/*
 * Copyright (c) 2025 SimcuTeam. All rights reserved.
 * JsonReader：JsonValue → 对象（全反射）。
 *
 * - 目标类型来自泛型 T（TypeInfo.of<T>()）
 * - 反序列化要求：无参构造 + var 字段（let 只读字段跳过）
 * - 类型不匹配做宽松转换（JsonInt/JsonFloat/JsonString 互转）
 */

package simapi_serialization.json

import std.collection.*
import std.convert.*
import std.reflect.*
import stdx.encoding.json.*

/**
 * JsonValue → 对象 读取器。
 */
public class JsonReader {
    private init() {}

    public static func read<T>(value: JsonValue, options: JsonOption): T {
        let result = readValue(value, TypeInfo.of<T>(), options, 0)
        if (let t: T <- result) {
            return t
        }
        throw Exception("JsonSerializer: 反序列化结果类型不匹配")
    }

    private static func readValue(value: JsonValue, typeInfo: TypeInfo, options: JsonOption, depth: Int64): Any {
        if (depth > options.maxDepth) {
            throw Exception("JsonSerializer: 超过最大递归深度 ${options.maxDepth}")
        }
        let typeName = typeInfo.toString()

        // 基本类型
        match (typeName) {
            case "String" => return readString(value)
            case "Bool" => return readBool(value)
            case "Int64" => return readInt64(value)
            case "Int32" => return Int32(readInt64(value))
            case "Int16" => return Int16(readInt64(value))
            case "Int8" => return Int8(readInt64(value))
            case "UInt8" => return UInt8(readInt64(value))
            case "UInt16" => return UInt16(readInt64(value))
            case "UInt32" => return UInt32(readInt64(value))
            case "UInt64" => return UInt64(readInt64(value))
            case "Float64" => return readFloat64(value)
            case "Float32" => return Float32(readFloat64(value))
            case "Rune" => return readChar(value)
            case _ => ()
        }

        // Option<X>：null → None；否则读取内层并用枚举构造器包 Some
        if (typeName.startsWith("Option<")) {
            if (value is JsonNull) {
                // 必须用目标类型 Option<X> 的 None 构造器创建，保证运行时类型匹配。
                // 反射层将 Option 构造器统一登记为 1 参数槽（None 的参数类型是内层 X），
                // 传一个 X 的占位值即可（None 构造器忽略实参语义）。
                if (let et: EnumTypeInfo <- typeInfo) {
                    let ctor = et.getConstructor("None", argsCount: 1)
                    let innerName = JsonWriter.extractTypeArgs(typeName)[0]
                    let placeholder = defaultValueFor(innerName)
                    return ctor.apply([placeholder])
                }
                return None
            }
            let innerName = JsonWriter.extractTypeArgs(typeName)[0]
            let innerVal = readValue(value, TypeInfo.get(innerName), options, depth + 1)
            if (let et: EnumTypeInfo <- typeInfo) {
                let ctor = et.getConstructor("Some", argsCount: 1)
                return ctor.apply([innerVal])
            }
            return Some(innerVal)
        }

        // 集合
        if (typeName.startsWith("Array<")) {
            let elemName = JsonWriter.extractTypeArgs(typeName)[0]
            return readArray(value, elemName, options, depth)
        }
        if (typeName.startsWith("std.collection.ArrayList<")) {
            let elemName = JsonWriter.extractTypeArgs(typeName)[0]
            return readArrayList(value, elemName, options, depth)
        }
        if (typeName.startsWith("std.collection.HashSet<")) {
            let elemName = JsonWriter.extractTypeArgs(typeName)[0]
            return readHashSet(value, elemName, options, depth)
        }
        if (typeName.startsWith("std.collection.HashMap<")) {
            let args = JsonWriter.extractTypeArgs(typeName)
            return readHashMap(value, args[0], args[1], options, depth)
        }

        // Any / Object → 通用读取
        if (typeName == "Any" || typeName == "Object") {
            return jsonToAny(value)
        }

        // 枚举：按构造器名创建
        if (let et: EnumTypeInfo <- typeInfo) {
            let name = readString(value)
            return et.construct(name, [])
        }

        // 对象：反射创建 + 赋值
        if (let ct: ClassTypeInfo <- typeInfo) {
            return readObject(value, ct, options, depth)
        }

        throw Exception("JsonSerializer: 不支持的目标类型 ${typeName}")
    }

    private static func readObject(value: JsonValue, ct: ClassTypeInfo, options: JsonOption, depth: Int64): Any {
        let instance = ct.construct([])
        let fields = ReflectionCache.getFields(ct, options)
        let jobj = value.asObject()
        for (f in fields) {
            if (f.ignore) {
                continue
            }
            if (!f.mutable) {
                continue
            }
            match (jobj.get(f.jsonName)) {
                case Some(jv) =>
                    if (jv is JsonNull) {
                        continue // null：跳过，保持字段默认值
                    }
                    let fieldVal = readValue(jv, f.typeInfo.getOrThrow(), options, depth + 1)
                    f.variable.getOrThrow().setValue(instance, fieldVal)
                case None => ()
            }
        }
        instance
    }

    /// Array<X>：经 ArrayList<X> 构造 + add + toArray
    private static func readArray(value: JsonValue, elemName: String, options: JsonOption, depth: Int64): Any {
        let listTypeName = "std.collection.ArrayList<${elemName}>"
        let listCt = (TypeInfo.get(listTypeName) as ClassTypeInfo) ?? throw Exception("JsonSerializer: 无法解析类型 ${listTypeName}")
        let list = listCt.construct([])
        let addFunc = listCt.getInstanceFunction("add", [TypeInfo.get(elemName)])
        let jarr = value.asArray()
        for (item in jarr.getItems()) {
            let elem = readValue(item, TypeInfo.get(elemName), options, depth + 1)
            addFunc.apply(list, [elem])
        }
        let toArrayFunc = listCt.getInstanceFunction("toArray", [])
        toArrayFunc.apply(list, [])
    }

    private static func readArrayList(value: JsonValue, elemName: String, options: JsonOption, depth: Int64): Any {
        let ct = (TypeInfo.get("std.collection.ArrayList<${elemName}>") as ClassTypeInfo) ?? throw Exception("JsonSerializer: 无法解析 ArrayList<${elemName}>")
        let list = ct.construct([])
        let addFunc = ct.getInstanceFunction("add", [TypeInfo.get(elemName)])
        let jarr = value.asArray()
        for (item in jarr.getItems()) {
            let elem = readValue(item, TypeInfo.get(elemName), options, depth + 1)
            addFunc.apply(list, [elem])
        }
        list
    }

    private static func readHashSet(value: JsonValue, elemName: String, options: JsonOption, depth: Int64): Any {
        let ct = (TypeInfo.get("std.collection.HashSet<${elemName}>") as ClassTypeInfo) ?? throw Exception("JsonSerializer: 无法解析 HashSet<${elemName}>")
        let set = ct.construct([])
        let addFunc = ct.getInstanceFunction("add", [TypeInfo.get(elemName)])
        let jarr = value.asArray()
        for (item in jarr.getItems()) {
            let elem = readValue(item, TypeInfo.get(elemName), options, depth + 1)
            addFunc.apply(set, [elem])
        }
        set
    }

    private static func readHashMap(value: JsonValue, keyName: String, valName: String, options: JsonOption,
        depth: Int64): Any {
        let ct = (TypeInfo.get("std.collection.HashMap<${keyName}, ${valName}>") as ClassTypeInfo) ?? throw Exception("JsonSerializer: 无法解析 HashMap<${keyName}, ${valName}>")
        let map = ct.construct([])
        let addFunc = ct.getInstanceFunction("add", [TypeInfo.get(keyName), TypeInfo.get(valName)])
        let jobj = value.asObject()
        for ((k, jv) in jobj.getFields()) {
            let keyVal = readValue(JsonString(k), TypeInfo.get(keyName), options, depth + 1)
            let valVal = readValue(jv, TypeInfo.get(valName), options, depth + 1)
            addFunc.apply(map, [keyVal, valVal])
        }
        map
    }

    /// JsonValue → 通用 Any（动态结构）
    private static func jsonToAny(v: JsonValue): Any {
        match (v.kind()) {
            case JsNull => None
            case JsBool => v.asBool().getValue()
            case JsInt => v.asInt().getValue()
            case JsFloat => v.asFloat().getValue()
            case JsString => v.asString().getValue()
            case JsArray =>
                var list = ArrayList<Any>()
                for (item in v.asArray().getItems()) {
                    list.add(jsonToAny(item))
                }
                list.toArray()
            case JsObject =>
                var map = HashMap<String, Any>()
                for ((k, val) in v.asObject().getFields()) {
                    map[k] = jsonToAny(val)
                }
                map
        }
    }

    // ===== 宽松类型转换 =====

    private static func readString(v: JsonValue): String {
        if (let s: JsonString <- v) { return s.getValue() }
        if (let i: JsonInt <- v) { return "${i.getValue()}" }
        if (let f: JsonFloat <- v) { return "${f.getValue()}" }
        if (let b: JsonBool <- v) { return "${b.getValue()}" }
        throw Exception("JsonSerializer: 无法转换为 String")
    }

    private static func readInt64(v: JsonValue): Int64 {
        if (let i: JsonInt <- v) { return i.getValue() }
        if (let f: JsonFloat <- v) { return Int64(f.getValue()) }
        if (let s: JsonString <- v) { return Int64.parse(s.getValue()) }
        throw Exception("JsonSerializer: 无法转换为 Int64")
    }

    private static func readFloat64(v: JsonValue): Float64 {
        if (let f: JsonFloat <- v) { return f.getValue() }
        if (let i: JsonInt <- v) { return Float64(i.getValue()) }
        if (let s: JsonString <- v) { return Float64.parse(s.getValue()) }
        throw Exception("JsonSerializer: 无法转换为 Float64")
    }

    private static func readBool(v: JsonValue): Bool {
        if (let b: JsonBool <- v) { return b.getValue() }
        if (let s: JsonString <- v) { return s.getValue() == "true" }
        throw Exception("JsonSerializer: 无法转换为 Bool")
    }

    private static func readChar(v: JsonValue): Rune {
        let s = readString(v)
        for (r in s.runes()) {
            return r
        }
        throw Exception("JsonSerializer: 无法转换为 Char")
    }

    /// 生成某类型的占位默认值（用于构造 Option<X> 的 None：None 的参数槽类型是 X）。
    private static func defaultValueFor(typeName: String): Any {
        match (typeName) {
            case "String" => return ""
            case "Bool" => return false
            case "Int64" => return Int64(0)
            case "Int32" => return Int32(0)
            case "Int16" => return Int16(0)
            case "Int8" => return Int8(0)
            case "UInt64" => return UInt64(0)
            case "UInt32" => return UInt32(0)
            case "UInt16" => return UInt16(0)
            case "UInt8" => return UInt8(0)
            case "Float64" => return Float64(0.0)
            case "Float32" => return Float32(0.0)
            case "Rune" => return Rune(0)
            case _ => ()
        }
        // 集合/对象/枚举：反射无参构造；失败则抛异常
        if (let ct: ClassTypeInfo <- TypeInfo.get(typeName)) {
            return ct.construct([])
        }
        if (let et: EnumTypeInfo <- TypeInfo.get(typeName)) {
            // constructors 是 Collection：取第一个构造器名
            let first = et.constructors.iterator().next().getOrThrow()
            let ctor = et.getConstructor(first.name, argsCount: 0)
            return ctor.apply([])
        }
        throw Exception("JsonSerializer: 无法为 Option 占位值构造类型 ${typeName}")
    }
}