package main

import (
	"context"
	"sync"

	"github.com/docker-archive/go-p9p"
)

// Session implements the p9p.Session interface.
type Session struct {
	mu   sync.Mutex
	fids map[p9p.Fid]Fid
	*Root
}

type Fid struct {
	File
	uname string
}

type File interface {
	Qid() p9p.Qid
	Stat() (p9p.Dir, error)
	Open(mode p9p.Flag) error
	Remove() error
	Read(ctx context.Context, p []byte, offset int64) (n int, err error)
	Write(ctx context.Context, p []byte, offset int64) (n int, err error)
}

type Dir interface {
	File
	Create(ctx context.Context, name string, perm uint32, mode p9p.Flag) (File, error)
	Walk(ctx context.Context, name string) (File, error)
}

func NewSession(root *Root) p9p.Session {
	return &Session{
		fids: make(map[p9p.Fid]Fid),
		Root: root,
	}
}

func (s *Session) Auth(ctx context.Context, afid p9p.Fid, uname, aname string) (p9p.Qid, error) {
	return p9p.Qid{}, p9p.MessageRerror{"authfs: no authentication required"}
}

func (s *Session) Attach(ctx context.Context, fid, afid p9p.Fid, uname, aname string) (p9p.Qid, error) {
	s.mu.Lock()
	defer s.mu.Unlock()

	if _, exists := s.fids[fid]; exists {
		return p9p.Qid{}, p9p.ErrDupfid
	}
	f := Fid{s.root, uname}
	s.fids[fid] = f
	return f.Qid(), nil
}

func (s *Session) Clunk(ctx context.Context, fid p9p.Fid) error {
	s.mu.Lock()
	defer s.mu.Unlock()

	if _, ok := s.fids[fid]; ok {
		delete(s.fids, fid)
		return nil
	} else {
		return p9p.ErrUnknownfid
	}
}

func (s *Session) Remove(ctx context.Context, fid p9p.Fid) error {
	s.mu.Lock()
	defer s.mu.Unlock()

	f, ok := s.fids[fid]
	if !ok {
		return p9p.ErrUnknownfid
	}
	delete(s.fids, fid) // clunk
	return f.Remove()
}

func (s *Session) Walk(ctx context.Context, fid, newfid p9p.Fid, names ...string) ([]p9p.Qid, error) {
	s.mu.Lock()
	defer s.mu.Unlock()

	f, ok := s.fids[fid]
	if !ok {
		return nil, p9p.ErrUnknownfid
	}

	if _, exists := s.fids[newfid]; exists {
		return nil, p9p.ErrDupfid
	}

	var (
		qids []p9p.Qid
		err  error
		dot  = f
	)
	defer func() { s.fids[newfid] = dot }()
	for _, name := range names {
		dir, ok := dot.File.(Dir)
		if !ok {
			return qids, p9p.ErrWalknodir
		}
		dot.File, err = dir.Walk(ctx, name)
		if err != nil {
			return qids, err
		}
		qids = append(qids, dot.File.Qid())
	}
	return qids, nil
}

func (s *Session) Read(ctx context.Context, fid p9p.Fid, p []byte, offset int64) (n int, err error) {
	s.mu.Lock()
	defer s.mu.Unlock()

	if f, ok := s.fids[fid]; ok {
		return f.File.Read(ctx, p, offset)
	} else {
		return 0, p9p.ErrUnknownfid
	}
}

func (s *Session) Write(ctx context.Context, fid p9p.Fid, p []byte, offset int64) (n int, err error) {
	s.mu.Lock()
	defer s.mu.Unlock()

	if f, ok := s.fids[fid]; ok {
		return f.File.Write(ctx, p, offset)
	} else {
		return 0, p9p.ErrUnknownfid
	}
}

func (s *Session) Open(ctx context.Context, fid p9p.Fid, mode p9p.Flag) (p9p.Qid, uint32, error) {
	s.mu.Lock()
	defer s.mu.Unlock()

	f, ok := s.fids[fid]
	if !ok {
		return p9p.Qid{}, 0, p9p.ErrUnknownfid
	}
	if err := f.Open(mode); err != nil {
		return p9p.Qid{}, 0, err
	}
	return f.File.Qid(), 0, nil
}

func (s *Session) Create(ctx context.Context, parent p9p.Fid, name string, perm uint32, mode p9p.Flag) (p9p.Qid, uint32, error) {
	s.mu.Lock()
	defer s.mu.Unlock()

	f, ok := s.fids[parent]
	if !ok {
		return p9p.Qid{}, 0, p9p.ErrUnknownfid
	}
	dir, ok := f.File.(Dir)
	if !ok {
		return p9p.Qid{}, 0, p9p.ErrCreatenondir
	}

	child, err := dir.Create(ctx, name, perm, mode)
	return child.Qid(), 0, err
}

func (s *Session) Stat(ctx context.Context, fid p9p.Fid) (p9p.Dir, error) {
	s.mu.Lock()
	defer s.mu.Unlock()

	if f, ok := s.fids[fid]; ok {
		return f.File.Stat()
	} else {
		return p9p.Dir{}, p9p.ErrUnknownfid
	}
}

func (s *Session) WStat(ctx context.Context, fid p9p.Fid, dir p9p.Dir) error {
	return p9p.ErrPerm
}

func (s *Session) Version() (msize int, version string) {
	return p9p.DefaultMSize, p9p.DefaultVersion
}