// Package masterdb provides the SQLite database for the mcp-master daemon.
// It stores the cluster-wide node registry, service placements, and edge routes.
// This is separate from the agent's registry (internal/registry/) because the
// master and agent have fundamentally different schemas.
package masterdb

import (
	"database/sql"
	"fmt"

	_ "modernc.org/sqlite"
)

// Open opens the master database at the given path and runs migrations.
func Open(path string) (*sql.DB, error) {
	db, err := sql.Open("sqlite", path)
	if err != nil {
		return nil, fmt.Errorf("open database: %w", err)
	}

	for _, pragma := range []string{
		"PRAGMA journal_mode = WAL",
		"PRAGMA foreign_keys = ON",
		"PRAGMA busy_timeout = 5000",
	} {
		if _, err := db.Exec(pragma); err != nil {
			_ = db.Close()
			return nil, fmt.Errorf("exec %q: %w", pragma, err)
		}
	}

	if err := migrate(db); err != nil {
		_ = db.Close()
		return nil, fmt.Errorf("migrate: %w", err)
	}

	return db, nil
}

func migrate(db *sql.DB) error {
	_, err := db.Exec(`
		CREATE TABLE IF NOT EXISTS schema_migrations (
			version INTEGER PRIMARY KEY,
			applied_at TEXT NOT NULL DEFAULT (datetime('now'))
		);
	`)
	if err != nil {
		return fmt.Errorf("create migrations table: %w", err)
	}

	for i, m := range migrations {
		version := i + 1
		var count int
		if err := db.QueryRow("SELECT COUNT(*) FROM schema_migrations WHERE version = ?", version).Scan(&count); err != nil {
			return fmt.Errorf("check migration %d: %w", version, err)
		}
		if count > 0 {
			continue
		}

		if _, err := db.Exec(m); err != nil {
			return fmt.Errorf("run migration %d: %w", version, err)
		}
		if _, err := db.Exec("INSERT INTO schema_migrations (version) VALUES (?)", version); err != nil {
			return fmt.Errorf("record migration %d: %w", version, err)
		}
	}

	return nil
}

var migrations = []string{
	// Migration 1: cluster state
	`
	CREATE TABLE IF NOT EXISTS nodes (
		name        TEXT PRIMARY KEY,
		address     TEXT NOT NULL,
		role        TEXT NOT NULL DEFAULT 'worker',
		arch        TEXT NOT NULL DEFAULT 'amd64',
		status      TEXT NOT NULL DEFAULT 'unknown',
		containers  INTEGER NOT NULL DEFAULT 0,
		last_heartbeat TEXT,
		created_at  TEXT NOT NULL DEFAULT (datetime('now')),
		updated_at  TEXT NOT NULL DEFAULT (datetime('now'))
	);

	CREATE TABLE IF NOT EXISTS placements (
		service_name TEXT PRIMARY KEY,
		node         TEXT NOT NULL REFERENCES nodes(name),
		tier         TEXT NOT NULL DEFAULT 'worker',
		deployed_at  TEXT NOT NULL DEFAULT (datetime('now'))
	);

	CREATE TABLE IF NOT EXISTS edge_routes (
		hostname         TEXT PRIMARY KEY,
		service_name     TEXT NOT NULL,
		edge_node        TEXT NOT NULL REFERENCES nodes(name),
		backend_hostname TEXT NOT NULL,
		backend_port     INTEGER NOT NULL,
		created_at       TEXT NOT NULL DEFAULT (datetime('now'))
	);

	CREATE INDEX IF NOT EXISTS idx_edge_routes_service
		ON edge_routes(service_name);
	`,
}