package main

import (
	"context"
	"errors"
	"sync"
)

type ByteFIFO struct {
	buffer []byte     // The underlying byte slice
	mutex  sync.Mutex // Mutex for thread safety
	cond   *sync.Cond // Condition variable for signaling
	cap    int        // Capacity of the buffer
}

// NewByteFIFO creates a new ByteFIFO with the given capacity.
func NewByteFIFO(capacity int) *ByteFIFO {
	fifo := &ByteFIFO{
		buffer: make([]byte, 0, capacity),
		cap:    capacity,
	}
	fifo.cond = sync.NewCond(&fifo.mutex) // Initialize condition variable
	return fifo
}

// Enqueue adds bytes to the end of the buffer. Returns an error if the buffer is full.
func (f *ByteFIFO) Enqueue(data []byte) error {
	f.mutex.Lock()
	defer f.mutex.Unlock()

	if len(f.buffer)+len(data) > f.cap {
		return errors.New("buffer overflow")
	}

	f.buffer = append(f.buffer, data...)
	f.cond.Signal() // Notify waiting goroutines that data is available
	return nil
}

// Dequeue removes and returns the first `n` bytes from the buffer (or what's left if n>len(f.buffer)).
// Returns an error if nothing is in the queue
func (f *ByteFIFO) Dequeue(n int) ([]byte, error) {
	f.mutex.Lock()
	defer f.mutex.Unlock()

	if len(f.buffer) == 0 {
		return nil, errors.New("buffer is empty")
	}
	if n > len(f.buffer) {
		n = len(f.buffer)
	}

	data := f.buffer[:n]
	f.buffer = f.buffer[n:]
	return data, nil
}

// DequeueOrWait removes and returns the first `n` bytes, waiting if the buffer is empty until data is available.
func (f *ByteFIFO) DequeueOrWait(n int) ([]byte, error) {
	f.mutex.Lock()
	defer f.mutex.Unlock()

	// Wait until enough data is available
	for len(f.buffer) < n {
		f.cond.Wait()
	}

	data := f.buffer[:n]
	f.buffer = f.buffer[n:]
	return data, nil
}

// DequeueOrWaitContext removes and returns the first `n` bytes, waiting if necessary until data is available or the context is canceled.
func (f *ByteFIFO) DequeueOrWaitContext(ctx context.Context, n int) ([]byte, error) {
	done := make(chan struct{})
	var data []byte
	var err error

	go func() {
		f.mutex.Lock()
		defer f.mutex.Unlock()
		defer close(done)

		// Wait until enough data is available
		for len(f.buffer) < n {
			select {
			case <-ctx.Done():
				err = ctx.Err()
				return
			default:
				f.cond.Wait()
			}
		}

		data = f.buffer[:n]
		f.buffer = f.buffer[n:]
	}()

	select {
	case <-done:
		return data, err
	case <-ctx.Done():
		return nil, ctx.Err()
	}
}

// Peek returns the first `n` bytes without removing them from the buffer. Returns an error if there are not enough bytes.
func (f *ByteFIFO) Peek(n int) ([]byte, error) {
	f.mutex.Lock()
	defer f.mutex.Unlock()

	if n > len(f.buffer) {
		return nil, errors.New("not enough data in buffer")
	}

	return f.buffer[:n], nil
}

// GetLen returns the current number of bytes in the buffer.
func (f *ByteFIFO) GetLen() int {
	f.mutex.Lock()
	defer f.mutex.Unlock()

	return len(f.buffer)
}

// Capacity returns the maximum capacity of the buffer.
func (f *ByteFIFO) Capacity() int {
	return f.cap
}

// *****

type StringFIFO struct {
	buffer []string   // The underlying byte slice
	mutex  sync.Mutex // Mutex for thread safety
	cond   *sync.Cond // Condition variable for signaling
}

// NewStringFIFO creates a new StringFIFO.
func NewStringFIFO() *StringFIFO {
	fifo := &StringFIFO{
		buffer: make([]string, 0),
	}
	fifo.cond = sync.NewCond(&fifo.mutex) // Initialize condition variable
	return fifo
}

// Enqueue adds a string to the end of the buffer. Returns an error if the buffer is full.
func (f *StringFIFO) Enqueue(data string) {
	f.mutex.Lock()
	defer f.mutex.Unlock()

	f.buffer = append(f.buffer, data)
	f.cond.Signal() // Notify waiting goroutines that data is available
}

// Dequeue removes and returns the first `n` bytes from the buffer (or what's left if n>len(f.buffer)).
// Returns an error if nothing is in the queue
func (f *StringFIFO) Dequeue() (string, error) {
	f.mutex.Lock()
	defer f.mutex.Unlock()

	if len(f.buffer) == 0 {
		return "", errors.New("buffer is empty")
	}

	data := f.buffer[0]
	f.buffer = f.buffer[1:]
	return data, nil
}

// DequeueOrWait removes and returns the first `n` bytes, waiting if the buffer is empty until data is available.
func (f *StringFIFO) DequeueOrWait() (string, error) {
	f.mutex.Lock()
	defer f.mutex.Unlock()

	// Wait until enough data is available
	for len(f.buffer) == 0 {
		f.cond.Wait()
	}

	data := f.buffer[0]
	f.buffer = f.buffer[1:]
	return data, nil
}

// DequeueOrWaitContext removes and returns the first `n` bytes, waiting if necessary until data is available or the context is canceled.
func (f *StringFIFO) DequeueOrWaitContext(ctx context.Context) (string, error) {
	done := make(chan struct{})
	var data string
	var err error

	go func() {
		f.mutex.Lock()
		defer f.mutex.Unlock()
		defer close(done)

		// Wait until enough data is available
		for len(f.buffer) == 0 {
			select {
			case <-ctx.Done():
				err = ctx.Err()
				return
			default:
				f.cond.Wait()
			}
		}

		data = f.buffer[0]
		f.buffer = f.buffer[1:]
	}()

	select {
	case <-done:
		return data, err
	case <-ctx.Done():
		return "", ctx.Err()
	}
}

// Peek returns the first `n` bytes without removing them from the buffer. Returns an error if there are not enough bytes.
func (f *StringFIFO) Peek() (string, error) {
	f.mutex.Lock()
	defer f.mutex.Unlock()

	if len(f.buffer) == 0 {
		return "", errors.New("not enough data in buffer")
	}

	return f.buffer[0], nil
}

// GetLen returns the current number of bytes in the buffer.
func (f *StringFIFO) GetLen() int {
	f.mutex.Lock()
	defer f.mutex.Unlock()

	return len(f.buffer)
}