import { ref, computed, onMounted, onUnmounted } from 'vue';

export function usePetSystem() {
    // --- State ---
    const stage = ref('egg'); // egg, baby, adult
    const state = ref('idle'); // idle, sleep, eating, sick, dead, refuse

    // --- Stats ---
    const stats = ref({
        hunger: 100,    // 0-100 (0 = Starving)
        happiness: 100, // 0-100 (0 = Depressed)
        health: 100,    // 0-100 (0 = Sick risk)
        weight: 500,    // grams
        age: 0,         // days
        poopCount: 0    // Number of poops on screen
    });

    // --- Internal Timers ---
    let gameLoopId = null;
    const TICK_RATE = 3000; // 3 seconds per tick

    const isCleaning = ref(false);

    // --- Actions ---

    function feed() {
        if (state.value === 'sleep' || state.value === 'dead' || stage.value === 'egg' || isCleaning.value) return false;

        if (state.value === 'sick' || stats.value.hunger >= 90) {
            // Refuse food if sick or full
            triggerState('refuse', 2000);
            return false;
        }

        // Eat
        triggerState('eating', 3000); // Animation duration
        stats.value.hunger = Math.min(100, stats.value.hunger + 20);
        stats.value.weight += 50;

        // Chance to poop after eating (降低機率)
        if (Math.random() < 0.15) { // 從 0.3 降到 0.15
            setTimeout(() => {
                if (stats.value.poopCount < 4) {
                    stats.value.poopCount++;
                }
            }, 4000);
        }

        return true;
    }

    function play() {
        if (state.value !== 'idle' || stage.value === 'egg' || isCleaning.value) return false;

        stats.value.happiness = Math.min(100, stats.value.happiness + 15);
        stats.value.weight -= 10; // Exercise burns calories
        stats.value.hunger = Math.max(0, stats.value.hunger - 5);
        return true;
    }

    function clean() {
        if (stats.value.poopCount > 0 && !isCleaning.value) {
            isCleaning.value = true;

            // Delay removal for animation
            setTimeout(() => {
                stats.value.poopCount = 0;
                stats.value.happiness += 10;
                isCleaning.value = false;
            }, 2000); // 2 seconds flush animation

            return true;
        }
        return false;
    }

    function sleep() {
        if (isCleaning.value) return;

        if (state.value === 'idle') {
            state.value = 'sleep';
        } else if (state.value === 'sleep') {
            state.value = 'idle'; // Wake up
        }
    }

    // --- Game Loop ---
    function tick() {
        if (state.value === 'dead' || stage.value === 'egg') return;

        // Decrease stats naturally
        // 目標：飢餓值約 30-60 分鐘下降 10%，快樂值約 20-40 分鐘下降 10%
        // TICK_RATE = 3000ms (3秒), 600 ticks = 30分鐘
        // 飢餓值每 tick -0.05 → 600 ticks = -30 (30分鐘下降30%)
        // 快樂值每 tick -0.08 → 600 ticks = -48 (30分鐘下降48%)

        if (state.value !== 'sleep') {
            stats.value.hunger = Math.max(0, stats.value.hunger - 0.05);
            stats.value.happiness = Math.max(0, stats.value.happiness - 0.08);
        } else {
            // Slower decay when sleeping (約 1/3 速度)
            stats.value.hunger = Math.max(0, stats.value.hunger - 0.015);
            stats.value.happiness = Math.max(0, stats.value.happiness - 0.025);
        }

        // Random poop generation (更低的機率：約 0.5% per tick)
        // 平均約每 200 ticks = 10 分鐘拉一次
        if (state.value !== 'sleep' && Math.random() < 0.005 && stats.value.poopCount < 4 && !isCleaning.value) {
            stats.value.poopCount++;
        }

        // Health Logic (更溫和的健康下降)
        // 便便影響健康：每個便便每 tick -0.1 health
        if (stats.value.poopCount > 0) {
            stats.value.health = Math.max(0, stats.value.health - (0.1 * stats.value.poopCount));
        }

        // 飢餓影響健康：飢餓值低於 20 時開始影響健康
        if (stats.value.hunger < 20) {
            const hungerPenalty = (20 - stats.value.hunger) * 0.02; // 飢餓越嚴重，扣越多
            stats.value.health = Math.max(0, stats.value.health - hungerPenalty);
        }

        // 不開心影響健康：快樂值低於 20 時開始影響健康（較輕微）
        if (stats.value.happiness < 20) {
            const happinessPenalty = (20 - stats.value.happiness) * 0.01;
            stats.value.health = Math.max(0, stats.value.health - happinessPenalty);
        }

        // Sickness Check (更低的生病機率)
        if (stats.value.health < 30 && state.value !== 'sick') {
            if (Math.random() < 0.1) { // 從 0.3 降到 0.1
                state.value = 'sick';
            }
        }

        // Health Recovery (健康值可以緩慢恢復)
        // 如果沒有便便、飢餓值和快樂值都高，健康值會緩慢恢復
        if (stats.value.poopCount === 0 && stats.value.hunger > 50 && stats.value.happiness > 50 && stats.value.health < 100 && state.value !== 'sick') {
            stats.value.health = Math.min(100, stats.value.health + 0.05);
        }

        // Death Check (移除死亡機制，依照之前的討論)
        // if (stats.value.health === 0) {
        //     state.value = 'dead';
        // }

        // Evolution / Growth (Simple Age increment)
        // In a real game, 1 day might be 24h, here maybe every 100 ticks?
        // For now, let's just say age increases slowly.
    }

    // --- Helpers ---
    function triggerState(tempState, duration) {
        const previousState = state.value;
        state.value = tempState;
        setTimeout(() => {
            if (state.value === tempState) { // Only revert if state hasn't changed again
                state.value = previousState === 'sleep' ? 'idle' : 'idle';
            }
        }, duration);
    }

    function hatchEgg() {
        if (stage.value === 'egg') {
            stage.value = 'baby'; // or 'adult' for now since we only have that sprite
            // Let's map 'baby' to our 'adult' sprite for now, or just use 'adult'
            stage.value = 'adult';
            state.value = 'idle';
            stats.value.hunger = 50;
            stats.value.happiness = 50;
            stats.value.health = 100;
            stats.value.poopCount = 0;
            isCleaning.value = false;
        }
    }

    function reset() {
        stage.value = 'egg';
        state.value = 'idle';
        isCleaning.value = false;
        stats.value = {
            hunger: 100,
            happiness: 100,
            health: 100,
            weight: 500,
            age: 0,
            poopCount: 0
        };
    }

    // --- Lifecycle ---
    onMounted(() => {
        gameLoopId = setInterval(tick, TICK_RATE);
    });

    onUnmounted(() => {
        if (gameLoopId) clearInterval(gameLoopId);
    });

    return {
        stage,
        state,
        stats,
        isCleaning,
        feed,
        play,
        clean,
        sleep,
        hatchEgg,
        reset
    };
}