class QuestSystem {
    constructor(scene) {
        this.scene = scene;

        // Quest Definitions
        this.questDB = {
            'q1_start': {
                id: 'q1_start',
                title: 'Survival Basics',
                description: 'Collect Wood and Stone to build your first defense.',
                objectives: [
                    { type: 'collect', item: 'wood', amount: 5, current: 0, done: false },
                    { type: 'collect', item: 'stone', amount: 3, current: 0, done: false }
                ],
                reward: { gold: 10, xp: 50 },
                nextQuest: 'q2_farm',
                giver: 'villager'
            },
            'q2_farm': {
                id: 'q2_farm',
                title: 'The Farmer',
                description: 'Plant some seeds to grow food. You will need it.',
                objectives: [
                    { type: 'action', action: 'plant', amount: 3, current: 0, done: false }
                ],
                reward: { gold: 20, item: 'wood', amount: 10 },
                nextQuest: 'q3_defense',
                giver: 'villager'
            },
            'q3_defense': {
                id: 'q3_defense',
                title: 'Fortification',
                description: 'Build a Fence to keep zombies out.',
                objectives: [
                    { type: 'action', action: 'build_fence', amount: 2, current: 0, done: false }
                ],
                reward: { gold: 50, item: 'sword', amount: 1 },
                nextQuest: 'q4_slayer',
                giver: 'merchant'
            },
            'q4_slayer': {
                id: 'q4_slayer',
                title: 'Zombie Slayer',
                description: 'Kill 3 Zombies using your new sword.',
                objectives: [
                    { type: 'kill', target: 'zombie', amount: 3, current: 0, done: false }
                ],
                reward: { gold: 100, item: 'gold', amount: 50 },
                nextQuest: null,
                giver: 'villager'
            }
        };

        this.activeQuest = null;
        this.completedQuests = [];
    }

    getAvailableQuest(npcType) {
        const chain = ['q1_start', 'q2_farm', 'q3_defense', 'q4_slayer'];
        let targetId = null;
        for (const id of chain) {
            if (!this.completedQuests.includes(id)) {
                targetId = id;
                break;
            }
        }

        if (!targetId) return null;
        if (this.activeQuest && this.activeQuest.id === targetId) return null;

        const q = this.questDB[targetId];
        if (q.giver === npcType) return q;

        return null;
    }

    startQuest(id) {
        if (this.completedQuests.includes(id)) return;

        const template = this.questDB[id];
        if (!template) return;

        this.activeQuest = JSON.parse(JSON.stringify(template));
        console.log(`📜 Quest Started: ${this.activeQuest.title}`);

        this.updateUI();

        // Notification
        this.scene.events.emit('show-floating-text', {
            x: this.scene.player.x,
            y: this.scene.player.y - 50,
            text: "Quest Accepted!",
            color: '#FFFF00'
        });
    }

    update(delta) {
        if (!this.activeQuest) return;

        let changed = false;
        let allDone = true;

        if (this.scene.inventorySystem) {
            const inv = this.scene.inventorySystem;

            for (const obj of this.activeQuest.objectives) {
                if (obj.done) continue;

                if (obj.type === 'collect') {
                    const count = inv.getItemCount(obj.item);
                    if (count !== obj.current) {
                        obj.current = count;
                        changed = true;
                    }
                    if (obj.current >= obj.amount) {
                        obj.done = true;
                        this.scene.events.emit('show-floating-text', { x: this.scene.player.x, y: this.scene.player.y, text: "Objective Complete!" });
                    }
                }
            }
        }

        for (const obj of this.activeQuest.objectives) {
            if (!obj.done) allDone = false;
        }

        if (changed) this.updateUI();

        if (allDone) {
            this.completeQuest();
        }
    }

    trackAction(actionType, amount = 1) {
        if (!this.activeQuest) return;

        let changed = false;
        for (const obj of this.activeQuest.objectives) {
            if (obj.done) continue;

            if (obj.type === 'action' && obj.action === actionType) {
                obj.current += amount;
                changed = true;
                if (obj.current >= obj.amount) {
                    obj.done = true;
                    changed = true;
                }
            }
            if (obj.type === 'kill' && obj.target === actionType) {
                obj.current += amount;
                changed = true;
                if (obj.current >= obj.amount) {
                    obj.done = true;
                    changed = true;
                }
            }
        }
        if (changed) this.updateUI();
    }

    completeQuest() {
        console.log(`🏆 Quest Complete: ${this.activeQuest.title}`);

        if (this.activeQuest.reward) {
            const r = this.activeQuest.reward;
            if (r.gold && this.scene.inventorySystem) {
                this.scene.inventorySystem.addGold(r.gold);
            }
            if (r.item && this.scene.inventorySystem) {
                this.scene.inventorySystem.addItem(r.item, r.amount || 1);
            }
        }

        this.scene.events.emit('show-floating-text', {
            x: this.scene.player.x,
            y: this.scene.player.y - 50,
            text: "Quest Complete!",
            color: '#00FF00'
        });

        this.completedQuests.push(this.activeQuest.id);
        const next = this.activeQuest.nextQuest;
        this.activeQuest = null;
        this.updateUI();

        if (next) {
            console.log('Next quest available at NPC.');
        }
    }

    updateUI() {
        const ui = this.scene.scene.get('UIScene');
        if (ui && ui.updateQuestTracker) {
            ui.updateQuestTracker(this.activeQuest);
        }
    }
}