using System;
using System.Data;
using System.Threading.Tasks;

namespace Database.Tenants
{
    public class DbSetup
    {
        private readonly IDbConnection _db;

        public DbSetup(IDbConnection db)
        {
            _db = db ?? throw new ArgumentNullException(nameof(db));
        }

        /// <summary>
        /// Creates the users table in the ptmain schema.
        /// </summary>
        public void CreateUsersTable()
        {
            ExecuteInTransaction(@"
                CREATE TABLE IF NOT EXISTS ptmain.users (
                    id SERIAL PRIMARY KEY,
                    email VARCHAR(256) NOT NULL UNIQUE,
                    password_hash VARCHAR(256) NOT NULL,
                    security_stamp VARCHAR(36) NOT NULL,
                    email_confirmed BOOLEAN NOT NULL DEFAULT FALSE,
                    access_failed_count INTEGER NOT NULL DEFAULT 0,
                    lockout_enabled BOOLEAN NOT NULL DEFAULT TRUE,
                    lockout_end TIMESTAMPTZ NULL,
                    is_active BOOLEAN NOT NULL DEFAULT TRUE,
                    created_at TIMESTAMPTZ NOT NULL DEFAULT CURRENT_TIMESTAMP,
                    last_login_at TIMESTAMPTZ NULL
                );");
        }

        /// <summary>
        /// Creates the tenants table in the ptmain schema.
        /// </summary>
        public void CreateTenantsTable()
        {
            ExecuteInTransaction(@"
                CREATE TABLE IF NOT EXISTS ptmain.tenants (
                    id SERIAL PRIMARY KEY,
                    connection_string VARCHAR(500) NOT NULL,
                    is_active BOOLEAN NOT NULL DEFAULT TRUE,
                    created_by INTEGER NOT NULL REFERENCES ptmain.users(id),
                    created_at TIMESTAMPTZ NOT NULL DEFAULT CURRENT_TIMESTAMP
                );");
        }

        /// <summary>
        /// Creates the user_tenants table in the ptmain schema.
        /// </summary>
        public void CreateUserTenantsTable()
        {
            ExecuteInTransaction(@"
                CREATE TABLE IF NOT EXISTS ptmain.user_tenants (
                    user_id INTEGER NOT NULL REFERENCES ptmain.users(id),
                    tenant_id INTEGER NOT NULL REFERENCES ptmain.tenants(id),
                    pin_code VARCHAR(10) NULL,
                    created_at TIMESTAMPTZ NOT NULL DEFAULT CURRENT_TIMESTAMP,
                    PRIMARY KEY (user_id, tenant_id)
                );");
        }

        /// <summary>
        /// Sets up Row Level Security (RLS) for the tenants and user_tenants tables.
        /// </summary>
        public void SetupRLS()
        {
            ExecuteInTransaction(
                "ALTER TABLE ptmain.tenants ENABLE ROW LEVEL SECURITY;",
                "ALTER TABLE ptmain.user_tenants ENABLE ROW LEVEL SECURITY;",
                "DROP POLICY IF EXISTS tenant_access ON ptmain.tenants;",
                @"
                CREATE POLICY tenant_access ON ptmain.tenants
                    USING (id IN (
                        SELECT tenant_id 
                        FROM ptmain.user_tenants 
                        WHERE user_id = current_setting('app.user_id', TRUE)::INTEGER
                    ));",
                "DROP POLICY IF EXISTS user_tenant_access ON ptmain.user_tenants;",
                @"
                CREATE POLICY user_tenant_access ON ptmain.user_tenants
                    USING (user_id = current_setting('app.user_id', TRUE)::INTEGER);"
            );
        }

        /// <summary>
        /// Executes one or more SQL commands within a transaction.
        /// </summary>
        /// <param name="sqlCommands">The SQL commands to execute.</param>
        private void ExecuteInTransaction(params string[] sqlCommands)
        {
            if (_db.State != ConnectionState.Open)
                _db.Open();

            using var transaction = _db.BeginTransaction();
            try
            {
                foreach (var sql in sqlCommands)
                {
                    _db.ExecuteSql(sql, transaction: transaction);
                }
                transaction.Commit();
            }
            catch (Exception ex)
            {
                transaction.Rollback();
                throw new InvalidOperationException("Failed to execute SQL commands in transaction.", ex);
            }
        }
    }
}