package core

import (
	"fmt"

	"git.akyoto.dev/cli/q/src/build/arch/x64"
	"git.akyoto.dev/cli/q/src/build/asm"
	"git.akyoto.dev/cli/q/src/build/ast"
	"git.akyoto.dev/cli/q/src/build/cpu"
	"git.akyoto.dev/cli/q/src/build/errors"
	"git.akyoto.dev/cli/q/src/build/fs"
	"git.akyoto.dev/cli/q/src/build/token"
)

// Function represents the smallest unit of code.
type Function struct {
	Name string
	File *fs.File
	Body token.List
	state
}

// NewFunction creates a new function.
func NewFunction(name string, file *fs.File, body token.List) *Function {
	return &Function{
		Name: name,
		File: file,
		Body: body,
		state: state{
			assembler: asm.Assembler{
				Instructions: make([]asm.Instruction, 0, 32),
			},
			cpu: cpu.CPU{
				Input:   x64.CallRegisters,
				General: x64.GeneralRegisters,
				Syscall: x64.SyscallRegisters,
				Output:  x64.ReturnValueRegisters,
			},
			variables: map[string]*Variable{},
			finished:  make(chan struct{}),
		},
	}
}

// Compile turns a function into machine code.
func (f *Function) Compile() {
	defer close(f.finished)
	f.assembler.Label(f.Name)
	f.err = f.CompileTokens(f.Body)
	f.assembler.Return()
}

// CompileTokens compiles a token list.
func (f *Function) CompileTokens(tokens token.List) error {
	tree, err := ast.Parse(tokens)

	if err != nil {
		err.(*errors.Error).File = f.File
		return err
	}

	return f.CompileAST(tree)
}

// CompileAST compiles an abstract syntax tree.
func (f *Function) CompileAST(tree ast.AST) error {
	for _, node := range tree {
		err := f.CompileASTNode(node)

		if err != nil {
			return err
		}
	}

	return nil
}

// CompileASTNode compiles a node in the AST.
func (f *Function) CompileASTNode(node ast.Node) error {
	switch node := node.(type) {
	case *ast.Assign:
		return f.CompileAssign(node)

	case *ast.Call:
		return f.CompileCall(node.Expression)

	case *ast.Define:
		return f.CompileDefinition(node)

	case *ast.Return:
		return f.CompileReturn(node)

	case *ast.Loop:
		return f.CompileLoop(node)

	default:
		panic("Unknown AST type")
	}
}

// Logf formats a message for verbose output.
func (f *Function) Logf(format string, data ...any) {
	fmt.Printf("[%s @ %d] %s\n", f, len(f.assembler.Instructions), fmt.Sprintf(format, data...))
}

// String returns the function name.
func (f *Function) String() string {
	return f.Name
}

// Wait will block until the compilation finishes.
func (f *Function) Wait() {
	<-f.finished
}