gems/opal-task/internal/engine/database.go

package engine

import (
	"database/sql"
	"fmt"
	"os"

	_ "github.com/mattn/go-sqlite3"
)

var db *sql.DB

// InitDB initializes the database connection and runs migrations
func InitDB() error {
	if db != nil {
		return nil // Already initialized
	}

	dbPath, err := GetDBPath()
	if err != nil {
		return fmt.Errorf("failed to get database path: %w", err)
	}

	// Ensure data directory exists
	dataDir, err := GetDataDir()
	if err != nil {
		return fmt.Errorf("failed to get data directory: %w", err)
	}
	if err := os.MkdirAll(dataDir, 0755); err != nil {
		return fmt.Errorf("failed to create data directory: %w", err)
	}

	// Open database connection
	database, err := sql.Open("sqlite3", dbPath)
	if err != nil {
		return fmt.Errorf("failed to open database: %w", err)
	}

	// Enable foreign keys
	if _, err := database.Exec("PRAGMA foreign_keys = ON"); err != nil {
		return fmt.Errorf("failed to enable foreign keys: %w", err)
	}

	db = database

	// Run migrations
	if err := runMigrations(); err != nil {
		return fmt.Errorf("failed to run migrations: %w", err)
	}

	return nil
}

// GetDB returns the database connection
func GetDB() *sql.DB {
	return db
}

// CloseDB closes the database connection
func CloseDB() error {
	if db != nil {
		return db.Close()
	}
	return nil
}

// runMigrations runs database migrations
func runMigrations() error {
	// Create schema_version table if it doesn't exist
	_, err := db.Exec(`
		CREATE TABLE IF NOT EXISTS schema_version (
			version INTEGER PRIMARY KEY,
			applied_at INTEGER NOT NULL
		)
	`)
	if err != nil {
		return fmt.Errorf("failed to create schema_version table: %w", err)
	}

	// Get current schema version
	var currentVersion int
	err = db.QueryRow("SELECT COALESCE(MAX(version), 0) FROM schema_version").Scan(&currentVersion)
	if err != nil {
		return fmt.Errorf("failed to get current schema version: %w", err)
	}

	// Define migrations
	migrations := []struct {
		version int
		sql     string
	}{
		{
			version: 1,
			sql: `
				CREATE TABLE tasks (
					id INTEGER PRIMARY KEY AUTOINCREMENT,
					uuid TEXT UNIQUE NOT NULL,
					
					status INTEGER NOT NULL DEFAULT 80,
					description TEXT NOT NULL,
					project TEXT,
					priority INTEGER DEFAULT 1,
					
					created INTEGER NOT NULL,
					modified INTEGER NOT NULL,
					start INTEGER,
					end INTEGER,
					due INTEGER,
					scheduled INTEGER,
					wait INTEGER,
					until_date INTEGER,
					
					recurrence_duration INTEGER,
					parent_uuid TEXT,
					
					FOREIGN KEY (parent_uuid) REFERENCES tasks(uuid) ON DELETE CASCADE
				);

				CREATE INDEX idx_tasks_status ON tasks(status);
				CREATE INDEX idx_tasks_uuid ON tasks(uuid);
				CREATE INDEX idx_tasks_parent ON tasks(parent_uuid);
				CREATE INDEX idx_tasks_due ON tasks(due);
				CREATE INDEX idx_tasks_project ON tasks(project);

				CREATE TABLE tags (
					task_id INTEGER NOT NULL,
					tag TEXT NOT NULL,
					FOREIGN KEY (task_id) REFERENCES tasks(id) ON DELETE CASCADE,
					PRIMARY KEY (task_id, tag)
				);

				CREATE INDEX idx_tags_tag ON tags(tag);

				CREATE TABLE working_set (
					display_id INTEGER PRIMARY KEY,
					task_uuid TEXT NOT NULL,
					FOREIGN KEY (task_uuid) REFERENCES tasks(uuid) ON DELETE CASCADE
				);

				-- Users table (minimal for now, expandable later)
				CREATE TABLE users (
					id INTEGER PRIMARY KEY AUTOINCREMENT,
					username TEXT UNIQUE NOT NULL,
					email TEXT,
					oauth_subject TEXT UNIQUE,
					oauth_provider TEXT DEFAULT 'authentik',
					created_at INTEGER NOT NULL
				);

				-- Default shared user for household
				INSERT INTO users (id, username, created_at) VALUES (1, 'shared', unixepoch());

				-- API Keys for authentication
				CREATE TABLE api_keys (
					id INTEGER PRIMARY KEY AUTOINCREMENT,
					key TEXT UNIQUE NOT NULL,
					name TEXT NOT NULL,
					user_id INTEGER NOT NULL DEFAULT 1,
					created_at INTEGER NOT NULL,
					last_used INTEGER,
					revoked INTEGER DEFAULT 0,
					FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE
				);

				CREATE INDEX idx_api_keys_key ON api_keys(key);
				CREATE INDEX idx_api_keys_user ON api_keys(user_id);

				-- Sync state (per client device)
				CREATE TABLE sync_state (
					client_id TEXT PRIMARY KEY,
					last_sync INTEGER NOT NULL,
					last_change_id INTEGER DEFAULT 0
				);

				-- Change log (key:value format like edit command)
				CREATE TABLE change_log (
					id INTEGER PRIMARY KEY AUTOINCREMENT,
					task_uuid TEXT NOT NULL,
					change_type TEXT NOT NULL,
					changed_at INTEGER NOT NULL,
					data TEXT NOT NULL,
					FOREIGN KEY (task_uuid) REFERENCES tasks(uuid) ON DELETE CASCADE
				);

				CREATE INDEX idx_change_log_timestamp ON change_log(changed_at);
				CREATE INDEX idx_change_log_task ON change_log(task_uuid);
				CREATE INDEX idx_change_log_id ON change_log(id);

				-- Sync configuration
				CREATE TABLE sync_config (
					key TEXT PRIMARY KEY,
					value TEXT NOT NULL
				);

				-- Default: keep change log for 30 days
				INSERT INTO sync_config (key, value) VALUES ('change_log_retention_days', '30');

				-- Refresh tokens for OAuth
				CREATE TABLE refresh_tokens (
					id INTEGER PRIMARY KEY AUTOINCREMENT,
					user_id INTEGER NOT NULL,
					token_hash TEXT UNIQUE NOT NULL,
					expires_at INTEGER NOT NULL,
					created_at INTEGER NOT NULL,
					revoked INTEGER DEFAULT 0,
					FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE
				);

				CREATE INDEX idx_refresh_tokens_hash ON refresh_tokens(token_hash);
				CREATE INDEX idx_refresh_tokens_user ON refresh_tokens(user_id);

				-- Triggers to populate change_log
				CREATE TRIGGER track_task_create AFTER INSERT ON tasks
				BEGIN
					INSERT INTO change_log (task_uuid, change_type, changed_at, data)
					VALUES (NEW.uuid, 'create', NEW.modified,
						'uuid: ' || NEW.uuid || CHAR(10) ||
						'description: ' || NEW.description || CHAR(10) ||
						'status: ' || CASE NEW.status 
							WHEN 80 THEN 'pending'
							WHEN 67 THEN 'completed'
							WHEN 68 THEN 'deleted'
							WHEN 82 THEN 'recurring'
							ELSE 'pending'
						END || CHAR(10) ||
						'priority: ' || CASE NEW.priority
							WHEN 0 THEN 'L'
							WHEN 1 THEN 'D'
							WHEN 2 THEN 'M'
							WHEN 3 THEN 'H'
							ELSE 'D'
						END || CHAR(10) ||
						CASE WHEN NEW.project IS NOT NULL THEN 'project: ' || NEW.project || CHAR(10) ELSE '' END ||
						'created: ' || NEW.created || CHAR(10) ||
						'modified: ' || NEW.modified || CHAR(10) ||
						CASE WHEN NEW.start IS NOT NULL THEN 'start: ' || NEW.start || CHAR(10) ELSE '' END ||
						CASE WHEN NEW.end IS NOT NULL THEN 'end: ' || NEW.end || CHAR(10) ELSE '' END ||
						CASE WHEN NEW.due IS NOT NULL THEN 'due: ' || NEW.due || CHAR(10) ELSE '' END ||
						CASE WHEN NEW.scheduled IS NOT NULL THEN 'scheduled: ' || NEW.scheduled || CHAR(10) ELSE '' END ||
						CASE WHEN NEW.wait IS NOT NULL THEN 'wait: ' || NEW.wait || CHAR(10) ELSE '' END ||
						CASE WHEN NEW.until_date IS NOT NULL THEN 'until: ' || NEW.until_date || CHAR(10) ELSE '' END ||
						CASE WHEN NEW.recurrence_duration IS NOT NULL THEN 'recurrence: ' || NEW.recurrence_duration || CHAR(10) ELSE '' END ||
						CASE WHEN NEW.parent_uuid IS NOT NULL THEN 'parent_uuid: ' || NEW.parent_uuid || CHAR(10) ELSE '' END ||
						(SELECT CASE WHEN COUNT(*) > 0 
							THEN 'tags: ' || GROUP_CONCAT(tag, ',') || CHAR(10)
							ELSE '' 
						END 
						FROM (SELECT tag FROM tags WHERE task_id = NEW.id ORDER BY tag))
					);
				END;

				CREATE TRIGGER track_task_update AFTER UPDATE ON tasks
				BEGIN
					INSERT INTO change_log (task_uuid, change_type, changed_at, data)
					VALUES (NEW.uuid, 'update', NEW.modified,
						'uuid: ' || NEW.uuid || CHAR(10) ||
						'description: ' || NEW.description || CHAR(10) ||
						'status: ' || CASE NEW.status 
							WHEN 80 THEN 'pending'
							WHEN 67 THEN 'completed'
							WHEN 68 THEN 'deleted'
							WHEN 82 THEN 'recurring'
							ELSE 'pending'
						END || CHAR(10) ||
						'priority: ' || CASE NEW.priority
							WHEN 0 THEN 'L'
							WHEN 1 THEN 'D'
							WHEN 2 THEN 'M'
							WHEN 3 THEN 'H'
							ELSE 'D'
						END || CHAR(10) ||
						CASE WHEN NEW.project IS NOT NULL THEN 'project: ' || NEW.project || CHAR(10) ELSE '' END ||
						'created: ' || NEW.created || CHAR(10) ||
						'modified: ' || NEW.modified || CHAR(10) ||
						CASE WHEN NEW.start IS NOT NULL THEN 'start: ' || NEW.start || CHAR(10) ELSE '' END ||
						CASE WHEN NEW.end IS NOT NULL THEN 'end: ' || NEW.end || CHAR(10) ELSE '' END ||
						CASE WHEN NEW.due IS NOT NULL THEN 'due: ' || NEW.due || CHAR(10) ELSE '' END ||
						CASE WHEN NEW.scheduled IS NOT NULL THEN 'scheduled: ' || NEW.scheduled || CHAR(10) ELSE '' END ||
						CASE WHEN NEW.wait IS NOT NULL THEN 'wait: ' || NEW.wait || CHAR(10) ELSE '' END ||
						CASE WHEN NEW.until_date IS NOT NULL THEN 'until: ' || NEW.until_date || CHAR(10) ELSE '' END ||
						CASE WHEN NEW.recurrence_duration IS NOT NULL THEN 'recurrence: ' || NEW.recurrence_duration || CHAR(10) ELSE '' END ||
						CASE WHEN NEW.parent_uuid IS NOT NULL THEN 'parent_uuid: ' || NEW.parent_uuid || CHAR(10) ELSE '' END ||
						(SELECT CASE WHEN COUNT(*) > 0 
							THEN 'tags: ' || GROUP_CONCAT(tag, ',') || CHAR(10)
							ELSE '' 
						END 
						FROM (SELECT tag FROM tags WHERE task_id = NEW.id ORDER BY tag))
					);
				END;

				CREATE TRIGGER track_task_delete AFTER DELETE ON tasks
				BEGIN
					INSERT INTO change_log (task_uuid, change_type, changed_at, data)
					VALUES (OLD.uuid, 'delete', unixepoch(), 'uuid: ' || OLD.uuid);
				END;
			`,
		},
	}

	// Apply pending migrations
	for _, migration := range migrations {
		if migration.version > currentVersion {
			tx, err := db.Begin()
			if err != nil {
				return fmt.Errorf("failed to begin transaction for migration %d: %w", migration.version, err)
			}

			// Execute migration SQL
			if _, err := tx.Exec(migration.sql); err != nil {
				tx.Rollback()
				return fmt.Errorf("failed to execute migration %d: %w", migration.version, err)
			}

			// Record migration
			if _, err := tx.Exec(
				"INSERT INTO schema_version (version, applied_at) VALUES (?, ?)",
				migration.version,
				getCurrentTimestamp(),
			); err != nil {
				tx.Rollback()
				return fmt.Errorf("failed to record migration %d: %w", migration.version, err)
			}

			if err := tx.Commit(); err != nil {
				return fmt.Errorf("failed to commit migration %d: %w", migration.version, err)
			}
		}
	}

	return nil
}

// getCurrentTimestamp returns the current Unix timestamp
func getCurrentTimestamp() int64 {
	return timeNow().Unix()
}

// GetCurrentTimestamp returns the current Unix timestamp (exported for API use)
func GetCurrentTimestamp() int64 {
	return getCurrentTimestamp()
}

// CleanupChangeLog removes old change log entries based on retention policy
func CleanupChangeLog() error {
	db := GetDB()
	if db == nil {
		return fmt.Errorf("database not initialized")
	}

	// Get retention days from config
	var retentionDays int
	err := db.QueryRow("SELECT value FROM sync_config WHERE key = 'change_log_retention_days'").Scan(&retentionDays)
	if err != nil {
		retentionDays = 30 // Default to 30 days if not found
	}

	// Calculate cutoff timestamp
	cutoffTime := timeNow().AddDate(0, 0, -retentionDays).Unix()

	// Delete old entries
	result, err := db.Exec("DELETE FROM change_log WHERE changed_at < ?", cutoffTime)
	if err != nil {
		return fmt.Errorf("failed to cleanup change log: %w", err)
	}

	rows, _ := result.RowsAffected()
	if rows > 0 {
		fmt.Printf("Cleaned up %d old change log entries\n", rows)
	}

	return nil
}

// GetChangeLogRetentionDays returns the configured retention period
func GetChangeLogRetentionDays() (int, error) {
	db := GetDB()
	if db == nil {
		return 0, fmt.Errorf("database not initialized")
	}

	var days int
	err := db.QueryRow("SELECT value FROM sync_config WHERE key = 'change_log_retention_days'").Scan(&days)
	if err != nil {
		return 30, nil // Default
	}

	return days, nil
}

// SetChangeLogRetentionDays sets the retention period
func SetChangeLogRetentionDays(days int) error {
	db := GetDB()
	if db == nil {
		return fmt.Errorf("database not initialized")
	}

	_, err := db.Exec("INSERT OR REPLACE INTO sync_config (key, value) VALUES ('change_log_retention_days', ?)", days)
	return err
}