package json

import (
	"fmt"
	"reflect"
	"strings"
	"unsafe"
)

type opType int

const (
	opEnd opType = iota
	opInt
	opInt8
	opInt16
	opInt32
	opInt64
	opUint
	opUint8
	opUint16
	opUint32
	opUint64
	opFloat32
	opFloat64
	opString
	opBool
	opPtr
	opSliceHead
	opSliceElem
	opSliceEnd
	opStructFieldHead
	opStructFieldHeadInt
	opStructFieldHeadInt8
	opStructFieldHeadInt16
	opStructFieldHeadInt32
	opStructFieldHeadInt64
	opStructFieldHeadUint
	opStructFieldHeadUint8
	opStructFieldHeadUint16
	opStructFieldHeadUint32
	opStructFieldHeadUint64
	opStructFieldHeadFloat32
	opStructFieldHeadFloat64
	opStructFieldHeadString
	opStructFieldHeadBool
	opStructFieldPtrHead
	opStructFieldPtrHeadInt
	opStructFieldPtrHeadInt8
	opStructFieldPtrHeadInt16
	opStructFieldPtrHeadInt32
	opStructFieldPtrHeadInt64
	opStructFieldPtrHeadUint
	opStructFieldPtrHeadUint8
	opStructFieldPtrHeadUint16
	opStructFieldPtrHeadUint32
	opStructFieldPtrHeadUint64
	opStructFieldPtrHeadFloat32
	opStructFieldPtrHeadFloat64
	opStructFieldPtrHeadString
	opStructFieldPtrHeadBool
	opStructField
	opStructFieldInt
	opStructFieldInt8
	opStructFieldInt16
	opStructFieldInt32
	opStructFieldInt64
	opStructFieldUint
	opStructFieldUint8
	opStructFieldUint16
	opStructFieldUint32
	opStructFieldUint64
	opStructFieldFloat32
	opStructFieldFloat64
	opStructFieldString
	opStructFieldBool
	opStructEnd
)

func (t opType) String() string {
	switch t {
	case opEnd:
		return "END"
	case opInt:
		return "INT"
	case opInt8:
		return "INT8"
	case opInt16:
		return "INT16"
	case opInt32:
		return "INT32"
	case opInt64:
		return "INT64"
	case opUint:
		return "UINT"
	case opUint8:
		return "UINT8"
	case opUint16:
		return "UINT16"
	case opUint32:
		return "UINT32"
	case opUint64:
		return "UINT64"
	case opFloat32:
		return "FLOAT32"
	case opFloat64:
		return "FLOAT64"
	case opString:
		return "STRING"
	case opBool:
		return "BOOL"
	case opPtr:
		return "PTR"
	case opSliceHead:
		return "SLICE_HEAD"
	case opSliceElem:
		return "SLICE_ELEM"
	case opSliceEnd:
		return "SLICE_END"
	case opStructFieldHead:
		return "STRUCT_FIELD_HEAD"
	case opStructFieldHeadInt:
		return "STRUCT_FIELD_HEAD_INT"
	case opStructFieldHeadInt8:
		return "STRUCT_FIELD_HEAD_INT8"
	case opStructFieldHeadInt16:
		return "STRUCT_FIELD_HEAD_INT16"
	case opStructFieldHeadInt32:
		return "STRUCT_FIELD_HEAD_INT32"
	case opStructFieldHeadInt64:
		return "STRUCT_FIELD_HEAD_INT64"
	case opStructFieldHeadUint:
		return "STRUCT_FIELD_HEAD_UINT"
	case opStructFieldHeadUint8:
		return "STRUCT_FIELD_HEAD_UINT8"
	case opStructFieldHeadUint16:
		return "STRUCT_FIELD_HEAD_UINT16"
	case opStructFieldHeadUint32:
		return "STRUCT_FIELD_HEAD_UINT32"
	case opStructFieldHeadUint64:
		return "STRUCT_FIELD_HEAD_UINT64"
	case opStructFieldHeadFloat32:
		return "STRUCT_FIELD_HEAD_FLOAT32"
	case opStructFieldHeadFloat64:
		return "STRUCT_FIELD_HEAD_FLOAT64"
	case opStructFieldHeadString:
		return "STRUCT_FIELD_HEAD_STRING"
	case opStructFieldHeadBool:
		return "STRUCT_FIELD_HEAD_BOOL"
	case opStructFieldPtrHead:
		return "STRUCT_FIELD_PTR_HEAD"
	case opStructFieldPtrHeadInt:
		return "STRUCT_FIELD_PTR_HEAD_INT"
	case opStructFieldPtrHeadInt8:
		return "STRUCT_FIELD_PTR_HEAD_INT8"
	case opStructFieldPtrHeadInt16:
		return "STRUCT_FIELD_PTR_HEAD_INT16"
	case opStructFieldPtrHeadInt32:
		return "STRUCT_FIELD_PTR_HEAD_INT32"
	case opStructFieldPtrHeadInt64:
		return "STRUCT_FIELD_PTR_HEAD_INT64"
	case opStructFieldPtrHeadUint:
		return "STRUCT_FIELD_PTR_HEAD_UINT"
	case opStructFieldPtrHeadUint8:
		return "STRUCT_FIELD_PTR_HEAD_UINT8"
	case opStructFieldPtrHeadUint16:
		return "STRUCT_FIELD_PTR_HEAD_UINT16"
	case opStructFieldPtrHeadUint32:
		return "STRUCT_FIELD_PTR_HEAD_UINT32"
	case opStructFieldPtrHeadUint64:
		return "STRUCT_FIELD_PTR_HEAD_UINT64"
	case opStructFieldPtrHeadFloat32:
		return "STRUCT_FIELD_PTR_HEAD_FLOAT32"
	case opStructFieldPtrHeadFloat64:
		return "STRUCT_FIELD_PTR_HEAD_FLOAT64"
	case opStructFieldPtrHeadString:
		return "STRUCT_FIELD_PTR_HEAD_STRING"
	case opStructFieldPtrHeadBool:
		return "STRUCT_FIELD_PTR_HEAD_BOOL"
	case opStructField:
		return "STRUCT_FIELD"
	case opStructFieldInt:
		return "STRUCT_FIELD_INT"
	case opStructFieldInt8:
		return "STRUCT_FIELD_INT8"
	case opStructFieldInt16:
		return "STRUCT_FIELD_INT16"
	case opStructFieldInt32:
		return "STRUCT_FIELD_INT32"
	case opStructFieldInt64:
		return "STRUCT_FIELD_INT64"
	case opStructFieldUint:
		return "STRUCT_FIELD_UINT"
	case opStructFieldUint8:
		return "STRUCT_FIELD_UINT8"
	case opStructFieldUint16:
		return "STRUCT_FIELD_UINT16"
	case opStructFieldUint32:
		return "STRUCT_FIELD_UINT32"
	case opStructFieldUint64:
		return "STRUCT_FIELD_UINT64"
	case opStructFieldFloat32:
		return "STRUCT_FIELD_FLOAT32"
	case opStructFieldFloat64:
		return "STRUCT_FIELD_FLOAT64"
	case opStructFieldString:
		return "STRUCT_FIELD_STRING"
	case opStructFieldBool:
		return "STRUCT_FIELD_BOOL"
	case opStructEnd:
		return "STRUCT_END"
	}
	return ""
}

type opcodeHeader struct {
	op   opType
	typ  *rtype
	ptr  uintptr
	next *opcode
}

type opcode struct {
	*opcodeHeader
}

func newOpCode(op opType, typ *rtype, next *opcode) *opcode {
	return &opcode{
		opcodeHeader: &opcodeHeader{
			op:   op,
			typ:  typ,
			next: next,
		},
	}
}

func newEndOp() *opcode {
	return newOpCode(opEnd, nil, nil)
}

func (c *opcode) beforeLastCode() *opcode {
	code := c
	for {
		var nextCode *opcode
		if code.op == opSliceElem {
			nextCode = code.toSliceElemCode().end
		} else {
			nextCode = code.next
		}
		if nextCode.op == opEnd {
			return code
		}
		code = nextCode
	}
	return nil
}

func (c *opcode) dump() string {
	codes := []string{}
	for code := c; code.op != opEnd; {
		codes = append(codes, fmt.Sprintf("%s", code.op))
		if code.op == opSliceElem {
			code = code.toSliceElemCode().end
		} else {
			code = code.next
		}
	}
	return strings.Join(codes, "\n")
}

func (c *opcode) toSliceHeaderCode() *sliceHeaderCode {
	return (*sliceHeaderCode)(unsafe.Pointer(c))
}

func (c *opcode) toSliceElemCode() *sliceElemCode {
	return (*sliceElemCode)(unsafe.Pointer(c))
}

func (c *opcode) toStructFieldCode() *structFieldCode {
	return (*structFieldCode)(unsafe.Pointer(c))
}

type sliceHeaderCode struct {
	*opcodeHeader
	elem *sliceElemCode
	end  *opcode
}

func newSliceHeaderCode() *sliceHeaderCode {
	return &sliceHeaderCode{
		opcodeHeader: &opcodeHeader{
			op: opSliceHead,
		},
	}
}

type sliceElemCode struct {
	*opcodeHeader
	idx  uintptr
	len  uintptr
	size uintptr
	data uintptr
	end  *opcode
}

func (c *sliceElemCode) set(header *reflect.SliceHeader) {
	c.idx = uintptr(0)
	c.len = uintptr(header.Len)
	c.data = header.Data
}

type structFieldCode struct {
	*opcodeHeader
	key       []byte
	offset    uintptr
	nextField *opcode
	end       *opcode
}