package dwarf

import (
	"bytes"
	"encoding/binary"

	log "github.com/sirupsen/logrus"

	. "ios-wrapper/pkg/leb128"
)

type header struct {
	unit_length                        uint32
	version                            uint16
	header_length                      uint32
	minimum_instruction_length         uint8
	maximum_operations_per_instruction uint8
	default_is_stmt                    uint8
	line_base                          int8
	line_range                         uint8
	opcode_base                        uint8
}

type register struct {
	address        uint64
	op_index       uint32
	file           uint32
	line           uint32
	column         uint32
	is_stmt        bool
	basic_block    bool
	end_sequence   bool
	prologue_end   bool
	epilogue_begin bool
	isa            uint32
	discriminator  uint32
}

func initRegister(is_stmt bool) register {
	var reg register
	reg.is_stmt = is_stmt
	reg.file = 1
	reg.line = 1
	return reg
}

func (reg *register) reset() {
	reg.basic_block = false
	reg.prologue_end = false
	reg.epilogue_begin = false
	reg.discriminator = 0
}

// Opcodes
const (
	Copy             uint8 = 1
	AdvancePc        uint8 = 2
	AdvanceLine      uint8 = 3
	SetFile          uint8 = 4
	SetColumn        uint8 = 5
	NegateStmt       uint8 = 6
	SetBasicBlock    uint8 = 7
	ConstAddPc       uint8 = 8
	FixedAdvancePc   uint8 = 9
	SetPrologueEnd   uint8 = 10
	SetEpiloqueBegin uint8 = 11
	SetIsa           uint8 = 12

	// Extended opcodes
	EndSequence      uint8 = 1
	SetAddress       uint8 = 2
	DefineFile       uint8 = 3
	SetDiscriminator uint8 = 4
)

type row struct {
	address      uint64
	op_index     uint32
	directory    string
	file         string
	line         int32
	column       int32
	end_sequence bool
}

type filename struct {
	name string
	dir  uint
}

type DebuglineParser struct {
	buf       *bytes.Buffer
	byteorder binary.ByteOrder
	header    header

	standard_opcode_lengths []uint8
	include_directories     []string
	file_names              []filename

	row []row
}

func (parser *DebuglineParser) Find(address uint64) (bool, uint32, string, string) {
	for _, row := range parser.row {
		if address == row.address {
			return true, uint32(row.line), row.directory, row.file
		}
	}
	return false, 0, "", ""
}

func (parser *DebuglineParser) Parse(buf *bytes.Buffer, byteorder binary.ByteOrder) {
	parser.buf = buf
	parser.byteorder = byteorder
	parser.parseHeader()
	parser.parseOpcode()
	parser.parseDirectoryTable()
	parser.parseFilenameTable()
	parser.parseStatementProgram()
}

func (parser *DebuglineParser) parseHeader() {
	binary.Read(parser.buf, parser.byteorder, &parser.header.unit_length)
	binary.Read(parser.buf, parser.byteorder, &parser.header.version)
	binary.Read(parser.buf, parser.byteorder, &parser.header.header_length)
	binary.Read(parser.buf, parser.byteorder, &parser.header.minimum_instruction_length)

	if parser.header.version >= 4 {
		binary.Read(parser.buf, parser.byteorder, &parser.header.maximum_operations_per_instruction)
	}

	binary.Read(parser.buf, parser.byteorder, &parser.header.default_is_stmt)
	binary.Read(parser.buf, parser.byteorder, &parser.header.line_base)
	binary.Read(parser.buf, parser.byteorder, &parser.header.line_range)
	binary.Read(parser.buf, parser.byteorder, &parser.header.opcode_base)
}

func (parser *DebuglineParser) parseOpcode() {
	var standard_opcode_lengths []uint8
	for i := uint8(1); i < parser.header.opcode_base; i++ {
		var num uint8
		binary.Read(parser.buf, parser.byteorder, &num)
		standard_opcode_lengths = append(standard_opcode_lengths, num)
	}
	parser.standard_opcode_lengths = standard_opcode_lengths
}

func (parser *DebuglineParser) parseDirectoryTable() {
	var include_directories []string
	for {
		dir, _ := parser.buf.ReadString(0)
		if dir == "\x00" {
			break
		}
		include_directories = append(include_directories, dir)
	}
	parser.include_directories = include_directories
}

func (parser *DebuglineParser) parseFilenameTable() {
	var file_names []filename
	for {
		file, _ := parser.buf.ReadString(0)
		if file == "\x00" {
			break
		}
		dir, _ := ReadULEB(parser.buf) // directory index
		ReadULEB(parser.buf)           // time
		ReadULEB(parser.buf)           // length
		file_names = append(file_names, filename{
			name: file,
			dir:  dir,
		})
	}
	parser.file_names = file_names
}

func (parser *DebuglineParser) parseStatementProgram() {
	reg := initRegister(parser.header.default_is_stmt == 1)

runloop:
	for {
		var opcode uint8
		binary.Read(parser.buf, parser.byteorder, &opcode)
		if opcode >= parser.header.opcode_base {
			adjusted_opcode := opcode - parser.header.opcode_base
			operation_advance := adjusted_opcode / parser.header.line_range
			increment_address_and_op_index(&reg, &parser.header, uint(operation_advance))
			reg.line += uint32(int32(parser.header.line_base) + int32(adjusted_opcode%parser.header.line_range))
			parser.register_to_matrix(&reg)
			reg.reset()
		} else if opcode == 0 {
			size_, _ := ReadULEB(parser.buf)
			size := size_ - 1
			var extended_opcode uint8
			binary.Read(parser.buf, parser.byteorder, &extended_opcode)
			switch extended_opcode {
			case EndSequence:
				reg.end_sequence = true
				parser.register_to_matrix(&reg)
				reg = initRegister(parser.header.default_is_stmt == 1)
				break runloop
			case SetAddress:
				if size == 8 {
					binary.Read(parser.buf, parser.byteorder, &reg.address)
				} else if size == 4 {
					var v uint32
					binary.Read(parser.buf, parser.byteorder, &v)
					reg.address = uint64(v)
				} else {
					parser.buf.Next(int(size))
				}
				reg.op_index = 0
			case SetDiscriminator:
				v, _ := ReadULEB(parser.buf)
				reg.discriminator = uint32(v)
			default:
				parser.buf.Next(int(size))
			}
		} else {
			switch opcode {
			case Copy:
				parser.register_to_matrix(&reg)
				reg.reset()
			case AdvancePc:
				v, _ := ReadULEB(parser.buf)
				increment_address_and_op_index(&reg, &parser.header, v)
			case AdvanceLine:
				v, _ := ReadSLEB(parser.buf)
				if v < 0 {
					reg.line -= uint32(-v)
				} else {
					reg.line += uint32(v)
				}
			case SetFile:
				v, _ := ReadULEB(parser.buf)
				reg.file = uint32(v)
			case SetColumn:
				v, _ := ReadULEB(parser.buf)
				reg.column = uint32(v)
			case NegateStmt:
				reg.is_stmt = !reg.is_stmt
			case SetBasicBlock:
				reg.basic_block = true
			case ConstAddPc:
				adjusted_opcode := 255 - parser.header.opcode_base
				operation_advance := adjusted_opcode / parser.header.line_range
				increment_address_and_op_index(&reg, &parser.header, uint(operation_advance))
			case FixedAdvancePc:
				var v uint16
				binary.Read(parser.buf, parser.byteorder, &v)
				reg.address += uint64(v)
				reg.op_index = 0
			case SetPrologueEnd:
				reg.prologue_end = true
			case SetEpiloqueBegin:
				reg.epilogue_begin = true
			case SetIsa:
				v, _ := ReadULEB(parser.buf)
				reg.isa = uint32(v)
			default:
				break
			}
		}
	}
}

func increment_address_and_op_index(reg *register, h *header, operation_advance uint) {
	min_length := uint64(h.minimum_instruction_length)
	max_op := uint64(h.maximum_operations_per_instruction)
	advance := uint64(operation_advance)
	op_index := uint64(reg.op_index)

	if h.maximum_operations_per_instruction == 1 {
		reg.address += advance * min_length
	} else {
		reg.address += min_length * ((op_index + advance) / max_op)
		reg.op_index = uint32((op_index + advance) % max_op)
	}
}

func (parser *DebuglineParser) register_to_matrix(reg *register) {
	if !(reg.is_stmt || (reg.line > 0 && reg.column > 0)) {
		return
	}

	file := parser.file_names[reg.file-1]
	path := parser.include_directories[file.dir-1]
	row := row{
		address:      reg.address,
		op_index:     reg.op_index,
		directory:    path,
		file:         file.name,
		line:         int32(reg.line),
		column:       int32(reg.column),
		end_sequence: reg.end_sequence,
	}
	parser.row = append(parser.row, row)
	log.WithFields(log.Fields{
		"address":   row.address,
		"directory": row.directory,
		"file":      row.file,
		"line":      row.line,
	}).Trace("Debugline Row")
}