package evaluator

import (
	"fmt"
	"os"

	"code.jmug.me/jmug/compiler-in-go/pkg/object"
)

var builtins = map[string]*object.Builtin{
	"puts": {
		Fn: func(args ...object.Object) object.Object {
			for _, arg := range args {
				fmt.Println(arg.Inspect())
			}
			return _NULL
		},
	},
	"len": {
		Fn: func(args ...object.Object) object.Object {
			if len(args) != 1 {
				return newError("wrong number of arguments. got=%d, want=1",
					len(args))
			}

			switch arg := args[0].(type) {
			case *object.String:
				return &object.Integer{Value: int64(len(arg.Value))}
			case *object.Array:
				return &object.Integer{Value: int64(len(arg.Elements))}
			default:
				return newError("argument to `len` not supported, got %s",
					args[0].Type())
			}
		},
	},
	"first": {
		Fn: func(args ...object.Object) object.Object {
			if len(args) != 1 {
				return newError("wrong number of arguments. got=%d, want=1",
					len(args))
			}
			if args[0].Type() != object.ARRAY_OBJ {
				return newError("argument to `first` must be ARRAY, got %s",
					args[0].Type())
			}

			arr := args[0].(*object.Array)
			if len(arr.Elements) > 0 {
				return arr.Elements[0]
			}

			return _NULL
		},
	},
	"last": {
		Fn: func(args ...object.Object) object.Object {
			if len(args) != 1 {
				return newError("wrong number of arguments. got=%d, want=1",
					len(args))
			}
			if args[0].Type() != object.ARRAY_OBJ {
				return newError("argument to `last` must be ARRAY, got %s",
					args[0].Type())
			}

			arr := args[0].(*object.Array)
			if len(arr.Elements) > 0 {
				return arr.Elements[len(arr.Elements)-1]
			}
			return _NULL
		},
	},
	"rest": {
		Fn: func(args ...object.Object) object.Object {
			if len(args) != 1 {
				return newError("wrong number of arguments. got=%d, want=1",
					len(args))
			}
			if args[0].Type() != object.ARRAY_OBJ {
				return newError("argument to `rest` must be ARRAY, got %s",
					args[0].Type())
			}
			arr := args[0].(*object.Array).Elements
			arrLen := len(arr)
			if arrLen > 0 {
				newArr := make([]object.Object, arrLen-1)
				copy(newArr, arr[1:])
				return &object.Array{Elements: newArr}
			}
			return _NULL
		},
	},
	"push": {
		Fn: func(args ...object.Object) object.Object {
			if len(args) != 2 {
				return newError("wrong number of arguments. got=%d, want=2",
					len(args))
			}
			if args[0].Type() != object.ARRAY_OBJ {
				return newError("argument to `push` must be ARRAY, got %s",
					args[0].Type())
			}
			arr := args[0].(*object.Array).Elements
			arrLen := len(arr)
			newArr := make([]object.Object, arrLen+1)
			copy(newArr, arr)
			newArr[arrLen] = args[1]
			return &object.Array{Elements: newArr}
		},
	},
	"exit": {
		Fn: func(args ...object.Object) object.Object {
			if len(args) != 0 {
				return newError("exit takes no arguments...")
			}
			os.Exit(0)
			return nil // Make the compiler happy.
		},
	},
}