package treepath

import (
	"database/sql"

	"github.com/google/uuid"

	"git.gobha.me/xcaliber/chat-switchboard/database"
)

// UpdateCursor upserts the channel_cursors row for a user.
func UpdateCursor(channelID, userID, messageID string) error {
	if database.IsSQLite() {
		// SQLite: id TEXT PRIMARY KEY has no default generator; supply one.
		// Use excluded.active_leaf_id so ON CONFLICT works cleanly.
		_, err := database.DB.Exec(`
			INSERT INTO channel_cursors (id, channel_id, user_id, active_leaf_id)
			VALUES (?, ?, ?, ?)
			ON CONFLICT (channel_id, user_id) DO UPDATE SET
				active_leaf_id = excluded.active_leaf_id, updated_at = datetime('now')
		`, uuid.New().String(), channelID, userID, messageID)
		return err
	}
	// Postgres: id has DEFAULT gen_random_uuid(); $3 is referenced twice.
	_, err := database.DB.Exec(`
		INSERT INTO channel_cursors (channel_id, user_id, active_leaf_id)
		VALUES ($1, $2, $3)
		ON CONFLICT (channel_id, user_id) DO UPDATE SET
			active_leaf_id = $3, updated_at = NOW()
	`, channelID, userID, messageID)
	return err
}

// NextSiblingIndex returns the next sibling_index for a new child of parentID.
// For root messages (parentID is nil), counts existing roots in the channel.
func NextSiblingIndex(channelID string, parentID *string) int {
	var maxIdx sql.NullInt64
	if parentID == nil {
		database.DB.QueryRow(database.Q(`
			SELECT MAX(sibling_index) FROM messages
			WHERE channel_id = $1 AND parent_id IS NULL AND deleted_at IS NULL
		`), channelID).Scan(&maxIdx)
	} else {
		database.DB.QueryRow(database.Q(`
			SELECT MAX(sibling_index) FROM messages
			WHERE parent_id = $1 AND deleted_at IS NULL
		`), *parentID).Scan(&maxIdx)
	}
	if !maxIdx.Valid {
		return 0
	}
	return int(maxIdx.Int64) + 1
}