package sizer

import (
	"errors"
	"os"
	"path/filepath"
	"sync"
)

const (
	// FileType is a const representing a file
	FileType = iota
	// DirType is a const representing a directory
	DirType = iota
	// SymLinkType is a const representing a symbolic link
	SymLinkType = iota
	// HardLinkType is a const representing a hard link
	HardLinkType = iota
	// CharDevType is a const representing a char device
	CharDevType = iota
	// NamedPipeType is a const representing a named pipe
	NamedPipeType = iota
	// SocketType is a const representing a socket, both unix and network
	SocketType = iota
)

// INode is an entry in the filesystem. It can be:
//   - a file
//   - a directory
//   - a symbolic link
//   - a hard link
//   - a char device/named pipe/socket
// It takes a Kind (as above described), a Size and a Path
type INode struct {
	Kind     int
	Size     int64
	Path     string
	Children *INodeList
}

// INodeList is a simple *INode slice with a Mutex to allow safe
// concurrent write.
type INodeList struct {
	Elements []*INode
	safe     sync.Mutex
}

type statusReport struct {
	path string
	err  error
}

// Append appends safely an inode to the INodeList.
func (il *INodeList) Append(node *INode) {
	il.safe.Lock()
	il.Elements = append(il.Elements, node)
	il.safe.Unlock()
}

// INodeChan is a channel global to the sizer package that is used
// to funnel the retrieved sizes and infos on the inodes.
var INodeChan chan *INode

// ErrNotIdenfiedType is the error returned when the a classifier does not
// recognize the INode type.
var ErrNotIdenfiedType = errors.New("inode not identified")

// NewINode returns a new *INode with kind, size and path
func NewINode(kind int, size int64, path string) *INode {
	var children INodeList
	abspath, _ := filepath.Abs(path)
	var newINode = INode{
		Kind:     kind,
		Size:     size,
		Path:     abspath,
		Children: &children,
	}
	return &newINode
}

// Name returns the name of the file at the INode.
func (i *INode) Name() string {
	_, name := filepath.Split(i.Path)
	return name
}

// IdentifyType classifies a file-like object in one of the FileType.
func IdentifyType(path string) (int, int64, error) {
	f, err := os.Lstat(path)
	if err != nil {
		return -1, 0, err
	}
	switch mode := f.Mode(); {
	case mode.IsDir():
		return DirType, f.Size(), nil
	case mode.IsRegular():
		return FileType, f.Size(), nil
	}
	return -1, 0, ErrNotIdenfiedType
}

func ls(path string) ([]string, error) {
	var content []string
	f, err := os.Open(path)
	defer f.Close()
	if err != nil {
		return []string{}, err
	}
	files, err := f.Readdir(-1)
	if err != nil {
		return []string{}, err
	}
	for _, fi := range files {
		content = append(content, filepath.Join(path, fi.Name()))
	}
	return content, nil
}

func runThrough(i *INode, ch chan int64, report chan statusReport, content []string) {
	Console.Debugln("Entering:", i.Path)
	for _, filepath := range content {
		f, err := os.Lstat(filepath)
		if err != nil {
			report <- statusReport{path: i.Path, err: err}
		}
		switch mode := f.Mode(); {
		case mode.IsDir():
			Console.Debugln(filepath, "is a directory")
			dirINode := NewINode(FileTypes["dir"], f.Size(), filepath)
			i.Children.Append(dirINode)
			ch <- f.Size()
			go dirINode.walkDir(report)
		case mode.IsRegular():
			Console.Debugln(filepath, "is a regular file")
			fileINode := NewINode(FileTypes["file"], f.Size(), filepath)
			i.Children.Append(fileINode)
			ch <- f.Size()
		default:
			Console.Debugln(filepath, "is NOT a regular file")
			var otherINode *INode
			inodeType, err := IdentifyType(filepath)
			if err != nil {
				if err != ErrNotIdenfiedType {
					report <- statusReport{path: filepath, err: err}
					return // Is this necessary?
				}
				otherINode = NewINode(-1, 0, filepath)
			} else {
				otherINode = NewINode(inodeType, 0, filepath)
			}
			i.Children.Append(otherINode)
		}
	}
	report <- statusReport{path: i.Path, err: nil}
}

func (i *INode) walkDir(reportUp chan statusReport) {
	ch := make(chan int64, 1)
	report := make(chan statusReport, 1)
	content, err := ls(i.Path)
	if err != nil {
		Console.Fatal(err)
	}
	go runThrough(i, ch, report, content)
	for {
		select {
		case size := <-ch:
			i.Size += size
		case status := <-report:
			Console.Debugf("[%s] Report from: %s\n", i.Path, status.path)
			if status.err != nil {
				Console.Debugln("Sending error. Path:", status.path, "- Err:", status.err)
				reportUp <- status
			}
			if status.err == nil {
				Console.Debugf("[%s] Received -> %s - Closing channel...\n",
					i.Path, status.path)
				reportUp <- status
				close(reportUp)
				return
			}
		}
	}
}

// Sizer is the main entrypoint for the computation of the size of a directory.
func (i *INode) Sizer() {
	if i.Kind == FileTypes["file"] {
		Console.Println("This is not a directory!")
		return
	}
	report := make(chan statusReport)
	go i.walkDir(report)
	for r := range report {
		if r.err != nil {
			Console.Fatalf("%s: %s", r.path, r.err)
		}
		Console.Printf("%s: %d", i.Path, i.Size)
	}
}