class BuildSystem {
    constructor(scene) {
        this.scene = scene;
        this.buildMode = false;
        this.selectedBuilding = 'fence';
        this.previewSprite = null;
        this.placedBuildings = [];

        // Building definitions
        this.buildings = {
            'fence': {
                name: 'Fence (Old)',
                textureKey: 'fence_isometric',
                cost: { wood: 2 },
                collision: false,
                scale: 0.3
            },
            'fence_post': {
                name: 'Fence Post',
                textureKey: 'fence_post',
                cost: { wood: 1 },
                collision: false,
                scale: 0.2
            },
            'fence_horizontal': {
                name: 'Fence →',
                textureKey: 'fence_horizontal',
                cost: { wood: 2 },
                collision: false,
                scale: 0.2
            },
            'fence_vertical': {
                name: 'Fence ↓',
                textureKey: 'fence_vertical',
                cost: { wood: 2 },
                collision: false,
                scale: 0.2
            },
            'fence_corner': {
                name: 'Fence ⌞',
                textureKey: 'fence_corner',
                cost: { wood: 2 },
                collision: false,
                scale: 0.2
            },
            'barn': {
                name: 'Barn',
                textureKey: 'barn_isometric',
                cost: { wood: 40, stone: 20 },
                collision: true,
                scale: 0.5
            },
            'grave': {
                name: 'Grave',
                textureKey: 'grave_zombie',
                cost: { stone: 10 },
                collision: false,
                scale: 0.3
            },
            'farmhouse': {
                name: 'Farmhouse',
                textureKey: 'farmhouse_isometric',
                cost: { wood: 50, stone: 30, gold: 100 },
                collision: true,
                scale: 0.5
            },
            'blacksmith': {
                name: 'Blacksmith',
                textureKey: 'blacksmith_workshop',
                cost: { wood: 30, stone: 40, gold: 80 },
                collision: true,
                scale: 0.45
            }
        };
    }

    toggleBuildMode() {
        this.buildMode = !this.buildMode;
        console.log(`Build Mode: ${this.buildMode ? 'ON' : 'OFF'}`);

        // Show tutorial on first time
        if (this.buildMode && !this.tutorialShown) {
            this.showTutorial();
            this.tutorialShown = true;
        }

        // Notify UI
        const uiScene = this.scene.scene.get('UIScene');
        if (uiScene) {
            uiScene.toggleBuildMenu(this.buildMode);
        }

        // Show/hide preview
        if (this.buildMode) {
            this.createPreview();
        } else {
            this.destroyPreview();
        }

        return this.buildMode;
    }

    selectBuilding(buildingId) {
        if (!this.buildings[buildingId]) return;
        this.selectedBuilding = buildingId;

        // Update UI
        const uiScene = this.scene.scene.get('UIScene');
        if (uiScene) {
            uiScene.updateBuildSelection(this.buildings[buildingId].name);
        }

        // Refresh preview
        if (this.buildMode) {
            this.destroyPreview();
            this.createPreview();
        }
    }

    createPreview() {
        const building = this.buildings[this.selectedBuilding];
        if (!this.scene.textures.exists(building.textureKey)) {
            console.warn(`Texture not found: ${building.textureKey}`);
            return;
        }

        this.previewSprite = this.scene.add.sprite(0, 0, building.textureKey);
        this.previewSprite.setOrigin(0.5, 1);
        this.previewSprite.setAlpha(0.6);
        this.previewSprite.setDepth(10000); // Always on top
        this.previewSprite.setScale(building.scale || 1.0);
    }

    destroyPreview() {
        if (this.previewSprite) {
            this.previewSprite.destroy();
            this.previewSprite = null;
        }
    }

    update() {
        if (!this.buildMode || !this.previewSprite) return;

        // Follow mouse
        const pointer = this.scene.input.activePointer;
        const worldPoint = this.scene.cameras.main.getWorldPoint(pointer.x, pointer.y);
        const gridPos = this.scene.iso.toGrid(worldPoint.x, worldPoint.y);
        const screenPos = this.scene.iso.toScreen(gridPos.x, gridPos.y);

        this.previewSprite.setPosition(screenPos.x, screenPos.y);

        // Check if can place
        const canPlace = this.canPlaceAt(gridPos.x, gridPos.y);
        this.previewSprite.setTint(canPlace ? 0x00ff00 : 0xff0000);

        // Place on click
        if (pointer.isDown && canPlace) {
            this.placeBuilding(gridPos.x, gridPos.y);
        }
    }

    canPlaceAt(gridX, gridY) {
        // Check if already has building
        const exists = this.placedBuildings.find(b => b.gridX === gridX && b.gridY === gridY);
        if (exists) return false;

        // Check terrain (only on farm tiles)
        if (!this.scene.terrainSystem) return false;
        const tile = this.scene.terrainSystem.getTile(gridX, gridY);
        if (!tile || tile.type !== 'farm') return false;

        // Check cost
        const building = this.buildings[this.selectedBuilding];
        if (!this.hasResources(building.cost)) return false;

        return true;
    }

    hasResources(cost) {
        const inv = this.scene.inventorySystem;
        if (!inv) return false;

        for (const [resource, amount] of Object.entries(cost)) {
            if (resource === 'gold') {
                if (inv.gold < amount) return false;
            } else {
                if (!inv.hasItem(resource, amount)) return false;
            }
        }
        return true;
    }

    placeBuilding(gridX, gridY) {
        const building = this.buildings[this.selectedBuilding];

        // Consume resources
        const inv = this.scene.inventorySystem;
        for (const [resource, amount] of Object.entries(building.cost)) {
            if (resource === 'gold') {
                inv.gold -= amount;
            } else {
                inv.removeItem(resource, amount);
            }
        }

        // Create sprite
        const screenPos = this.scene.iso.toScreen(gridX, gridY);
        const sprite = this.scene.add.sprite(screenPos.x, screenPos.y, building.textureKey);
        sprite.setOrigin(0.5, 1);
        sprite.setScale(building.scale || 1.0);
        sprite.setDepth(this.scene.iso.getDepth(gridX, gridY) + 5); // Above terrain

        // Store
        this.placedBuildings.push({
            gridX,
            gridY,
            type: this.selectedBuilding,
            sprite,
            collision: building.collision
        });

        console.log(`🏗️ Placed ${building.name} at (${gridX}, ${gridY})`);

        // Update UI
        this.scene.events.emit('update-inventory');
    }

    isCollisionAt(gridX, gridY) {
        const building = this.placedBuildings.find(b => b.gridX === gridX && b.gridY === gridY);
        return building ? building.collision : false;
    }

    showTutorial() {
        const uiScene = this.scene.scene.get('UIScene');
        if (!uiScene) return;

        const width = this.scene.cameras.main.width;
        const height = this.scene.cameras.main.height;

        // Tutorial panel
        const panel = uiScene.add.container(width / 2, height / 2);
        panel.setDepth(10000);

        const bg = uiScene.add.rectangle(0, 0, 500, 300, 0x1a1a2e, 0.95);
        bg.setStrokeStyle(3, 0x00ff41);
        panel.add(bg);

        const title = uiScene.add.text(0, -120, '🏗️ BUILD MODE', {
            fontSize: '24px',
            fontFamily: 'Courier New',
            color: '#00ff41',
            fontStyle: 'bold'
        }).setOrigin(0.5);
        panel.add(title);

        const instructions = [
            'Controls:',
            '1-5: Select building type',
            'Mouse: Move preview',
            'Click: Place building',
            'B: Exit build mode',
            '',
            'Green = OK | Red = Blocked'
        ];

        const text = uiScene.add.text(0, 0, instructions.join('\n'), {
            fontSize: '16px',
            fontFamily: 'Courier New',
            color: '#ffffff',
            align: 'center',
            lineSpacing: 8
        }).setOrigin(0.5);
        panel.add(text);

        const closeBtn = uiScene.add.text(0, 120, '[Click to close]', {
            fontSize: '14px',
            color: '#888888'
        }).setOrigin(0.5);
        panel.add(closeBtn);

        // Auto-dismiss after 5 seconds
        uiScene.time.delayedCall(5000, () => {
            panel.destroy();
        });

        // Click to dismiss
        bg.setInteractive();
        bg.on('pointerdown', () => {
            panel.destroy();
        });
    }
}