package service

import (
	"fmt"
	"go/parser"
	"go/token"
	"io"
	"sync"
)

// Service specifies the api logic of transforming a source code format into another target format.
type Service interface {
	Start() error
	SetHeaderWriter(io.Writer) error
	AddIncludeArduinoH(bool)
}

const (
	// ErrorWorkerReaderIsNil ...
	ErrorWorkerReaderIsNil = "Reader should not be nil"
	// ErrorWorkerWriterIsNil ...
	ErrorWorkerWriterIsNil = "Writer should not be nil"

	FunctionGoHelperPrefix = "__GoHelper_"
)

var (
	funcDeclarations       []string
	helpersForDeclarations []string
	dlock                  sync.Mutex
)

// defaultService specifies the api logic of transforming a source code format into another target format.
type defaultService struct {
	in                 io.Reader
	out                io.Writer
	header             io.Writer
	addIncludeArduinoH bool
}

// NewService creates a a new transpile and returns its address.
func NewService(in io.Reader, out io.Writer) Service {
	return &defaultService{
		in:  in,
		out: out,
	}
}

func (s *defaultService) SetHeaderWriter(w io.Writer) error {
	if w == nil {
		return fmt.Errorf("Empty")
	}

	s.header = w
	return nil
}

func (s *defaultService) AddIncludeArduinoH(add bool) {
	s.addIncludeArduinoH = add
}

// Start ...
func (s *defaultService) Start() error {
	if s.in == nil {
		return fmt.Errorf("Error: %s", ErrorWorkerReaderIsNil)
	}
	if s.out == nil {
		return fmt.Errorf("Error: %s", ErrorWorkerWriterIsNil)
	}
	// Read tokens from file by using Go's parser.
	fset := token.NewFileSet()
	file, err := parser.ParseFile(fset, "source.go", s.in, 0)
	if err != nil {
		return fmt.Errorf("ParseFile failed! %v", err)
	}
	// If source has no declarations then main it to an empty for loop.
	if file.Decls == nil {
		fmt.Fprint(s.out, "void loop() {}void setup() {}")
		return nil
	}
	// Use Goroutines to work concurrently.
	count := len(file.Decls)
	done := make(chan bool, count)
	dst := make([]chan string, count)
	for i := 0; i < count; i++ {
		dst[i] = make(chan string, 1)
	}

	constDeclarations = nil
	typeDeclarations = nil
	abstractClassDeclarations = nil
	classDeclarations = nil
	funcDeclarations = nil
	helpersForDeclarations = nil

	// Start a transpile with an individual channel for each declaration in the source file.
	go func() {
		for i, decl := range file.Decls {
			handleDecl(i, decl, dst[i], done)
		}
	}()
	// Wait for all workers are done.
	for i := 0; i < count; i++ {
		select {
		case <-done:
		}
	}

	s.printIncludeHeaders()
	s.printConstDeclarations()
	s.printTypeDeclarations()
	s.printAbstractClassDeclarations()
	s.printClassDeclarations()
	s.printFunctionDeclarations()
	s.printGoHelperDeclarations()

	// Print the ordered result.
	for i := 0; i < count; i++ {
		for content := range dst[i] {
			s.out.Write([]byte(content))
		}
	}

	s.out.Write([]byte("\n"))

	// Print the AST.
	// ast.Fprint(os.Stderr, fset, file, nil)
	return nil
}

func (s *defaultService) printIncludeHeaders() {
	if !s.addIncludeArduinoH {
		return
	}

	h := "#include <Arduino.h>\n\n"
	s.out.Write([]byte(h))
}
func (s *defaultService) printConstDeclarations() {
	dlock.Lock()
	defer dlock.Unlock()

	for _, c := range constDeclarations {
		d := c.String()
		s.out.Write([]byte(d + "\n"))
		if s.header != nil {
			s.header.Write([]byte(d + "\n"))
		}
	}
	s.out.Write([]byte("\n"))
}
func (s *defaultService) printTypeDeclarations() {
	dlock.Lock()
	defer dlock.Unlock()

	for _, c := range typeDeclarations {
		d := c.String()
		s.out.Write([]byte(d + "\n"))
		if s.header != nil {
			s.header.Write([]byte(d + "\n"))
		}
	}
	s.out.Write([]byte("\n"))
}
func (s *defaultService) printAbstractClassDeclarations() {
	dlock.Lock()
	defer dlock.Unlock()

	for _, c := range abstractClassDeclarations {
		d := c.String()
		s.out.Write([]byte(d + "\n"))
		if s.header != nil {
			s.header.Write([]byte(d + "\n"))
		}
	}
	s.out.Write([]byte("\n"))
}
func (s *defaultService) printClassDeclarations() {
	dlock.Lock()
	defer dlock.Unlock()

	for _, c := range classDeclarations {
		d := c.String()
		s.out.Write([]byte(d + "\n"))
		if s.header != nil {
			s.header.Write([]byte(d + "\n"))
		}
	}
	s.out.Write([]byte("\n"))
}
func (s *defaultService) printFunctionDeclarations() {
	dlock.Lock()
	defer dlock.Unlock()

	for _, f := range funcDeclarations {
		s.out.Write([]byte(f + "\n"))
		if s.header != nil {
			s.header.Write([]byte(f + "\n"))
		}
	}
	s.out.Write([]byte("\n"))
}
func (s *defaultService) printGoHelperDeclarations() {
	dlock.Lock()
	defer dlock.Unlock()

	for _, f := range helpersForDeclarations {
		helper := fmt.Sprintf(`void %v%v(void*) { %v(); vTaskDelete(NULL); }`,
			FunctionGoHelperPrefix, f, f)
		s.out.Write([]byte(helper + "\n"))
	}
	s.out.Write([]byte("\n"))
}