// Command acb-mapgen generates symmetric maps for AI Code Battle.
package main

import (
	"encoding/json"
	"flag"
	"fmt"
	"math"
	"math/rand"
	"os"
	"time"
)

// Map represents a generated map.
type Map struct {
	ID          string     `json:"id"`
	Players     int        `json:"players"`
	Rows        int        `json:"rows"`
	Cols        int        `json:"cols"`
	WallDensity float64    `json:"wall_density"`
	Walls       []Position `json:"walls"`
	Cores       []Core     `json:"cores"`
	EnergyNodes []Position `json:"energy_nodes"`
	Generated   time.Time  `json:"generated"`
}

// Position represents a grid coordinate.
type Position struct {
	Row int `json:"row"`
	Col int `json:"col"`
}

// Core represents a spawn point.
type Core struct {
	Position Position `json:"position"`
	Owner    int      `json:"owner"`
}

func main() {
	// Command-line flags
	players := flag.Int("players", 2, "Number of players (2, 3, 4, or 6)")
	rows := flag.Int("rows", 40, "Grid rows")
	cols := flag.Int("cols", 40, "Grid columns")
	wallDensity := flag.Float64("wall-density", 0.15, "Wall density (0.0-0.3)")
	energyNodes := flag.Int("energy-nodes", 20, "Energy nodes")
	seed := flag.Int64("seed", time.Now().UnixNano(), "Random seed")
	output := flag.String("output", "", "Output file (default: stdout)")
	maxAttempts := flag.Int("max-attempts", 100, "Max attempts to generate a connected map")
	skirmish := flag.Bool("skirmish", false, "Generate a skirmish map (32x32, higher density)")
	help := flag.Bool("help", false, "Show help")

	flag.Usage = func() {
		fmt.Fprintf(flag.CommandLine.Output(), "Usage: acb-mapgen [options]\n\n")
		fmt.Fprintf(flag.CommandLine.Output(), "Generate a symmetric map for AI Code Battle.\n\n")
		fmt.Fprintf(flag.CommandLine.Output(), "The generator ensures all passable tiles are reachable from\n")
		fmt.Fprintf(flag.CommandLine.Output(), "any core (full connectivity guarantee).\n\n")
		fmt.Fprintf(flag.CommandLine.Output(), "Symmetry types:\n")
		fmt.Fprintf(flag.CommandLine.Output(), "  2 players: 180° rotational\n")
		fmt.Fprintf(flag.CommandLine.Output(), "  3 players: 120° rotational\n")
		fmt.Fprintf(flag.CommandLine.Output(), "  4 players: 90° rotational\n")
		fmt.Fprintf(flag.CommandLine.Output(), "  6 players: 60° rotational\n\n")
		fmt.Fprintf(flag.CommandLine.Output(), "Map presets:\n")
		fmt.Fprintf(flag.CommandLine.Output(), "  -skirmish    Small dense map (32x32, 0.20 wall density, 15 energy)\n\n")
		fmt.Fprintf(flag.CommandLine.Output(), "Options:\n")
		flag.PrintDefaults()
	}

	flag.Parse()

	if *help {
		flag.Usage()
		os.Exit(0)
	}

	// Apply skirmish preset if requested
	if *skirmish {
		*rows = 32
		*cols = 32
		*wallDensity = 0.20
		*energyNodes = 15
	}

	// Validate player count
	validPlayers := map[int]bool{2: true, 3: true, 4: true, 6: true}
	if !validPlayers[*players] {
		fmt.Fprintf(os.Stderr, "Error: invalid player count %d (must be 2, 3, 4, or 6)\n", *players)
		os.Exit(1)
	}

	// Validate wall density
	if *wallDensity < 0.05 || *wallDensity > 0.30 {
		fmt.Fprintf(os.Stderr, "Error: wall density must be between 0.05 and 0.30\n")
		os.Exit(1)
	}

	// Generate map with connectivity validation
	rng := rand.New(rand.NewSource(*seed))
	m := EnsureConnectivity(*players, *rows, *cols, *wallDensity, *energyNodes, rng, *maxAttempts)
	if m == nil {
		fmt.Fprintf(os.Stderr, "Error: failed to generate a connected map after %d attempts\n", *maxAttempts)
		fmt.Fprintf(os.Stderr, "Try reducing wall density or increasing max-attempts\n")
		os.Exit(1)
	}

	// Generate map ID with skirmish prefix if applicable
	if *skirmish {
		m.ID = generateMapIDWithPrefix(rng, "skirmish")
	} else {
		m.ID = generateMapID(rng)
	}
	m.Generated = time.Now().UTC()

	// Output
	data, err := json.MarshalIndent(m, "", "  ")
	if err != nil {
		fmt.Fprintf(os.Stderr, "Error: failed to marshal map: %v\n", err)
		os.Exit(1)
	}

	if *output != "" {
		if err := os.WriteFile(*output, data, 0644); err != nil {
			fmt.Fprintf(os.Stderr, "Error: failed to write file: %v\n", err)
			os.Exit(1)
		}
		fmt.Printf("Map written to %s\n", *output)
	} else {
		fmt.Println(string(data))
	}
}

func generateMapID(rng *rand.Rand) string {
	return generateMapIDWithPrefix(rng, "map")
}

func generateMapIDWithPrefix(rng *rand.Rand, prefix string) string {
	const chars = "abcdefghijklmnopqrstuvwxyz0123456789"
	b := make([]byte, 8)
	for i := range b {
		b[i] = chars[rng.Intn(len(chars))]
	}
	return prefix + "_" + string(b)
}

func generateMap(numPlayers, rows, cols int, wallDensity float64, numEnergyNodes int, rng *rand.Rand) *Map {
	m := &Map{
		Players:     numPlayers,
		Rows:        rows,
		Cols:        cols,
		WallDensity: wallDensity,
		Walls:       make([]Position, 0),
		Cores:       make([]Core, 0),
		EnergyNodes: make([]Position, 0),
	}

	centerRow := rows / 2
	centerCol := cols / 2

	// Helper to wrap position
	wrap := func(r, c int) Position {
		r = ((r % rows) + rows) % rows
		c = ((c % cols) + cols) % cols
		return Position{Row: r, Col: c}
	}

		// Generate cores with rotational symmetry.
		// Per plan §3.7.1: zone forces combat, spawn radius ensures bots start outside final zone.
		// Target: 65-80% combat density for 2-player matches.
		//
		// For 2 players: 30% spawn radius (~6 tiles from center, ~12 tiles apart on 40x40)
		//   - Outside 5-tile attack radius, zone forces contact over time
		//   - Increased from 15% to prevent immediate mutual destruction at spawn
		//   - Zone shrink (1 tile/turn from turn 10) forces bots toward center for combat
		// For 3+ players: 15% spawn radius (~4 tiles from center, ~8 tiles apart on 50x50)
	var radius float64
	if numPlayers == 2 {
		radius = 0.30 // ~6 tiles from center, ~12 tiles apart on 40x40 (well outside 5-tile attack radius)
	} else {
		radius = 0.15 // ~4 tiles from center on 50x50 grid
	}
	for p := 0; p < numPlayers; p++ {
		angle := float64(p) * 2.0 * math.Pi / float64(numPlayers)
		r := centerRow + int(float64(centerRow)*radius*math.Cos(angle))
		c := centerCol + int(float64(centerCol)*radius*math.Sin(angle))
		m.Cores = append(m.Cores, Core{
			Position: wrap(r, c),
			Owner:    p,
		})
	}

	// Generate energy nodes with rotational symmetry.
	// Tiered radius distribution biases toward center to force contested energy:
	// - 30% central (0.05-0.20): contested central zone
	// - 40% mid (0.20-0.40): mid-zone
	// - 30% home (0.40-0.60): home zone
	nodesPerSector := numEnergyNodes / numPlayers
	usedPositions := make(map[Position]bool)

	// Mark core positions as used
	for _, c := range m.Cores {
		usedPositions[c.Position] = true
	}

	for i := 0; i < nodesPerSector; i++ {
		for attempt := 0; attempt < 100; attempt++ {
			angle := rng.Float64() * 2.0 * math.Pi / float64(numPlayers)
			// Tiered radius: bias toward center to force contested energy collection.
			// 30% central (forces both players to midfield), 40% mid, 30% home.
			var radius float64
			switch {
			case i < nodesPerSector*3/10:
				radius = 0.05 + rng.Float64()*0.15 // 0.05–0.20: contested central zone
			case i < nodesPerSector*7/10:
				radius = 0.20 + rng.Float64()*0.20 // 0.20–0.40: mid-zone
			default:
				radius = 0.40 + rng.Float64()*0.20 // 0.40–0.60: home zone
			}
			r := centerRow + int(float64(centerRow)*radius*math.Cos(angle))
			c := centerCol + int(float64(centerCol)*radius*math.Sin(angle))
			pos := wrap(r, c)

			if !usedPositions[pos] {
				usedPositions[pos] = true
				// Mirror for all players
				for p := 0; p < numPlayers; p++ {
					rotAngle := angle + float64(p)*2.0*math.Pi/float64(numPlayers)
					rr := centerRow + int(float64(centerRow)*radius*math.Cos(rotAngle))
					rc := centerCol + int(float64(centerCol)*radius*math.Sin(rotAngle))
					m.EnergyNodes = append(m.EnergyNodes, wrap(rr, rc))
				}
				break
			}
		}
	}

	// Generate walls using cellular automata for natural-looking structures.
	// Algorithm: seed the full grid, run automata to form clusters,
	// enforce rotational symmetry by copying sector 0 to all sectors,
	// then thin to target density.

	// Build a set of protected positions (cores, energy nodes, and neighbors)
	protected := make(map[Position]bool)
	clearRadius := 3
	for _, core := range m.Cores {
		for dr := -clearRadius; dr <= clearRadius; dr++ {
			for dc := -clearRadius; dc <= clearRadius; dc++ {
				protected[wrap(core.Position.Row+dr, core.Position.Col+dc)] = true
			}
		}
	}
	for _, en := range m.EnergyNodes {
		for dr := -1; dr <= 1; dr++ {
			for dc := -1; dc <= 1; dc++ {
				protected[wrap(en.Row+dr, en.Col+dc)] = true
			}
		}
	}

	// Step 1: Seed full grid at ~40% random fill
	grid := make([][]bool, rows)
	for r := 0; r < rows; r++ {
		grid[r] = make([]bool, cols)
		for c := 0; c < cols; c++ {
			if !protected[Position{Row: r, Col: c}] && rng.Float64() < 0.40 {
				grid[r][c] = true
			}
		}
	}

	// Step 2: Run cellular automata smoothing (4 iterations)
	// Rule: birth at >= 5 wall neighbors, survive at >= 4
	for iter := 0; iter < 4; iter++ {
		newGrid := make([][]bool, rows)
		for r := 0; r < rows; r++ {
			newGrid[r] = make([]bool, cols)
			for c := 0; c < cols; c++ {
				if protected[Position{Row: r, Col: c}] {
					continue
				}
				neighbors := 0
				for ndr := -1; ndr <= 1; ndr++ {
					for ndc := -1; ndc <= 1; ndc++ {
						if ndr == 0 && ndc == 0 {
							continue
						}
						nr := ((r+ndr)%rows + rows) % rows
						nc := ((c+ndc)%cols + cols) % cols
						if grid[nr][nc] {
							neighbors++
						}
					}
				}
				if grid[r][c] {
					newGrid[r][c] = neighbors >= 4
				} else {
					newGrid[r][c] = neighbors >= 5
				}
			}
		}
		grid = newGrid
	}

	// Step 3: Enforce rotational symmetry by reading from sector 0
	sectorAngle := 2.0 * math.Pi / float64(numPlayers)
	symGrid := make([][]bool, rows)
	for r := 0; r < rows; r++ {
		symGrid[r] = make([]bool, cols)
		for c := 0; c < cols; c++ {
			if protected[Position{Row: r, Col: c}] {
				continue
			}
			// Find the canonical position in sector 0
			dr := float64(r) - float64(centerRow)
			dc := float64(c) - float64(centerCol)
			angle := math.Atan2(dc, dr)
			if angle < 0 {
				angle += 2.0 * math.Pi
			}
			sector := int(angle / sectorAngle)
			if sector >= numPlayers {
				sector = numPlayers - 1
			}

			if sector == 0 {
				symGrid[r][c] = grid[r][c]
			} else {
				// Rotate back to sector 0
				rotAngle := -float64(sector) * sectorAngle
				cosA := math.Cos(rotAngle)
				sinA := math.Sin(rotAngle)
				srcR := int(math.Round(float64(centerRow) + dr*cosA - dc*sinA))
				srcC := int(math.Round(float64(centerCol) + dr*sinA + dc*cosA))
				sr := ((srcR % rows) + rows) % rows
				sc := ((srcC % cols) + cols) % cols
				symGrid[r][c] = grid[sr][sc]
			}
		}
	}

	// Step 4: Thin to target density if needed
	totalTiles := rows * cols
	targetWalls := int(float64(totalTiles) * wallDensity)
	var wallPositions []Position
	for r := 0; r < rows; r++ {
		for c := 0; c < cols; c++ {
			if symGrid[r][c] {
				wallPositions = append(wallPositions, Position{Row: r, Col: c})
			}
		}
	}
	if len(wallPositions) > targetWalls {
		rng.Shuffle(len(wallPositions), func(i, j int) {
			wallPositions[i], wallPositions[j] = wallPositions[j], wallPositions[i]
		})
		wallPositions = wallPositions[:targetWalls]
	}

	m.Walls = wallPositions

	return m
}