package asmc

import (
	"encoding/binary"
	"fmt"
	"slices"

	"git.urbach.dev/cli/q/src/config"
	"git.urbach.dev/cli/q/src/fs"
	"git.urbach.dev/cli/q/src/sizeof"
)

// resolvePointers resolves the addresses of all pointers within the code and writes the correct addresses to the code slice.
func (c *compiler) resolvePointers() {
restart:
	for i, pointer := range c.codePointers {
		address := pointer.Resolve()

		if sizeof.Signed(int32(address)) > int(pointer.Size) {
			left := c.code[:pointer.Position-Address(pointer.OpSize)]
			right := c.code[pointer.Position+Address(pointer.Size):]
			size := pointer.Size + pointer.OpSize
			opCode := c.code[pointer.Position-Address(pointer.OpSize)]

			var jump []byte

			switch opCode {
			case 0x74: // JE
				jump = []byte{0x0F, 0x84}
			case 0x75: // JNE
				jump = []byte{0x0F, 0x85}
			case 0x7C: // JL
				jump = []byte{0x0F, 0x8C}
			case 0x7D: // JGE
				jump = []byte{0x0F, 0x8D}
			case 0x7E: // JLE
				jump = []byte{0x0F, 0x8E}
			case 0x7F: // JG
				jump = []byte{0x0F, 0x8F}
			case 0xEB: // JMP
				jump = []byte{0xE9}
			default:
				panic(fmt.Sprintf("failed to increase pointer size for instruction 0x%x", opCode))
			}

			pointer.Position += Address(len(jump) - int(pointer.OpSize))
			pointer.OpSize = uint8(len(jump))
			pointer.Size = 4
			jump = binary.LittleEndian.AppendUint32(jump, uint32(address))
			offset := Address(len(jump)) - Address(size)

			for _, following := range c.codePointers[i+1:] {
				following.Position += offset
			}

			for key, address := range c.codeLabels {
				if address > pointer.Position {
					c.codeLabels[key] += offset
				}
			}

			c.code = slices.Concat(left, jump, right)
			goto restart
		}

		slice := c.code[pointer.Position : pointer.Position+Address(pointer.Size)]

		switch pointer.Size {
		case 1:
			slice[0] = uint8(address)
		case 2:
			binary.LittleEndian.PutUint16(slice, uint16(address))
		case 4:
			binary.LittleEndian.PutUint32(slice, uint32(address))
		case 8:
			binary.LittleEndian.PutUint64(slice, uint64(address))
		}
	}

	dataStart, _ := fs.Align(c.codeStart+Address(len(c.code)), config.Align)

	for _, pointer := range c.dataPointers {
		address := config.BaseAddress + dataStart + pointer.Resolve() + 8
		slice := c.code[pointer.Position : pointer.Position+4]
		binary.LittleEndian.PutUint32(slice, uint32(address))
	}

	if config.TargetOS == config.Windows {
		importsStart, _ := fs.Align(dataStart+Address(len(c.data)), config.Align)

		for _, pointer := range c.dllPointers {
			destination := importsStart + pointer.Resolve()
			from := c.codeStart + pointer.Position + Address(pointer.Size)
			offset := destination - from
			slice := c.code[pointer.Position : pointer.Position+4]
			binary.LittleEndian.PutUint32(slice, uint32(offset))
		}
	}
}