//
//  SchemaMigratorTests.swift
//
//  Copyright 2026 Brendan Szymanski <hello@bscubed.dev>
//
//  This program is free software: you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation, either version 3 of the License, or
//  (at your option) any later version.
//
//  This program is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU General Public License for more details.
//
//  You should have received a copy of the GNU General Public License
//  along with this program.  If not, see <https://www.gnu.org/licenses/>.
//
//  SPDX-License-Identifier: GPL-3.0-or-later
//

import Foundation
import Testing

@testable import LuminateCore
@testable import LuminateStore

@Suite struct SchemaMigratorTests {
    @Test("Migrating a current database is a no-op")
    func currentDatabase() throws {
        let (url, directory) = makeDatabaseURL()
        defer { try? FileManager.default.removeItem(at: directory) }

        let database = try SQLiteDatabase(url: url)
        try SchemaMigrator.migrate(database)
        let snapshot = try SQLitePreferenceStore(url: url).initialSnapshot
        try SchemaMigrator.migrate(database)
        #expect(try database.userVersion == SchemaMigrator.latestVersion)
        #expect(try SQLitePreferenceStore(url: url).initialSnapshot == snapshot)
    }

    @Test("A newer minimum reader version rejects the database")
    func newerReaderVersion() throws {
        let (url, directory) = makeDatabaseURL()
        defer { try? FileManager.default.removeItem(at: directory) }

        let database = try SQLiteDatabase(url: url)
        try SchemaMigrator.migrate(database)
        try database.exec(
            "UPDATE schema_metadata SET minimum_reader_version = \(SchemaMigrator.latestVersion + 1);"
        )

        do {
            _ = try SQLitePreferenceStore(url: url)
            Issue.record("Expected a newer-reader migration error")
        } catch let error as PreferenceStoreError {
            #expect(
                error
                    == .requiresNewerApplication(
                        minimumReaderVersion: SchemaMigrator.latestVersion + 1,
                        supportedVersion: SchemaMigrator.latestVersion
                    )
            )
        }
    }

    @Test("A non-Luminate application identifier is rejected")
    func foreignApplication() throws {
        let (url, directory) = makeDatabaseURL()
        defer { try? FileManager.default.removeItem(at: directory) }

        let database = try SQLiteDatabase(url: url)
        try database.setApplicationID(1234)

        do {
            try SchemaMigrator.migrate(database)
            Issue.record("Expected a foreign-database error")
        } catch let error as PreferenceStoreError {
            #expect(error == .notALuminateDatabase(applicationID: 1234))
        }
    }

    @Test("A higher compatible schema version remains readable")
    func compatibleHigherVersion() throws {
        let (url, directory) = makeDatabaseURL()
        defer { try? FileManager.default.removeItem(at: directory) }

        let database = try SQLiteDatabase(url: url)
        try SchemaMigrator.migrate(database)
        try database.setUserVersion(SchemaMigrator.latestVersion + 1)
        let statement = try SQLiteStatement(
            database: database,
            sql: "INSERT INTO preference (key, value) VALUES (?1, ?2);"
        )
        try statement.bind(1, text: "server.url")
        try statement.bind(2, .text("http://compatible"))
        _ = try statement.step()

        let store = try SQLitePreferenceStore(url: url)
        #expect(store.initialSnapshot["server.url"] == .text("http://compatible"))
    }

    @Test("A failed migration rolls back its statements and version")
    func failedMigrationRollsBack() throws {
        let (url, directory) = makeDatabaseURL()
        defer { try? FileManager.default.removeItem(at: directory) }

        let database = try SQLiteDatabase(url: url)
        let failingMigration = StoreMigration(
            version: 2,
            name: "failing migration",
            minimumReaderVersion: 1,
            statements: [
                "CREATE TABLE version_two_marker (id INTEGER);",
                "CREATE TABLE preference (x);",
            ]
        )

        #expect(throws: PreferenceStoreError.self) {
            try SchemaMigrator.migrate(database, migrations: SchemaMigrator.migrations + [failingMigration])
        }
        #expect(try database.userVersion == 1)
        #expect(try tableExists("version_two_marker", in: database) == false)
    }

    @Test("Migration versions must be strictly increasing")
    func rejectsMalformedMigrationOrder() throws {
        let (url, directory) = makeDatabaseURL()
        defer { try? FileManager.default.removeItem(at: directory) }

        let database = try SQLiteDatabase(url: url)
        let migrations = [
            StoreMigration(version: 2, name: "second", minimumReaderVersion: 1, statements: []),
            StoreMigration(version: 1, name: "first", minimumReaderVersion: 1, statements: []),
        ]

        #expect(throws: PreferenceStoreError.malformedMigrationList(version: 1)) {
            try SchemaMigrator.migrate(database, migrations: migrations)
        }
    }

    /// Checks whether SQLite exposes a table with the requested name.
    private func tableExists(_ name: String, in database: SQLiteDatabase) throws -> Bool {
        let statement = try SQLiteStatement(
            database: database,
            sql: "SELECT name FROM sqlite_master WHERE type = 'table' AND name = ?1;"
        )
        try statement.bind(1, text: name)
        return try statement.step()
    }

    private func makeDatabaseURL() -> (URL, URL) {
        let directory = FileManager.default.temporaryDirectory
            .appending(path: "luminate-schema-\(UUID().uuidString)", directoryHint: .isDirectory)
        return (directory.appending(path: "preferences.sqlite"), directory)
    }
}