package luaplugin

import (
	"encoding/json"

	lua "github.com/yuin/gopher-lua"
)

// registerJSONAPI adds cliamp.json.{encode,decode} to the cliamp table.
func registerJSONAPI(L *lua.LState, cliamp *lua.LTable) {
	tbl := L.NewTable()

	// cliamp.json.decode(str) -> table
	L.SetField(tbl, "decode", L.NewFunction(func(L *lua.LState) int {
		str := L.CheckString(1)
		var v any
		if err := json.Unmarshal([]byte(str), &v); err != nil {
			L.Push(lua.LNil)
			L.Push(lua.LString(err.Error()))
			return 2
		}
		L.Push(jsonToLua(L, v))
		return 1
	}))

	// cliamp.json.encode(table) -> string
	L.SetField(tbl, "encode", L.NewFunction(func(L *lua.LState) int {
		val := L.Get(1)
		goVal := luaToGo(val)
		data, err := json.Marshal(goVal)
		if err != nil {
			L.Push(lua.LNil)
			L.Push(lua.LString(err.Error()))
			return 2
		}
		L.Push(lua.LString(string(data)))
		return 1
	}))

	L.SetField(cliamp, "json", tbl)
}

func jsonToLua(L *lua.LState, v any) lua.LValue {
	switch val := v.(type) {
	case nil:
		return lua.LNil
	case bool:
		return lua.LBool(val)
	case float64:
		return lua.LNumber(val)
	case string:
		return lua.LString(val)
	case []any:
		tbl := L.NewTable()
		for i, item := range val {
			tbl.RawSetInt(i+1, jsonToLua(L, item))
		}
		return tbl
	case map[string]any:
		tbl := L.NewTable()
		for k, item := range val {
			tbl.RawSetString(k, jsonToLua(L, item))
		}
		return tbl
	default:
		return lua.LNil
	}
}

func luaToGo(val lua.LValue) any {
	switch v := val.(type) {
	case *lua.LNilType:
		return nil
	case lua.LBool:
		return bool(v)
	case lua.LNumber:
		return float64(v)
	case lua.LString:
		return string(v)
	case *lua.LTable:
		// Detect if it's an array (sequential integer keys starting at 1).
		maxN := v.MaxN()
		if maxN > 0 {
			arr := make([]any, 0, maxN)
			for i := 1; i <= maxN; i++ {
				arr = append(arr, luaToGo(v.RawGetInt(i)))
			}
			return arr
		}
		m := make(map[string]any)
		v.ForEach(func(key, value lua.LValue) {
			if ks, ok := key.(lua.LString); ok {
				m[string(ks)] = luaToGo(value)
			}
		})
		return m
	default:
		return nil
	}
}