js/rules.js

/**
 * Adaptive Tactics - Game Rules
 * Movement, attack range, hit/damage calculations, terrain modifiers
 */

import { MapData } from './models.js';

/**
 * Calculate movement range for a unit
 * Returns array of [row, col] positions the unit can move to
 */
export function calculateMoveRange(unit, map, allUnits) {
    const reachable = [];
    const visited = new Map();
    const queue = [[unit.row, unit.col, unit.mov]];

    visited.set(`${unit.row},${unit.col}`, unit.mov);

    while (queue.length > 0) {
        const [row, col, remaining] = queue.shift();

        // Add to reachable if not starting position
        if (row !== unit.row || col !== unit.col) {
            const tile = map.getTile(row, col);
            // Can only move to unoccupied tiles
            if (tile && !tile.isOccupied()) {
                reachable.push([row, col]);
            }
        }

        if (remaining <= 0) continue;

        // Check adjacent tiles
        const directions = [[-1, 0], [1, 0], [0, -1], [0, 1]];
        for (const [dr, dc] of directions) {
            const newRow = row + dr;
            const newCol = col + dc;
            const key = `${newRow},${newCol}`;

            const tile = map.getTile(newRow, newCol);
            if (!tile || !tile.isPassable()) continue;

            // Can pass through allied units but not enemies
            const occupant = tile.unit;
            if (occupant && occupant.faction !== unit.faction) continue;

            const newRemaining = remaining - 1;
            const prevRemaining = visited.get(key) ?? -1;

            if (newRemaining > prevRemaining) {
                visited.set(key, newRemaining);
                queue.push([newRow, newCol, newRemaining]);
            }
        }
    }

    return reachable;
}

/**
 * Calculate attack range from a position with a weapon
 * Returns array of [row, col] positions that can be attacked
 */
export function calculateAttackRange(row, col, weapon, map) {
    const targets = [];

    if (!weapon) return targets;

    for (let r = 1; r <= map.rows; r++) {
        for (let c = 1; c <= map.cols; c++) {
            const dist = MapData.getDistance(row, col, r, c);
            if (dist >= weapon.minRange && dist <= weapon.maxRange) {
                const tile = map.getTile(r, c);
                if (tile && tile.isPassable()) {
                    targets.push([r, c]);
                }
            }
        }
    }

    return targets;
}

/**
 * Calculate heal range from a position with a healing weapon
 * Returns array of [row, col] positions that can be healed
 */
export function calculateHealRange(row, col, weapon, map, allUnits, faction) {
    const targets = [];

    if (!weapon || !weapon.isHealingWeapon()) return targets;

    for (let r = 1; r <= map.rows; r++) {
        for (let c = 1; c <= map.cols; c++) {
            const dist = MapData.getDistance(row, col, r, c);
            if (dist >= weapon.minRange && dist <= weapon.maxRange) {
                const tile = map.getTile(r, c);
                if (tile && tile.unit && tile.unit.faction === faction && tile.unit.hp < tile.unit.maxHp) {
                    targets.push([r, c]);
                }
            }
        }
    }

    return targets;
}

/**
 * Calculate displayed hit chance
 * Formula: weapon_hit + skill × 2
 */
export function calculateDisplayedHit(attacker, weapon) {
    return weapon.hit + (attacker.skill * 2);
}

/**
 * Calculate displayed avoid
 * Formula: speed × 2 + terrain_avoid
 */
export function calculateDisplayedAvoid(defender, terrainAvoid = 0) {
    return (defender.speed * 2) + terrainAvoid;
}

/**
 * Calculate actual hit chance
 * Formula: displayed_hit - displayed_avoid
 */
export function calculateHitChance(attacker, defender, weapon, terrainAvoid = 0) {
    const hit = calculateDisplayedHit(attacker, weapon);
    const avoid = calculateDisplayedAvoid(defender, terrainAvoid);
    return Math.max(0, Math.min(100, hit - avoid));
}

/**
 * 2RN hit check (average of two random rolls)
 * This makes displayed hit rates feel more accurate
 */
export function rollHit(hitChance) {
    const roll1 = Math.random() * 100;
    const roll2 = Math.random() * 100;
    const avgRoll = (roll1 + roll2) / 2;
    return avgRoll < hitChance;
}

/**
 * Calculate damage
 * Physical: power + weapon_might - defender_def
 * Magic: power + weapon_might - defender_res
 */
export function calculateDamage(attacker, defender, weapon, terrainDef = 0) {
    const might = attacker.power + weapon.might;
    let defense;

    if (weapon.kind === 'magic') {
        defense = defender.res;
    } else {
        defense = defender.def + terrainDef;
    }

    return Math.max(0, might - defense);
}

/**
 * Check if attacker can double (speed gap >= 4)
 */
export function canDouble(attacker, defender, speedGap = 4) {
    return attacker.speed >= defender.speed + speedGap;
}

/**
 * Check if defender can counterattack
 * Defender can counter if their equipped weapon can reach the attacker's range
 */
export function canCounter(attacker, defender, distance) {
    const defenderWeapon = defender.getEquippedWeapon();
    if (!defenderWeapon) return false;
    if (defenderWeapon.isHealingWeapon()) return false;
    return defenderWeapon.canReach(distance);
}

/**
 * Get terrain avoid bonus for a tile
 */
export function getTerrainAvoid(tile) {
    if (!tile) return 0;
    return tile.getAvoidBonus();
}

/**
 * Get terrain defense bonus for a tile
 */
export function getTerrainDef(tile) {
    if (!tile) return 0;
    return tile.getDefBonus();
}

/**
 * Calculate full combat preview
 */
export function calculateCombatPreview(attacker, defender, map, gameRules) {
    const attackerWeapon = attacker.getEquippedWeapon();
    const defenderWeapon = defender.getEquippedWeapon();
    const distance = MapData.getDistance(attacker.row, attacker.col, defender.row, defender.col);
    const defenderTile = map.getTile(defender.row, defender.col);

    const terrainAvoid = getTerrainAvoid(defenderTile);
    const terrainDef = getTerrainDef(defenderTile);

    const speedGap = gameRules?.double_speed_gap ?? 4;

    const preview = {
        attacker: {
            name: attacker.name,
            hp: attacker.hp,
            damage: 0,
            hit: 0,
            doubles: false
        },
        defender: {
            name: defender.name,
            hp: defender.hp,
            damage: 0,
            hit: 0,
            doubles: false,
            canCounter: false
        }
    };

    // Attacker stats
    if (attackerWeapon) {
        preview.attacker.damage = calculateDamage(attacker, defender, attackerWeapon, terrainDef);
        preview.attacker.hit = calculateHitChance(attacker, defender, attackerWeapon, terrainAvoid);
        preview.attacker.doubles = canDouble(attacker, defender, speedGap);
    }

    // Defender counter stats
    const defCanCounter = canCounter(attacker, defender, distance);
    preview.defender.canCounter = defCanCounter;

    if (defCanCounter && defenderWeapon) {
        const attackerTile = map.getTile(attacker.row, attacker.col);
        const attackerTerrainAvoid = getTerrainAvoid(attackerTile);
        const attackerTerrainDef = getTerrainDef(attackerTile);

        preview.defender.damage = calculateDamage(defender, attacker, defenderWeapon, attackerTerrainDef);
        preview.defender.hit = calculateHitChance(defender, attacker, defenderWeapon, attackerTerrainAvoid);
        preview.defender.doubles = canDouble(defender, attacker, speedGap);
    }

    return preview;
}