const { createCanvas, loadImage } = require('canvas');
const path = require('path');

/**
 * Calculates the XP required for the next level
 * @param {number} currentLevel - Current user level
 * @returns {number} XP required for next level
 */
function calculateNextLevelXP(currentLevel) {
    // Using the inverse of the level calculation formula from xpSystem.js
    // level = 0.47 * sqrt(xp)
    // Therefore, xp = (level/0.47)^2
    return Math.ceil(Math.pow((currentLevel + 1) / 0.47, 2));
}

/**
 * Generates a level card image for a user
 * @param {Object} user - User object containing id, username, xp, and level
 * @returns {Promise<Buffer>} - Returns a buffer containing the generated image
 */
async function generateLevelCard(user) {
    // Create canvas with dimensions matching the background image
    const canvas = createCanvas(1516, 662);
    const ctx = canvas.getContext('2d');

    try {
        // Load background image
        const background = await loadImage(path.join(__dirname, '../../assets/level_clean.png'));
        ctx.drawImage(background, 0, 0, canvas.width, canvas.height);

        // Load progress bar fill image
        const progressFill = await loadImage(path.join(__dirname, '../../assets/progress_fill.png'));

        // Calculate XP progress using the same formula as xpSystem.js
        const currentLevelXP = Math.floor(Math.pow(user.level / 0.47, 2));
        const nextLevelXP = Math.floor(calculateNextLevelXP(user.level));
        const xpInLevel = user.xp - currentLevelXP;
        const xpForLevel = nextLevelXP - currentLevelXP;
        // Clamp progress between 0 and 1
        const progress = Math.max(0, Math.min(1, xpInLevel / xpForLevel));
        // Clamp displayed XP to not exceed xpForLevel
        const displayXP = Math.min(Math.max(0, xpInLevel), xpForLevel);
        
        // Draw username
        ctx.font = 'bold 60px Arial';
        ctx.fillStyle = '#FFFFFF';
        ctx.textAlign = 'left';
        ctx.fillText(user.username, 420, 250);

        // Draw level
        ctx.font = 'bold 48px Arial';
        ctx.fillStyle = '#FFD700'; // Gold color for level
        ctx.fillText(`Level ${user.level}`, 420, 330);

        // Progress bar dimensions and position
        const progressBarX = 472;
        const progressBarY = 388;
        const progressBarWidth = 800;
        const progressBarHeight = 60;

        // Draw progress bar fill
        ctx.drawImage(
            progressFill,
            progressBarX,
            progressBarY,
            progressBarWidth * progress,
            progressBarHeight
        );

        // Draw XP progress text inside the bar, right-aligned
        ctx.font = 'bold 36px Arial';
        ctx.fillStyle = '#FFFFFF';
        ctx.textAlign = 'center';
        ctx.fillText(
            `${displayXP}/${xpForLevel} XP`,
            progressBarX + progressBarWidth / 2,
            progressBarY + progressBarHeight / 2 + 12 // adjust as needed
        );

        // Convert canvas to buffer
        return canvas.toBuffer('image/png');
    } catch (error) {
        console.error('Error generating level card:', error);
        throw error;
    }
}

module.exports = generateLevelCard;