package build

import (
	"git.akyoto.dev/cli/q/src/build/arch/x64"
	"git.akyoto.dev/cli/q/src/build/asm"
	"git.akyoto.dev/cli/q/src/build/os/linux"
)

// Result contains all the compiled functions in a build.
type Result struct {
	Functions        map[string]*Function
	instructionCount int
}

// Finalize generates the final machine code.
func (r Result) Finalize() ([]byte, []byte) {
	// This will be the entry point of the executable.
	// The only job of the entry function is to call `main` and exit cleanly.
	// The reason we call `main` instead of using `main` itself is to place
	// a return address on the stack, which allows return statements in `main`.
	final := asm.Assembler{
		Instructions: make([]asm.Instruction, 0, r.instructionCount+4),
	}

	final.Call("main")
	final.RegisterNumber(asm.MOVE, x64.SyscallRegisters[0], linux.Exit)
	final.RegisterNumber(asm.MOVE, x64.SyscallRegisters[1], 0)
	final.Syscall()

	// Place the `main` function immediately after the entry point.
	main := r.Functions["main"]
	delete(r.Functions, "main")
	final.Merge(&main.Assembler)

	// Merge all the remaining functions.
	for _, f := range r.Functions {
		final.Merge(&f.Assembler)
	}

	code, data := final.Finalize()
	return code, data
}