/*
 * Copyright (c) 2025 SimcuTeam. All rights reserved.
 * 查询构建器：条件/排序/分页 → SQL，委托执行回调物化结果。
 *
 * 解耦设计：QueryBuilder 不直接依赖 DbContext/驱动。
 * 构造时传入 执行回调 (sql, params) -> ArrayList<T>，由 DbContext 提供。
 */

package simcu::orm.query

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

/**
 * 分页结果。
 */
public class PagedResult<T> {
    /// 当前页数据
    public var items: ArrayList<T> = ArrayList()
    /// 满足条件的总条数
    public var total: Int64 = 0
    /// 页码（从 1 开始）
    public var page: Int64 = 1
    /// 每页条数
    public var pageSize: Int64 = 20

    public init() {}

    public init(items: ArrayList<T>, total: Int64, page: Int64, pageSize: Int64) {
        this.items = items
        this.total = total
        this.page = page
        this.pageSize = pageSize
    }

    /// 总页数
    public func totalPages(): Int64 {
        if (pageSize <= 0) {
            return 0
        }
        (total + pageSize - 1) / pageSize
    }
}

/**
 * 查询构建器（对齐 EF Core IQueryable 的常用子集）。
 */
public class QueryBuilder<T> {
    private let _model: EntityModel
    private let _dialect: ISqlDialect
    private let _executor: (String, ArrayList<Any>) -> ArrayList<T>
    private let _counter: (String, ArrayList<Any>) -> Int64

    private let _whereParts = ArrayList<String>()
    private let _params = ArrayList<Any>()
    private let _orderByParts = ArrayList<String>()
    private var _skip: Int64 = 0
    private var _take: Int64 = 0

    public init(model: EntityModel, dialect: ISqlDialect, executor: (String, ArrayList<Any>) -> ArrayList<T>,
        counter: (String, ArrayList<Any>) -> Int64) {
        this._model = model
        this._dialect = dialect
        this._executor = executor
        this._counter = counter
    }

    /// filter("age > ?", [18])：原始片段，参数按 ? 顺序；片段中请直接写数据库列名
    public func filter(condition: String, params: ArrayList<Any>): QueryBuilder<T> {
        _whereParts.add("(${condition})")
        for (p in params) {
            _params.add(p)
        }
        this
    }

    /// filter("age", ">", 18)：属性名/列名自动映射为列名
    public func filter(property: String, op: String, value: Any): QueryBuilder<T> {
        let col = _model.mapColumn(property)
        _whereParts.add("(${_dialect.quoteName(col)} ${op} ?)")
        _params.add(value)
        this
    }

    public func orderBy(property: String): QueryBuilder<T> {
        _orderByParts.add("${_dialect.quoteName(_model.mapColumn(property))} ASC")
        this
    }

    public func orderByDesc(property: String): QueryBuilder<T> {
        _orderByParts.add("${_dialect.quoteName(_model.mapColumn(property))} DESC")
        this
    }

    public func skip(n: Int64): QueryBuilder<T> {
        _skip = n
        this
    }

    public func take(n: Int64): QueryBuilder<T> {
        _take = n
        this
    }

    /// 执行查询，返回实体列表
    public func toList(): ArrayList<T> {
        _executor(buildSelectSql(), copyParams())
    }

    /// 返回第一条（无结果返回 None）
    public func first(): ?T {
        let saved = _take
        _take = 1
        let list = toList()
        _take = saved
        if (list.size > 0) {
            return Some(list[0])
        }
        None
    }

    /// 满足条件的总数
    public func count(): Int64 {
        let sql = _dialect.buildCount(_model.tableName, whereSql())
        _counter(sql, copyParams())
    }

    /// 分页（page 从 1 开始）
    public func page(page: Int64, pageSize: Int64): PagedResult<T> {
        let total = count()
        let savedSkip = _skip
        let savedTake = _take
        _skip = (page - 1) * pageSize
        _take = pageSize
        let items = toList()
        _skip = savedSkip
        _take = savedTake
        PagedResult<T>(items, total, page, pageSize)
    }

    private func buildSelectSql(): String {
        _dialect.buildSelect(_model.tableName, selectColumns(), whereSql(), orderBySql(), _skip, _take)
    }

    /// 物化列（与属性顺序一致，结果集按此索引读取）
    private func selectColumns(): ArrayList<String> {
        let cols = ArrayList<String>()
        for (p in _model.properties) {
            cols.add(p.columnName)
        }
        cols
    }

    private func whereSql(): String {
        var sb = StringBuilder()
        var first = true
        for (w in _whereParts) {
            if (!first) {
                sb.append(" AND ")
            }
            sb.append(w)
            first = false
        }
        sb.toString()
    }

    private func orderBySql(): String {
        var sb = StringBuilder()
        var first = true
        for (o in _orderByParts) {
            if (!first) {
                sb.append(", ")
            }
            sb.append(o)
            first = false
        }
        sb.toString()
    }

    private func copyParams(): ArrayList<Any> {
        let copy = ArrayList<Any>()
        for (p in _params) {
            copy.add(p)
        }
        copy
    }
}