package game

import (
	"bufio"
	"fmt"
	"log"
	"math/rand"
	"os"
	"sync"

	"github.com/google/uuid"
	"github.com/mdiluz/rove/pkg/atlas"
	"github.com/mdiluz/rove/pkg/bearing"
	"github.com/mdiluz/rove/pkg/objects"
	"github.com/mdiluz/rove/pkg/vector"
)

// World describes a self contained universe and everything in it
type World struct {
	// Rovers is a id->data map of all the rovers in the game
	Rovers map[string]Rover `json:"rovers"`

	// Atlas represends the world map of chunks and tiles
	Atlas atlas.Atlas `json:"atlas"`

	// Mutex to lock around all world operations
	worldMutex sync.RWMutex

	// Commands is the set of currently executing command streams per rover
	CommandQueue map[string]CommandStream `json:"commands"`

	// Incoming represents the set of commands to add to the queue at the end of the current tick
	Incoming map[string]CommandStream `json:"incoming"`

	// Mutex to lock around command operations
	cmdMutex sync.RWMutex

	// Set of possible words to use for names
	words []string
}

var wordsFile = os.Getenv("WORDS_FILE")

// NewWorld creates a new world object
func NewWorld(chunkSize int) *World {

	// Try and load the words file
	var lines []string
	if file, err := os.Open(wordsFile); err != nil {
		log.Printf("Couldn't read words file [%s], running without words: %s\n", wordsFile, err)
	} else {
		defer file.Close()
		scanner := bufio.NewScanner(file)
		for scanner.Scan() {
			lines = append(lines, scanner.Text())
		}
		if scanner.Err() != nil {
			log.Printf("Failure during word file scan: %s\n", scanner.Err())
		}
	}

	return &World{
		Rovers:       make(map[string]Rover),
		CommandQueue: make(map[string]CommandStream),
		Incoming:     make(map[string]CommandStream),
		Atlas:        atlas.NewAtlas(chunkSize),
		words:        lines,
	}
}

// SpawnRover adds an rover to the game
func (w *World) SpawnRover() (string, error) {
	w.worldMutex.Lock()
	defer w.worldMutex.Unlock()

	// Initialise the rover
	rover := Rover{
		Range:            4.0,
		Integrity:        10,
		MaximumIntegrity: 10,
		Capacity:         10,
		Name:             uuid.New().String(),
	}

	// Assign a random name if we have words
	if len(w.words) > 0 {
		for {
			// Loop until we find a unique name
			name := fmt.Sprintf("%s-%s", w.words[rand.Intn(len(w.words))], w.words[rand.Intn(len(w.words))])
			if _, ok := w.Rovers[name]; !ok {
				rover.Name = name
				break
			}
		}
	}

	// Spawn in a random place near the origin
	rover.Pos = vector.Vector{
		X: w.Atlas.ChunkSize/2 - rand.Intn(w.Atlas.ChunkSize),
		Y: w.Atlas.ChunkSize/2 - rand.Intn(w.Atlas.ChunkSize),
	}

	// Seach until we error (run out of world)
	for {
		_, obj := w.Atlas.QueryPosition(rover.Pos)
		if !obj.IsBlocking() {
			break
		} else {
			// Try and spawn to the east of the blockage
			rover.Pos.Add(vector.Vector{X: 1, Y: 0})
		}

	}

	log.Printf("Spawned rover at %+v\n", rover.Pos)

	// Append the rover to the list
	w.Rovers[rover.Name] = rover

	return rover.Name, nil
}

// GetRover gets a specific rover by name
func (w *World) GetRover(rover string) (Rover, error) {
	w.worldMutex.RLock()
	defer w.worldMutex.RUnlock()

	i, ok := w.Rovers[rover]
	if !ok {
		return Rover{}, fmt.Errorf("Failed to find rover with name: %s", rover)
	}
	return i, nil
}

// DestroyRover Removes an rover from the game
func (w *World) DestroyRover(rover string) error {
	w.worldMutex.Lock()
	defer w.worldMutex.Unlock()

	_, ok := w.Rovers[rover]
	if !ok {
		return fmt.Errorf("no rover matching id")
	}

	delete(w.Rovers, rover)
	return nil
}

// RoverPosition returns the position of the rover
func (w *World) RoverPosition(rover string) (vector.Vector, error) {
	w.worldMutex.RLock()
	defer w.worldMutex.RUnlock()

	i, ok := w.Rovers[rover]
	if !ok {
		return vector.Vector{}, fmt.Errorf("no rover matching id")
	}
	return i.Pos, nil
}

// SetRoverPosition sets the position of the rover
func (w *World) SetRoverPosition(rover string, pos vector.Vector) error {
	w.worldMutex.Lock()
	defer w.worldMutex.Unlock()

	i, ok := w.Rovers[rover]
	if !ok {
		return fmt.Errorf("no rover matching id")
	}

	i.Pos = pos
	w.Rovers[rover] = i
	return nil
}

// RoverInventory returns the inventory of a requested rover
func (w *World) RoverInventory(rover string) ([]objects.Object, error) {
	w.worldMutex.RLock()
	defer w.worldMutex.RUnlock()

	i, ok := w.Rovers[rover]
	if !ok {
		return nil, fmt.Errorf("no rover matching id")
	}
	return i.Inventory, nil
}

// WarpRover sets an rovers position
func (w *World) WarpRover(rover string, pos vector.Vector) error {
	w.worldMutex.Lock()
	defer w.worldMutex.Unlock()

	i, ok := w.Rovers[rover]
	if !ok {
		return fmt.Errorf("no rover matching id")
	}
	// Nothing to do if these positions match
	if i.Pos == pos {
		return nil
	}

	// Check the tile is not blocked
	_, obj := w.Atlas.QueryPosition(pos)
	if obj.IsBlocking() {
		return fmt.Errorf("can't warp rover to occupied tile, check before warping")
	}

	i.Pos = pos
	w.Rovers[rover] = i
	return nil
}

// MoveRover attempts to move a rover in a specific direction
func (w *World) MoveRover(rover string, b bearing.Bearing) (vector.Vector, error) {
	w.worldMutex.Lock()
	defer w.worldMutex.Unlock()

	i, ok := w.Rovers[rover]
	if !ok {
		return vector.Vector{}, fmt.Errorf("no rover matching id")
	}
	// Try the new move position
	newPos := i.Pos.Added(b.Vector())

	// Get the tile and verify it's empty
	_, obj := w.Atlas.QueryPosition(newPos)
	if !obj.IsBlocking() {
		// Perform the move
		i.Pos = newPos
		w.Rovers[rover] = i
	} else {
		// If it is a blocking tile, reduce the rover integrity
		i.Integrity = i.Integrity - 1
		if i.Integrity == 0 {
			// TODO: The rover needs to be left dormant with the player
		} else {
			w.Rovers[rover] = i
		}
	}

	return i.Pos, nil
}

// RoverStash will stash an item at the current rovers position
func (w *World) RoverStash(rover string) (objects.Type, error) {
	w.worldMutex.Lock()
	defer w.worldMutex.Unlock()

	r, ok := w.Rovers[rover]
	if !ok {
		return objects.None, fmt.Errorf("no rover matching id")
	}

	// Can't pick up when full
	if len(r.Inventory) >= r.Capacity {
		return objects.None, nil
	}

	_, obj := w.Atlas.QueryPosition(r.Pos)
	if !obj.IsStashable() {
		return objects.None, nil
	}

	r.Inventory = append(r.Inventory, obj)
	w.Rovers[rover] = r
	w.Atlas.SetObject(r.Pos, objects.Object{Type: objects.None})
	return obj.Type, nil
}

// RadarFromRover can be used to query what a rover can currently see
func (w *World) RadarFromRover(rover string) (radar []byte, objs []byte, err error) {
	w.worldMutex.RLock()
	defer w.worldMutex.RUnlock()

	r, ok := w.Rovers[rover]
	if !ok {
		err = fmt.Errorf("no rover matching id")
		return
	}

	// The radar should span in range direction on each axis, plus the row/column the rover is currently on
	radarSpan := (r.Range * 2) + 1
	roverPos := r.Pos

	// Get the radar min and max values
	radarMin := vector.Vector{
		X: roverPos.X - r.Range,
		Y: roverPos.Y - r.Range,
	}
	radarMax := vector.Vector{
		X: roverPos.X + r.Range,
		Y: roverPos.Y + r.Range,
	}

	// Gather up all tiles within the range
	radar = make([]byte, radarSpan*radarSpan)
	objs = make([]byte, radarSpan*radarSpan)
	for j := radarMin.Y; j <= radarMax.Y; j++ {
		for i := radarMin.X; i <= radarMax.X; i++ {
			q := vector.Vector{X: i, Y: j}

			tile, obj := w.Atlas.QueryPosition(q)

			// Get the position relative to the bottom left of the radar
			relative := q.Added(radarMin.Negated())
			index := relative.X + relative.Y*radarSpan
			radar[index] = tile
			objs[index] = byte(obj.Type)
		}
	}

	// Add all rovers to the radar
	for _, r := range w.Rovers {
		// If the rover is in range
		dist := r.Pos.Added(roverPos.Negated())
		dist = dist.Abs()

		if dist.X <= r.Range && dist.Y <= r.Range {
			relative := r.Pos.Added(radarMin.Negated())
			index := relative.X + relative.Y*radarSpan
			objs[index] = byte(objects.Rover)
		}
	}

	return radar, objs, nil
}

// Enqueue will queue the commands given
func (w *World) Enqueue(rover string, commands ...Command) error {

	// First validate the commands
	for _, c := range commands {
		switch c.Command {
		case CommandMove:
			if _, err := bearing.FromString(c.Bearing); err != nil {
				return fmt.Errorf("unknown bearing: %s", c.Bearing)
			}
		case CommandStash:
		case CommandRepair:
			// Nothing to verify
		default:
			return fmt.Errorf("unknown command: %s", c.Command)
		}
	}

	// Lock our commands edit
	w.cmdMutex.Lock()
	defer w.cmdMutex.Unlock()

	// Append the commands to the incoming set
	if cmds, ok := w.Incoming[rover]; ok {
		w.Incoming[rover] = append(cmds, commands...)
	} else {
		w.Incoming[rover] = commands
	}

	return nil
}

// EnqueueAllIncoming will enqueue the incoming commands
func (w *World) EnqueueAllIncoming() {
	// Add any incoming commands from this tick and clear that queue
	for id, incoming := range w.Incoming {
		commands := w.CommandQueue[id]
		commands = append(commands, incoming...)
		w.CommandQueue[id] = commands
	}
	w.Incoming = make(map[string]CommandStream)
}

// ExecuteCommandQueues will execute any commands in the current command queue
func (w *World) ExecuteCommandQueues() {
	w.cmdMutex.Lock()
	defer w.cmdMutex.Unlock()

	// Iterate through all the current commands
	for rover, cmds := range w.CommandQueue {
		if len(cmds) != 0 {
			// Extract the first command in the queue
			c := cmds[0]
			w.CommandQueue[rover] = cmds[1:]

			// Execute the command
			if err := w.ExecuteCommand(&c, rover); err != nil {
				log.Println(err)
				// TODO: Report this error somehow
			}

		} else {
			// Clean out the empty entry
			delete(w.CommandQueue, rover)
		}
	}

	// Add any incoming commands from this tick and clear that queue
	w.EnqueueAllIncoming()
}

// ExecuteCommand will execute a single command
func (w *World) ExecuteCommand(c *Command, rover string) (err error) {
	log.Printf("Executing command: %+v for %s\n", *c, rover)

	switch c.Command {
	case CommandMove:
		if dir, err := bearing.FromString(c.Bearing); err != nil {
			return err
		} else if _, err := w.MoveRover(rover, dir); err != nil {
			return err
		}

	case CommandStash:
		if _, err := w.RoverStash(rover); err != nil {
			return err
		}

	case CommandRepair:
		r, err := w.GetRover(rover)
		if err != nil {
			return err
		}
		// Consume an inventory item to repair if possible
		if len(r.Inventory) > 0 && r.Integrity < r.MaximumIntegrity {
			r.Inventory = r.Inventory[:len(r.Inventory)-1]
			r.Integrity = r.Integrity + 1
			w.Rovers[rover] = r
		}
	default:
		return fmt.Errorf("unknown command: %s", c.Command)
	}

	return
}

// RLock read locks the world
func (w *World) RLock() {
	w.worldMutex.RLock()
	w.cmdMutex.RLock()
}

// RUnlock read unlocks the world
func (w *World) RUnlock() {
	w.worldMutex.RUnlock()
	w.cmdMutex.RUnlock()
}

// Lock locks the world
func (w *World) Lock() {
	w.worldMutex.Lock()
	w.cmdMutex.Lock()
}

// Unlock unlocks the world
func (w *World) Unlock() {
	w.worldMutex.Unlock()
	w.cmdMutex.Unlock()
}