/*
 * Copyright (c) 2025 SimcuTeam. All rights reserved.
 * 迁移基础设施：Migration 基类 + MigrationBuilder 声明式操作 + DDL SQL 生成。
 *
 * 用法（对齐 EF Core 迁移）：
 *   public class InitialCreate <: Migration {
 *       public init() { super("20250701000000_InitialCreate", "创建用户表") }
 *       public override func up(builder: MigrationBuilder): Unit {
 *           builder.createTable("users") { tb =>
 *               tb.column("id", ColumnTypes.BigIntCol).primary().autoInc().notNull()
 *               tb.column("name", ColumnTypes.TextCol).withMaxLength(100).notNull()
 *           }
 *           builder.createIndex("ix_users_name", "users", ["name"])
 *       }
 *       public override func down(builder: MigrationBuilder): Unit {
 *           builder.dropTable("users")
 *       }
 *   }
 */

package simcu::orm.migrations

import std.collection.*
import std.time.*
import simcu::orm.sql.*

/**
 * 列定义（表结构/迁移用）。列类型 ColumnTypes 定义于 simcu::orm.sql，DDL 映射由方言决定。
 */
public class ColumnDefinition {
    public var name: String = ""
    public var columnType: ColumnTypes = ColumnTypes.TextCol
    public var primaryKey: Bool = false
    public var autoIncrement: Bool = false
    public var nullable: Bool = true
    public var unique: Bool = false
    public var maxLength: Int64 = 255
    public var defaultValue: ?Any = None

    public init(name: String, columnType: ColumnTypes) {
        this.name = name
        this.columnType = columnType
    }

    /// 标记主键
    public func primary(): ColumnDefinition {
        this.primaryKey = true
        this
    }

    /// 标记自增（仅整型列有效）
    public func autoInc(): ColumnDefinition {
        this.autoIncrement = true
        this
    }

    /// 标记非空
    public func notNull(): ColumnDefinition {
        this.nullable = false
        this
    }

    /// 标记唯一
    public func withUnique(): ColumnDefinition {
        this.unique = true
        this
    }

    /// 指定字符串最大长度
    public func withMaxLength(n: Int64): ColumnDefinition {
        this.maxLength = n
        this
    }

    /// 指定默认值
    public func withDefault(value: Any): ColumnDefinition {
        this.defaultValue = Some(value)
        this
    }
}

/**
 * 迁移操作类型。
 */
public enum MigrationOperationKind {
    | CreateTable
    | DropTable
    | AddColumn
    | DropColumn
    | AlterColumn
    | RenameColumn
    | CreateIndex
    | DropIndex
    | RawSql
}

/**
 * 一条迁移操作（不同 kind 使用对应字段）。
 */
public class MigrationOperation {
    public let kind: MigrationOperationKind
    public var tableName: String = ""
    public var columnName: String = ""
    public var newColumnName: String = ""
    public var column: ?ColumnDefinition = None
    public var columnDefs: ArrayList<ColumnDefinition> = ArrayList()
    public var indexName: String = ""
    public var columnNames: ArrayList<String> = ArrayList()
    public var unique: Bool = false
    public var sql: String = ""

    public init(kind: MigrationOperationKind) {
        this.kind = kind
    }
}

/**
 * 建表辅助（createTable 的闭包参数）。
 */
public class TableBuilder {
    public let tableName: String
    internal let columns = ArrayList<ColumnDefinition>()

    public init(tableName: String) {
        this.tableName = tableName
    }

    /// 声明一列（返回列定义以支持链式标记）
    public func column(name: String, columnType: ColumnTypes): ColumnDefinition {
        let c = ColumnDefinition(name, columnType)
        columns.add(c)
        c
    }
}

/**
 * 迁移构建器：声明式累积操作（对齐 EF Core MigrationBuilder）。
 */
public class MigrationBuilder {
    internal let operations = ArrayList<MigrationOperation>()

    public init() {}

    /// 当前累积的操作列表（供执行器/测试读取）
    public func getOperations(): ArrayList<MigrationOperation> {
        operations
    }

    public func createTable(name: String, build: (TableBuilder) -> Unit): MigrationBuilder {
        let tb = TableBuilder(name)
        build(tb)
        let op = MigrationOperation(MigrationOperationKind.CreateTable)
        op.tableName = name
        op.columnDefs = tb.columns
        operations.add(op)
        this
    }

    public func dropTable(name: String): MigrationBuilder {
        let op = MigrationOperation(MigrationOperationKind.DropTable)
        op.tableName = name
        operations.add(op)
        this
    }

    public func addColumn(table: String, column: ColumnDefinition): MigrationBuilder {
        let op = MigrationOperation(MigrationOperationKind.AddColumn)
        op.tableName = table
        op.column = Some(column)
        operations.add(op)
        this
    }

    public func dropColumn(table: String, columnName: String): MigrationBuilder {
        let op = MigrationOperation(MigrationOperationKind.DropColumn)
        op.tableName = table
        op.columnName = columnName
        operations.add(op)
        this
    }

    public func alterColumn(table: String, column: ColumnDefinition): MigrationBuilder {
        let op = MigrationOperation(MigrationOperationKind.AlterColumn)
        op.tableName = table
        op.column = Some(column)
        operations.add(op)
        this
    }

    public func renameColumn(table: String, oldName: String, newName: String): MigrationBuilder {
        let op = MigrationOperation(MigrationOperationKind.RenameColumn)
        op.tableName = table
        op.columnName = oldName
        op.newColumnName = newName
        operations.add(op)
        this
    }

    public func createIndex(indexName: String, table: String, columns: ArrayList<String>): MigrationBuilder {
        createIndex(indexName, table, columns, false)
    }

    public func createIndex(indexName: String, table: String, columns: ArrayList<String>,
        unique: Bool): MigrationBuilder {
        let op = MigrationOperation(MigrationOperationKind.CreateIndex)
        op.indexName = indexName
        op.tableName = table
        op.columnNames = columns
        op.unique = unique
        operations.add(op)
        this
    }

    public func dropIndex(indexName: String, table: String): MigrationBuilder {
        let op = MigrationOperation(MigrationOperationKind.DropIndex)
        op.indexName = indexName
        op.tableName = table
        operations.add(op)
        this
    }

    public func rawSql(sql: String): MigrationBuilder {
        let op = MigrationOperation(MigrationOperationKind.RawSql)
        op.sql = sql
        operations.add(op)
        this
    }
}

/**
 * 迁移基类：migrationId 形如 "20250701000000_InitialCreate"（时间戳_名称），按字典序应用。
 * 两种使用方式：
 * 1. 子类 override up/down 手写声明式操作（MigrationBuilder）；
 * 2. 由 MigrationGenerator 从模型生成时注入 preset 操作，基类 up/down 自动重放。
 */
public open class Migration {
    public let migrationId: String
    public let description: String

    /// 由 MigrationGenerator 注入的 up 操作（按序执行）
    internal var presetOperations = ArrayList<MigrationOperation>()
    /// 由 MigrationGenerator 注入的 down 操作（按序执行，已按 up 逆序反转）
    internal var presetDownOperations = ArrayList<MigrationOperation>()

    public init(migrationId: String, description: String) {
        this.migrationId = migrationId
        this.description = description
    }

    public init(migrationId: String) {
        this.migrationId = migrationId
        this.description = ""
    }

    public open func up(builder: MigrationBuilder): Unit {
        for (op in presetOperations) {
            builder.operations.add(op)
        }
    }

    public open func down(builder: MigrationBuilder): Unit {
        for (op in presetDownOperations) {
            builder.operations.add(op)
        }
    }
}

/**
 * DDL SQL 工厂：MigrationOperation → SQL（类型映射与差异语法委托给 ISqlDialect）。
 */
public class DdlFactory {
    public init() {}

    public func toSql(op: MigrationOperation, dialect: ISqlDialect): String {
        match (op.kind) {
            case MigrationOperationKind.CreateTable => createTableSql(op, dialect)
            case MigrationOperationKind.DropTable => "DROP TABLE IF EXISTS ${dialect.quoteName(op.tableName)}"
            case MigrationOperationKind.AddColumn =>
                "ALTER TABLE ${dialect.quoteName(op.tableName)} ADD COLUMN ${columnDefSql(op.column.getOrThrow(), dialect)}"
            case MigrationOperationKind.DropColumn =>
                "ALTER TABLE ${dialect.quoteName(op.tableName)} DROP COLUMN ${dialect.quoteName(op.columnName)}"
            case MigrationOperationKind.AlterColumn =>
                dialect.buildAlterColumn(op.tableName, columnDefSql(op.column.getOrThrow(), dialect))
            case MigrationOperationKind.RenameColumn =>
                "ALTER TABLE ${dialect.quoteName(op.tableName)} RENAME COLUMN ${dialect.quoteName(op.columnName)} TO ${dialect.quoteName(op.newColumnName)}"
            case MigrationOperationKind.CreateIndex => createIndexSql(op, dialect)
            case MigrationOperationKind.DropIndex => dialect.buildDropIndex(op.indexName, op.tableName)
            case MigrationOperationKind.RawSql => op.sql
        }
    }

    /// 解析 AddColumn/AlterColumn 为可执行 SQL 列表（兼容"同名列修改数据结构"场景）：
    ///   - 库中无同名列 → 单条 ADD COLUMN
    ///   - 有同名列且类型一致 → AddColumn 幂等跳过（空列表）；AlterColumn 保留原 SQL（处理非空/长度等变化）
    ///   - 有同名列但类型不同 → 先 DROP COLUMN 再 ADD COLUMN（重建该字段）
    /// existingType 来自 information_schema.data_type；None 表示列不存在。
    public func resolveColumnSqls(op: MigrationOperation, dialect: ISqlDialect,
        existingType: ?String): ArrayList<String> {
        let result = ArrayList<String>()
        let col = op.column.getOrThrow()
        match (existingType) {
            case None => result.add(toSql(op, dialect))
            case Some(dbType) =>
                let target = dialect.columnTypeSql(col.columnType, col.autoIncrement, col.maxLength)
                if (normalizeTypeName(dbType) == normalizeTypeName(target)) {
                    // 类型一致：AddColumn 视为幂等跳过；AlterColumn 保留原 SQL
                    let isAlter = match (op.kind) {
                        case MigrationOperationKind.AlterColumn => true
                        case _ => false
                    }
                    if (isAlter) {
                        result.add(toSql(op, dialect))
                    }
                } else {
                    // 类型不同：先删除老字段，再新增新字段
                    let drop = MigrationOperation(MigrationOperationKind.DropColumn)
                    drop.tableName = op.tableName
                    drop.columnName = col.name
                    result.add(toSql(drop, dialect))
                    result.add(toSql(op, dialect))
                }
        }
        result
    }

    /// 类型名归一化：方言 SQL 类型 ↔ information_schema.data_type，统一为小写基础类型（忽略长度/精度括号）。
    public static func normalizeTypeName(t: String): String {
        let lower = asciiLower(t)
        let base = if (let Some(i) <- lower.indexOf("(")) { lower[0..i] } else { lower }
        match (base) {
            case "bigserial" | "bigint" | "int8" => "bigint"
            case "serial" | "integer" | "int" | "int4" => "integer"
            case "smallint" | "int2" => "smallint"
            case "varchar" | "character varying" => "varchar"
            case "character" | "char" | "bpchar" => "char"
            case "text" => "text"
            case "boolean" | "bool" => "boolean"
            case "double precision" | "float8" => "double precision"
            case "real" | "float4" => "real"
            case "timestamp" | "timestamp without time zone" | "timestamp with time zone" => "timestamp"
            case "decimal" | "numeric" => "decimal"
            case "bytea" => "bytea"
            case _ => base
        }
    }

    /// ASCII 大写转小写（A-Z → a-z，其余字符不变；仅依赖切片与 indexOf，避免 std String 缺失 API）
    private static func asciiLower(s: String): String {
        let upper = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
        let lower = "abcdefghijklmnopqrstuvwxyz"
        let sb = StringBuilder()
        for (i in 0..s.size) {
            let c = s[i..i + 1]
            if (let Some(idx) <- upper.indexOf(c)) {
                sb.append(lower[idx..idx + 1])
            } else {
                sb.append(c)
            }
        }
        sb.toString()
    }

    private func createTableSql(op: MigrationOperation, dialect: ISqlDialect): String {
        let sb = StringBuilder()
        sb.append("CREATE TABLE IF NOT EXISTS ${dialect.quoteName(op.tableName)} (\n")
        var first = true
        for (c in op.columnDefs) {
            if (!first) {
                sb.append(",\n")
            }
            sb.append("  ${columnDefSql(c, dialect)}")
            first = false
        }
        sb.append("\n)")
        sb.toString()
    }

    private func createIndexSql(op: MigrationOperation, dialect: ISqlDialect): String {
        let sb = StringBuilder()
        sb.append("CREATE ")
        if (op.unique) {
            sb.append("UNIQUE ")
        }
        sb.append("INDEX ${dialect.quoteName(op.indexName)} ON ${dialect.quoteName(op.tableName)} (")
        var first = true
        for (c in op.columnNames) {
            if (!first) {
                sb.append(", ")
            }
            sb.append(dialect.quoteName(c))
            first = false
        }
        sb.append(")")
        sb.toString()
    }

    private func columnDefSql(col: ColumnDefinition, dialect: ISqlDialect): String {
        let sb = StringBuilder()
        sb.append(dialect.quoteName(col.name))
        sb.append(" ${dialect.columnTypeSql(col.columnType, col.autoIncrement, col.maxLength)}")
        if (!col.nullable || col.primaryKey) {
            sb.append(" NOT NULL")
        }
        if (col.primaryKey) {
            sb.append(" PRIMARY KEY")
        }
        if (col.unique) {
            sb.append(" UNIQUE")
        }
        if (let Some(dv) <- col.defaultValue) {
            sb.append(" DEFAULT ${defaultValueSql(dv)}")
        }
        sb.toString()
    }

    private func defaultValueSql(v: Any): String {
        if (let s: String <- v) {
            return "'${escapeQuotes(s)}'"
        }
        if (let b: Bool <- v) {
            return if (b) { "TRUE" } else { "FALSE" }
        }
        if (let i64: Int64 <- v) {
            return "${i64}"
        }
        if (let i32: Int32 <- v) {
            return "${i32}"
        }
        if (let i16: Int16 <- v) {
            return "${i16}"
        }
        if (let i8: Int8 <- v) {
            return "${i8}"
        }
        if (let u64: UInt64 <- v) {
            return "${u64}"
        }
        if (let u32: UInt32 <- v) {
            return "${u32}"
        }
        if (let u16: UInt16 <- v) {
            return "${u16}"
        }
        if (let u8: UInt8 <- v) {
            return "${u8}"
        }
        if (let f64: Float64 <- v) {
            return "${f64}"
        }
        if (let f32: Float32 <- v) {
            return "${f32}"
        }
        if (let r: Rune <- v) {
            return "'${r}'"
        }
        if (let d: DateTime <- v) {
            return "'${d.toString()}'"
        }
        throw Exception("simorm: 不支持的默认值类型，请使用 String/Bool/数值/Rune/DateTime")
    }

    private func escapeQuotes(s: String): String {
        var sb = StringBuilder()
        for (c in s.runes()) {
            if (c == Rune(0x27)) {
                sb.append("''")
            } else {
                sb.append(c)
            }
        }
        sb.toString()
    }
}