueryRow(`SELECT url, color FROM ics_subscriptions WHERE owner = ? AND name = ?`, owner, name).Scan(&sub.URL, &sub.Color)
	if errors.Is(err, sql.ErrNoRows) {
		return ICSSubscription{}, ErrResourceNotFound
	}
	if err != nil {
		return ICSSubscription{}, fmt.Errorf("getting ics subscription: %w", err)
	}
	return sub, nil
}

// ListICSSubscriptions returns all of owner's ICS subscriptions, sorted by
// name.
func (d *DB) ListICSSubscriptions(owner string) ([]ICSSubscription, error) {
	rows, err := d.conn.Query(`SELECT name, url, color FROM ics_subscriptions WHERE owner = ? ORDER BY name`, owner)
	if err != nil {
		return nil, fmt.Errorf("listing ics subscriptions: %w", err)
	}
	defer rows.Close()

	var subs []ICSSubscription
	for rows.Next() {
		var s ICSSubscription
		if err := rows.Scan(&s.Name, &s.URL, &s.Color); err != nil {
			return nil, fmt.Errorf("scanning ics subscription: %w", err)
		}
		subs = append(subs, s)
	}
	return subs, rows.Err()
}