package peco

import (
	"bufio"
	"io"
	"sync"
	"time"

	"github.com/lestrrat/go-pdebug"
	"github.com/peco/peco/internal/util"
	"github.com/peco/peco/pipeline"
	"github.com/pkg/errors"
	"golang.org/x/net/context"
)

func NewFilteredBuffer(src Buffer, page, perPage int) *FilteredBuffer {
	fb := FilteredBuffer{
		src: src,
	}

	s := perPage * (page - 1)
	if s > src.Size() {
		return &fb
	}

	selection := make([]int, 0, src.Size())
	e := s + perPage
	if e >= src.Size() {
		e = src.Size()
	}

	for i := s; i < e; i++ {
		selection = append(selection, i)
	}
	fb.selection = selection

	return &fb
}

func (flb *FilteredBuffer) Append(l Line) (Line, error) {
	return l, nil
}

// LineAt returns the line at index `i`. Note that the i-th element
// in this filtered buffer may actually correspond to a totally
// different line number in the source buffer.
func (flb FilteredBuffer) LineAt(i int) (Line, error) {
	if i >= len(flb.selection) {
		return nil, errors.Errorf("specified index %d is out of range", len(flb.selection))
	}
	return flb.src.LineAt(flb.selection[i])
}

// Size returns the number of lines in the buffer
func (flb FilteredBuffer) Size() int {
	return len(flb.selection)
}

func NewMemoryBuffer() *MemoryBuffer {
	return &MemoryBuffer{
		done: make(chan struct{}),
	}
}

func (mb *MemoryBuffer) Size() int {
	mb.mutex.Lock()
	defer mb.mutex.Unlock()
	return len(mb.lines)
}

func (mb *MemoryBuffer) Reset() {
	mb.mutex.Lock()
	defer mb.mutex.Unlock()
	mb.done = make(chan struct{})
	mb.lines = []Line(nil)
}

func (mb *MemoryBuffer) Done() <-chan struct{} {
	mb.mutex.Lock()
	defer mb.mutex.Unlock()
	return mb.done
}

func (mb *MemoryBuffer) Accept(ctx context.Context, p pipeline.Producer) {
	mb.mutex.Lock()
	defer mb.mutex.Unlock()
	if pdebug.Enabled {
		g := pdebug.Marker("MemoryBuffer.Accept")
		defer g.End()
	}
	defer close(mb.done)

	for {
		select {
		case <-ctx.Done():
			if pdebug.Enabled {
				pdebug.Printf("MemoryBuffer received context done")
			}
			return
		case v := <-p.OutCh():
			switch v.(type) {
			case error:
				if pipeline.IsEndMark(v.(error)) {
					if pdebug.Enabled {
						pdebug.Printf("MemoryBuffer received end mark (read %d lines)", len(mb.lines))
					}
					return
				}
			case Line:
				mb.lines = append(mb.lines, v.(Line))
			}
		}
	}
}

func (mb *MemoryBuffer) LineAt(n int) (Line, error) {
	mb.mutex.Lock()
	defer mb.mutex.Unlock()

	if s := len(mb.lines); s <= 0 || n >= s {
		return nil, errors.New("empty buffer")
	}

	return mb.lines[n], nil
}

// Creates a new Source. Does not start processing the input until you
// call Setup()
func NewSource(in io.Reader, enableSep bool) *Source {
	return &Source{
		in:            in, // Note that this may be closed, so do not rely on it
		enableSep:     enableSep,
		done:          make(chan struct{}),
		ready:         make(chan struct{}),
		setupOnce:     sync.Once{},
		OutputChannel: pipeline.OutputChannel(make(chan interface{})),
	}
}

// Setup reads from the input os.File.
func (s *Source) Setup(state *Peco) {
	s.setupOnce.Do(func() {
		s.mutex.Lock()
		defer s.mutex.Unlock()

		done := make(chan struct{})
		refresh := make(chan struct{}, 1)
		defer close(done)
		defer close(refresh)

		draw := func(state *Peco) {
			// Not a great thing to do, allowing nil to be passed
			// as state, but for testing I couldn't come up with anything
			// better for the moment
			if state != nil && !state.ExecQuery() {
				state.Hub().SendDraw(false)
			}
		}

		go func() {
			ticker := time.NewTicker(100 * time.Millisecond)
			defer ticker.Stop()

			for {
				select {
				case <-done:
					draw(state)
					return
				case <-ticker.C:
					draw(state)
				}
			}
		}()

		// This sync.Once var is used to receive the notification
		// that there was at least 1 line read from the source
		var notify sync.Once
		notifycb := func() {
			// close the ready channel so others can be notified
			// that there's at least 1 line in the buffer
			close(s.ready)
		}
		scanner := bufio.NewScanner(s.in)
		defer func() {
			if util.IsTty(s.in) {
				return
			}
			if closer, ok := s.in.(io.Closer); ok {
				closer.Close()
			}
		}()

		readCount := 0
		for scanner.Scan() {
			txt := scanner.Text()
			readCount++
			s.lines = append(s.lines, NewRawLine(txt, s.enableSep))
			notify.Do(notifycb)
		}

		// XXX Just in case scanner.Scan() did not return a single line...
		// Note: this will be a no-op if notify.Do has been called before
		notify.Do(notifycb)
		// And also, close the done channel so we can tell the consumers
		// we have finished reading everything
		close(s.done)

		if pdebug.Enabled {
			pdebug.Printf("Read all %d lines from source", readCount)
		}
	})
}

// Start starts
func (s *Source) Start(ctx context.Context) {
	if pdebug.Enabled {
		g := pdebug.Marker("Source.Start")
		defer g.End()
		defer pdebug.Printf("Source sent %d lines", len(s.lines))
	}
	defer s.OutputChannel.SendEndMark("end of input")
	defer close(s.done)

	for _, l := range s.lines {
		select {
		case <-ctx.Done():
			if pdebug.Enabled {
				pdebug.Printf("Source: context.Done detected")
			}
			return
		case s.OutputChannel <- l:
			// no op
		}
	}
}

// Reset resets the state of the source object so that it
// is ready to feed the filters
func (s *Source) Reset() {
	s.done = make(chan struct{})
	s.OutputChannel = pipeline.OutputChannel(make(chan interface{}))
}

// Ready returns the "input ready" channel. It will be closed as soon as
// the first line of input is processed via Setup()
func (s *Source) Ready() <-chan struct{} {
	return s.ready
}

// Done returns the "read all lines" channel. It will be closed as soon as
// the all input has been read
func (s *Source) Done() <-chan struct{} {
	return s.done
}