/*
 * Copyright (c) 2025 SimcuTeam. All rights reserved.
 * 数据库上下文：连接管理 + 变更提交 + 查询物化。
 *
 * 对齐 EF Core 的用法：
 *   class AppDbContext <: DbContext {
 *       public init(datasource: Datasource) { super(datasource) }
 *   }
 *   let db = AppDbContext(ds)
 *   db.set<User>().add(user)
 *   db.saveChanges()
 *
 * 语义说明（v1，操作队列模式）：add/update/remove 只入队，
 * saveChanges 开启事务按入队顺序逐条执行；执行后清空队列。
 */

package simcu::orm.db

import std.collection.*
import std.database.sql.*
import std.fs.*
import std.reflect.*
import simcu::orm.cli.{CliContext, MigrationCli}
import simcu::orm.model.*
import simcu::orm.query.*
import simcu::orm.sql.*
import simcu::orm.tracking.*
import simcu::orm.migrations.{Migrator, Migration}

/**
 * 数据库上下文。
 *
 * 基于实例的 CLI 入口（对齐 EF Core）：
 *   main(args: Array<String>) {
 *       let db = DataContext("pgsql", "Host=..;Database=..;Username=..;Password=..")
 *       if (db.cli(args)) { return }   // `app orm <命令>` 时执行 CLI 并退出
 *       // 正常启动
 *   }
 * cli() 的模型来自实例的 DbSet 属性(反射收集)；迁移列表来自子类
 * override migrations()；连接/驱动来自构造参数。
 */
public open class DbContext <: CliContext {
    internal let datasource: Datasource
    internal let dialect: SqlDialect
    internal let tracker = ChangeTracker()
    private let _sets = HashMap<String, Any>()
    private var _driverName: String
    private var _connString: String

    public init(datasource: Datasource, dialect: SqlDialect) {
        this.datasource = datasource
        this.dialect = dialect
        this._driverName = ""
        this._connString = ""
    }

    public init(datasource: Datasource) {
        this(datasource, OpenGaussDialect())
    }

    /// 便捷构造：由连接字符串创建 Datasource（驱动构建收敛在 DatasourceFactory）
    public init(connStr: String, dialect: SqlDialect) {
        this(DatasourceFactory.create(connStr), dialect)
        this._driverName = DatasourceFactory.detectDriver(connStr, DatasourceFactory.DEFAULT_DRIVER)
        this._connString = connStr
    }

    public init(connStr: String) {
        this(connStr, OpenGaussDialect())
    }

    /// 便捷构造：显式指定驱动类型（如 "pgsql"）+ 连接字符串
    public init(driverName: String, connStr: String, dialect: SqlDialect) {
        this(DatasourceFactory.create(connStr, driverName), dialect)
        this._driverName = DatasourceFactory.normalizeDriverName(driverName)
        this._connString = connStr
    }

    public init(driverName: String, connStr: String) {
        this(driverName, connStr, OpenGaussDialect())
    }

    /// 应用提供的迁移列表（子类 override；由 CLI 维护的注册文件提供实例）。
    /// 默认空——add 生成迁移不依赖它，update/list/create 需要。
    public open func migrations(): ArrayList<Migration> {
        ArrayList()
    }

    /// CLI 入口：`<app> orm <命令>` 时执行迁移 CLI 并返回 true；否则返回 false（正常启动）。
    /// 模型从本实例的 DbSet 属性反射收集，连接/驱动/方言来自构造参数。
    public func cli(args: Array<String>): Bool {
        if (args.size == 0 || args[0] != "orm") {
            return false
        }
        let list = ArrayList<String>()
        for (i in 1..args.size) {
            list.add(args[i])
        }
        MigrationCli.runOn(this, list)
        true
    }

    /// 反射收集本实例所有 DbSet<T> 的模型（DataContext 的 DbSet 字段/prop 均可）
    public func getModels(): ArrayList<EntityModel> {
        let result = ArrayList<EntityModel>()
        let ti = TypeInfo.of(this)
        // prop（getter 形式）与 var 字段形式都要支持
        for (p in ti.instanceProperties) {
            if (p.typeInfo.name.startsWith("DbSet")) {
                let v = p.getValue(this)
                match (v as DbSetBase) {
                    case Some(ds) => result.add(ds.getModel())
                    case None => ()
                }
            }
        }
        for (v in ti.instanceVariables) {
            if (v.typeInfo.name.startsWith("DbSet")) {
                let value = v.getValue(this)
                match (value as DbSetBase) {
                    case Some(ds) => result.add(ds.getModel())
                    case None => ()
                }
            }
        }
        result
    }

    /// 驱动注册名（构造时归一化；Datasource 构造无连接串时为空）
    public func getDriverName(): String {
        _driverName
    }

    /// 原始连接字符串（Datasource 构造时为 ""）
    public func getConnString(): String {
        _connString
    }

    /// CliContext：主数据源
    public func getDatasource(): Datasource {
        datasource
    }

    /// CliContext：迁移列表（委托子类的 migrations()）
    public func getMigrations(): ArrayList<Migration> {
        migrations()
    }

    /// CliContext：seed 运行上下文 = 本 DataContext 实例（seed 的 run(ctx) 用它操作 ORM）
    public func getSeedContext(): Any {
        this
    }

    /// 系统库数据源（数据库存在性检查用）。
    /// 由连接串 + 驱动派生：Database=xxx 换成系统库名（pgsql → postgres，mysql → mysql）。
    /// 无连接串或驱动不支持（sqlite 无系统库）时返回 None。
    public func getAdminDatasource(): ?Datasource {
        if (_connString.isEmpty() || _driverName.isEmpty()) {
            return None
        }
        if (_driverName == "sqlite") {
            return None
        }
        let adminDb = if (_driverName == "mysql") { "mysql" } else { "postgres" }
        var result = ""
        for (seg in _connString.split(";")) {
            let t = seg.trimAscii()
            if (t.isEmpty()) {
                continue
            }
            if (t.toAsciiLower().startsWith("database=")) {
                result += "Database=${adminDb};"
            } else {
                result += t
                result += ";"
            }
        }
        Some(DatasourceFactory.create(result, _driverName))
    }

    /// CliContext：应用所有迁移（委托 migrate）
    public func migrateAll(migrations: ArrayList<Migration>): Int64 {
        migrate(migrations)
    }

    /// 获取实体的 DbSet（同一实体类型复用同一个 DbSet 实例）
    public func set<T>(): DbSet<T> {
        let key = TypeInfo.of<T>().toString()
        if (let Some(existing) <- _sets.get(key)) {
            return (existing as DbSet<T>).getOrThrow()
        }
        let ds = DbSet<T>(this, ModelCache.get<T>())
        _sets[key] = ds
        ds
    }

    /// 待提交的变更条数
    public func pendingCount(): Int64 {
        tracker.count()
    }

    /// 当前方言（子类/应用可读取）
    public func getDialect(): SqlDialect {
        dialect
    }

    /// 应用迁移（对齐 EF Core Database.Migrate），返回本次应用的数量
    public func migrate(migrations: ArrayList<Migration>): Int64 {
        Migrator(datasource, dialect).migrate(migrations)
    }

    /// 无参便捷版：应用子类 migrations() 提供的全部迁移（`db.migrate()` 即运行 update）
    public func migrate(): Int64 {
        migrate(migrations())
    }

    /// 确认当前连接串指向的数据库是否存在（连系统库查询，不建库）。
    /// 需带连接串构造（_connString 非空）；sqlite 文件库返回文件是否存在。
    public func databaseExists(): Bool {
        if (_connString.isEmpty()) {
            return false
        }
        if (_driverName == "sqlite") {
            return exists(Path(sqliteFilePath()))
        }
        let dbName = databaseNameFromConnString()
        if (dbName.isEmpty()) {
            return false
        }
        match (getAdminDatasource()) {
            case None => false
            case Some(admin) =>
                let conn = admin.connect()
                try {
                    let stmt = conn.prepareStatement(dialect.databaseExistsSql())
                    try {
                        stmt.set<Any>(0, dbName)
                        let rs = stmt.query()
                        rs.next()
                    } finally {
                        stmt.close()
                    }
                } finally {
                    conn.close()
                }
        }
    }

    /// 是否存在未应用的迁移（库未创建或历史表不存在视为有待应用迁移）
    public func hasPendingMigrations(): Bool {
        let list = migrations()
        if (list.size == 0) {
            return false
        }
        try {
            let migrator = Migrator(datasource, dialect)
            let applied = migrator.appliedMigrationIds()
            for (m in list) {
                if (!applied.contains(m.migrationId)) {
                    return true
                }
            }
            false
        } catch (_: Exception) {
            // 数据库/历史表不存在 → 有待应用迁移
            true
        }
    }

    /// 提交全部待处理变更（事务内按入队顺序执行），返回影响的实体数
    public func saveChanges(): Int64 {
        var count: Int64 = 0
        if (tracker.count() == 0) {
            return 0
        }
        let conn = datasource.connect()
        let tx = conn.createTransaction()
        tx.begin()
        try {
            for (entry in tracker.getEntries()) {
                match (entry.state) {
                    case EntityState.Added => count += insertOne(conn, entry)
                    case EntityState.Modified => count += updateOne(conn, entry)
                    case EntityState.Deleted => count += deleteOne(conn, entry)
                    case _ => ()
                }
            }
            tx.commit()
            tracker.clear()
            count
        } catch (e: Exception) {
            try {
                tx.rollback()
            } catch (_) {
                ()
            }
            throw e
        } finally {
            conn.close()
        }
    }

    internal func getTracker(): ChangeTracker {
        tracker
    }

    /// 执行查询并物化实体（query 层回调）
    internal func query<T>(model: EntityModel, sql: String, params: ArrayList<Any>): ArrayList<T> {
        let conn = datasource.connect()
        try {
            let stmt = conn.prepareStatement(sql)
            try {
                ParamBinder.bind(stmt, params)
                let rs = stmt.query()
                let list = ArrayList<T>()
                while (rs.next()) {
                    let instance = materialize(rs, model)
                    list.add((instance as T).getOrThrow())
                }
                list
            } finally {
                stmt.close()
            }
        } finally {
            conn.close()
        }
    }

    /// 执行 COUNT 查询（query 层回调）
    internal func count(sql: String, params: ArrayList<Any>): Int64 {
        let conn = datasource.connect()
        try {
            let stmt = conn.prepareStatement(sql)
            try {
                ParamBinder.bind(stmt, params)
                let rs = stmt.query()
                if (rs.next()) {
                    return rs.getOrNull<Int64>(0).getOrThrow()
                }
                0
            } finally {
                stmt.close()
            }
        } finally {
            conn.close()
        }
    }

    /// 结果集 → 实体实例（列顺序与 model.properties 一致）
    internal func materialize(rs: QueryResult, model: EntityModel): Any {
        let instance = model.createInstance()
        var i = 0
        for (p in model.properties) {
            let v = ValueReader.read(rs, i, p.fullTypeName())
            i += 1
            if (let Some(val) <- v) {
                model.setValue(instance, p, val)
            }
        }
        instance
    }

    private func insertOne(conn: Connection, entry: EntityEntry): Int64 {
        let model = modelOf(entry.entity)
        let insertCols = ArrayList<String>()
        let values = ArrayList<Any>()
        for (p in model.properties) {
            if (p.autoIncrement) {
                continue
            }
            var v = model.getValue(entry.entity, p)
            // 客户端生成主键（String）：为空则生成唯一串
            if (p.clientGenerated && isBlankString(v)) {
                v = GuidUtil.generate()
                model.setValue(entry.entity, p, v)
            }
            insertCols.add(p.columnName)
            values.add(v)
        }
        let kp = model.keyProperty.getOrThrow()
        let returning = kp.autoIncrement
        let sql = dialect.buildInsert(model.tableName, insertCols, kp.columnName, returning)
        let stmt = conn.prepareStatement(sql)
        try {
            ParamBinder.bind(stmt, values)
            if (returning) {
                let rs = stmt.query()
                if (rs.next()) {
                    let v = ValueReader.read(rs, 0, kp.fullTypeName())
                    if (let Some(kv) <- v) {
                        model.setKeyValue(entry.entity, kv)
                    }
                }
            } else {
                stmt.update()
            }
            1
        } finally {
            stmt.close()
        }
    }

    private func updateOne(conn: Connection, entry: EntityEntry): Int64 {
        let model = modelOf(entry.entity)
        let setCols = ArrayList<String>()
        let values = ArrayList<Any>()
        for (p in model.properties) {
            if (p.isKey) {
                continue
            }
            setCols.add(p.columnName)
            values.add(model.getValue(entry.entity, p))
        }
        let kp = model.keyProperty.getOrThrow()
        values.add(model.getKeyValue(entry.entity))
        let sql = dialect.buildUpdate(model.tableName, setCols, kp.columnName)
        let stmt = conn.prepareStatement(sql)
        try {
            ParamBinder.bind(stmt, values)
            stmt.update()
            1
        } finally {
            stmt.close()
        }
    }

    private func deleteOne(conn: Connection, entry: EntityEntry): Int64 {
        let model = modelOf(entry.entity)
        let kp = model.keyProperty.getOrThrow()
        let sql = dialect.buildDelete(model.tableName, kp.columnName)
        let stmt = conn.prepareStatement(sql)
        try {
            stmt.set<Any>(0, model.getKeyValue(entry.entity))
            stmt.update()
            1
        } finally {
            stmt.close()
        }
    }

    private func modelOf(entity: Any): EntityModel {
        ModelCache.getFor(TypeInfo.of(entity))
    }

    private static func isBlankString(v: Any): Bool {
        if (let s: String <- v) {
            return s.isEmpty()
        }
        false
    }

    /// 从连接串解析数据库名：
    ///   URL 格式（postgres://user:pass@host:port/dbname?params）→ 路径段（去 query）；
    ///   ADO 风格（Host=..;Database=xxx;..）→ Database 值。
    /// 解析不到返回 ""。
    private func databaseNameFromConnString(): String {
        if (_connString.contains("://")) {
            let afterScheme = _connString.indexOf("://").getOrThrow() + 3
            let rest = _connString[afterScheme..]
            if (let Some(slash) <- rest.indexOf("/")) {
                var path = rest[slash + 1..]
                if (let Some(q) <- path.indexOf("?")) {
                    path = path[..q]
                }
                return path
            }
            return ""
        }
        for (seg in _connString.split(";")) {
            let t = seg.trimAscii()
            if (t.toAsciiLower().startsWith("database=")) {
                return t[t.indexOf("=").getOrThrow() + 1..]
            }
        }
        ""
    }

    /// sqlite 连接串 → 数据库文件路径（去 sqlite:// 前缀与 query 参数）
    private func sqliteFilePath(): String {
        var p = _connString
        if (p.startsWith("sqlite://")) {
            p = p[9..]
        } else if (p.startsWith("sqlite:")) {
            p = p[7..]
        }
        if (let Some(q) <- p.indexOf("?")) {
            p = p[..q]
        }
        p
    }
}

/**
 * DbSet 的非泛型访问基类：供 ORM CLI 通过反射拿到模型（EntityModel）。
 */
public abstract class DbSetBase {
    public func getModel(): EntityModel
}

/**
 * 实体的数据集（对齐 EF Core DbSet）。
 */
public class DbSet<T> <: DbSetBase {
    private let _context: DbContext
    private let _model: EntityModel
    private let _tracker: ChangeTracker

    public init(context: DbContext, model: EntityModel) {
        this._context = context
        this._model = model
        this._tracker = context.getTracker()
    }

    public override func getModel(): EntityModel {
        _model
    }

    /// 入队新增
    public func add(entity: T): Unit {
        _tracker.add(entity, EntityState.Added)
    }

    /// 入队修改（UPDATE 全部非主键列）
    public func update(entity: T): Unit {
        _tracker.add(entity, EntityState.Modified)
    }

    /// 入队删除
    public func remove(entity: T): Unit {
        _tracker.add(entity, EntityState.Deleted)
    }

    /// 构建查询
    public func query(): QueryBuilder<T> {
        QueryBuilder<T>(_model, _context.getDialect(),
            { sql, params => _context.query<T>(_model, sql, params) },
            { sql, params => _context.count(sql, params) })
    }

    /// 按主键查询（无结果返回 None）
    public func find(key: Any): ?T {
        let kp = _model.keyProperty.getOrThrow()
        let list = query().filter(kp.columnName, "=", key).take(1).toList()
        if (list.size > 0) {
            return Some(list[0])
        }
        None
    }

    /// 全表查询
    public func toList(): ArrayList<T> {
        query().toList()
    }

    /// 全表计数
    public func count(): Int64 {
        query().count()
    }
}