package derby

import (
	"bufio"
	"errors"
	"fmt"
	"io"
	"strconv"
	"sync"
	"time"

	"go.bug.st/serial"
)

// Result represents a single lane result
type Result struct {
	Lane         int
	Time         float64
	FinishPlace  int
	FinishSymbol string
}

// RaceStatus represents the current status of a race
type RaceStatus int

const (
	StatusIdle RaceStatus = iota
	StatusRunning
	StatusFinished
)

// Event types that can be sent on the event channel
type EventType int

const (
	EventRaceStart EventType = iota
	EventLaneFinish
	EventRaceComplete
)

// Event represents a race event
type Event struct {
	Type   EventType
	Result *Result // Only populated for EventLaneFinish
}

// DerbyClock represents the connection to the derby clock device
type DerbyClock struct {
	port        serial.Port
	reader      *bufio.Reader
	eventChan   chan Event
	status      RaceStatus
	results     []*Result
	mu          sync.Mutex
	stopReading chan struct{}
}

// NewDerbyClock creates a new connection to the derby clock
func NewDerbyClock(portName string, baudRate int) (*DerbyClock, error) {
	mode := &serial.Mode{
		BaudRate: baudRate,
		DataBits: 8,
		Parity:   serial.NoParity,
		StopBits: serial.OneStopBit,
	}

	port, err := serial.Open(portName, mode)
	if err != nil {
		return nil, fmt.Errorf("failed to open serial port: %w", err)
	}

	dc := &DerbyClock{
		port:        port,
		reader:      bufio.NewReader(port),
		eventChan:   make(chan Event, 10), // Buffer for up to 10 events
		status:      StatusIdle,
		stopReading: make(chan struct{}),
	}

	// Start the reader goroutine
	go dc.readLoop()

	return dc, nil
}

// Close closes the connection to the derby clock
func (dc *DerbyClock) Close() error {
	// Signal the reading goroutine to stop
	close(dc.stopReading)

	// Close the event channel
	close(dc.eventChan)

	// Close the serial port
	return dc.port.Close()
}

// Events returns the channel for race events
func (dc *DerbyClock) Events() <-chan Event {
	return dc.eventChan
}

// Reset sends the reset command to the derby clock
func (dc *DerbyClock) Reset() error {
	dc.mu.Lock()
	defer dc.mu.Unlock()

	// Clear any previous results
	dc.results = nil
	dc.status = StatusIdle

	// Send the reset command
	_, err := dc.port.Write([]byte("R"))
	if err != nil {
		return fmt.Errorf("failed to send reset command: %w", err)
	}

	return nil
}

// ForceEnd sends the force end command to the derby clock
func (dc *DerbyClock) ForceEnd() error {
	dc.mu.Lock()
	defer dc.mu.Unlock()

	if dc.status != StatusRunning {
		return errors.New("race is not currently running")
	}

	// Send the force end command
	_, err := dc.port.Write([]byte("F"))
	if err != nil {
		return fmt.Errorf("failed to send force end command: %w", err)
	}

	return nil
}

// Status returns the current race status
func (dc *DerbyClock) Status() RaceStatus {
	dc.mu.Lock()
	defer dc.mu.Unlock()
	return dc.status
}

// Results returns a copy of the current race results
func (dc *DerbyClock) Results() []*Result {
	dc.mu.Lock()
	defer dc.mu.Unlock()

	// Make a copy of the results
	resultsCopy := make([]*Result, len(dc.results))
	for i, r := range dc.results {
		resultCopy := *r
		resultsCopy[i] = &resultCopy
	}

	return resultsCopy
}

// readLoop continuously reads from the serial port
func (dc *DerbyClock) readLoop() {
	buffer := make([]byte, 0, 256)

	for {
		select {
		case <-dc.stopReading:
			return
		default:
			// Read a single byte
			b := make([]byte, 1)
			_, err := dc.port.Read(b)
			if err != nil {
				if err != io.EOF {
					// Only log if it's not EOF
					fmt.Printf("Error reading from serial port: %v\n", err)
				}
				time.Sleep(100 * time.Millisecond)
				continue
			}

			// Add the byte to our buffer
			buffer = append(buffer, b[0])

			// Check for race start signal "C\r\n"
			if len(buffer) >= 3 && string(buffer[len(buffer)-3:]) == "C\r\n" {
				dc.mu.Lock()
				dc.status = StatusRunning
				dc.mu.Unlock()

				// Send race start event
				dc.eventChan <- Event{Type: EventRaceStart}

				// Clear the buffer
				buffer = buffer[:0]
				continue
			}

			// Check for lane result pattern (n=t.ttttc)
			// We need to look for an equals sign followed by digits, a period, more digits, and a finish character
			if b[0] == ' ' || b[0] == '\n' {
				// These characters could indicate a complete result or a separator
				// Try to extract a result from the buffer
				result := dc.tryExtractResult(buffer)
				if result != nil {
					// Send lane finish event
					dc.eventChan <- Event{
						Type:   EventLaneFinish,
						Result: result,
					}

					// If we hit a newline, this might be the end of all results
					if b[0] == '\n' {
						// Check if we should consider the race complete
						dc.mu.Lock()
						if dc.status == StatusRunning {
							dc.status = StatusFinished
							dc.mu.Unlock()

							// Send race complete event
							dc.eventChan <- Event{Type: EventRaceComplete}
						} else {
							dc.mu.Unlock()
						}

						// Clear the buffer after a newline
						buffer = buffer[:0]
					}
				}
			}
		}
	}
}

// tryExtractResult attempts to extract a lane result from the buffer
func (dc *DerbyClock) tryExtractResult(buffer []byte) *Result {
	// Convert buffer to string for easier processing
	bufStr := string(buffer)

	// Look for the pattern: n=t.ttttc
	// where n is the lane number, t.tttt is the time, and c is the finish character
	for i := 0; i < len(bufStr); i++ {
		if bufStr[i] == '=' {
			// Found an equals sign, try to extract a lane number before it
			j := i - 1
			for j >= 0 && bufStr[j] >= '0' && bufStr[j] <= '9' {
				j--
			}
			j++ // Move back to the first digit

			if j < i { // We found at least one digit
				laneStr := bufStr[j:i]

				// Now look for the time and finish character after the equals sign
				k := i + 1
				for k < len(bufStr) && (bufStr[k] == '.' || (bufStr[k] >= '0' && bufStr[k] <= '9')) {
					k++
				}

				if k < len(bufStr) && k > i+1 { // We found a time and a finish character
					timeStr := bufStr[i+1 : k]
					finishChar := bufStr[k : k+1]

					// Parse the lane number
					lane, err := strconv.Atoi(laneStr)
					if err != nil {
						continue
					}

					// Parse the time
					timeVal, err := strconv.ParseFloat(timeStr, 64)
					if err != nil {
						continue
					}

					finishPlace := 0

					switch finishChar {
					case "!":
						finishPlace = 1
					case "\"":
						finishPlace = 2
					case "#":
						finishPlace = 3
					case "$":
						finishPlace = 4
					}

					// Create and return the result
					return &Result{
						Lane:         lane,
						Time:         timeVal,
						FinishPlace:  finishPlace,
						FinishSymbol: finishChar,
					}
				}
			}
		}
	}

	return nil
}