tethys.backend/app/Controllers/Http/Api/AvatarController.ts

import type { HttpContext } from '@adonisjs/core/http';
import { StatusCodes } from 'http-status-codes';
import redis from '@adonisjs/redis/services/main';

const PREFIXES = ['von', 'van', 'de', 'del', 'della', 'di', 'da', 'dos', 'du', 'le', 'la'];
const DEFAULT_SIZE = 50;
const MIN_SIZE = 16;
const MAX_SIZE = 512;
const FONT_SIZE_RATIO = 0.4;
const COLOR_LIGHTENING_PERCENT = 60;
const COLOR_DARKENING_FACTOR = 0.6;
const CACHE_TTL = 24 * 60 * 60; // 24 hours instead of 1 hour

export default class AvatarController {
    public async generateAvatar({ request, response }: HttpContext) {
        try {
            const { name, size = DEFAULT_SIZE } = request.only(['name', 'size']);

            // Enhanced validation
            if (!name || typeof name !== 'string' || name.trim().length === 0) {
                return response.status(StatusCodes.BAD_REQUEST).json({
                    error: 'Name is required and must be a non-empty string',
                });
            }

            const parsedSize = this.validateSize(size);
            if (!parsedSize.isValid) {
                return response.status(StatusCodes.BAD_REQUEST).json({
                    error: parsedSize.error,
                });
            }

            // Build a unique cache key for the given name and size
            const cacheKey = `avatar:${this.sanitizeName(name)}-${parsedSize.value}`;
            // const cacheKey = `avatar:${name.trim().toLowerCase()}-${size}`;
            try {
                const cachedSvg = await redis.get(cacheKey);
                if (cachedSvg) {
                    this.setResponseHeaders(response);
                    return response.send(cachedSvg);
                }
            } catch (redisError) {
                // Log redis error but continue without cache
                console.warn('Redis cache read failed:', redisError);
            }

            const initials = this.getInitials(name);
            const colors = this.generateColors(name);
            const svgContent = this.createSvg(size, colors, initials);

            // // Cache the generated avatar for future use, e.g. 1 hour expiry
            try {
                await redis.setex(cacheKey, CACHE_TTL, svgContent);
            } catch (redisError) {
                // Log but don't fail the request
                console.warn('Redis cache write failed:', redisError);
            }

            this.setResponseHeaders(response);
            return response.send(svgContent);
        } catch (error) {
            console.error('Avatar generation error:', error);
            return response.status(StatusCodes.INTERNAL_SERVER_ERROR).json({
                error: 'Failed to generate avatar',
            });
        }
    }

    private validateSize(size: any): { isValid: boolean; value?: number; error?: string } {
        const numSize = Number(size);

        if (isNaN(numSize)) {
            return { isValid: false, error: 'Size must be a valid number' };
        }

        if (numSize < MIN_SIZE || numSize > MAX_SIZE) {
            return {
                isValid: false,
                error: `Size must be between ${MIN_SIZE} and ${MAX_SIZE}`,
            };
        }

        return { isValid: true, value: Math.floor(numSize) };
    }

    private sanitizeName(name: string): string {
        return name
            .trim()
            .toLowerCase()
            .replace(/[^a-z0-9\s-]/gi, '');
    }

    private getInitials(name: string): string {
        const sanitized = name.trim().replace(/\s+/g, ' '); // normalize whitespace
        const parts = sanitized
            .split(' ')
            .filter((part) => part.length > 0)
            .map((part) => part.trim());

        if (parts.length === 0) {
            return 'NA';
        }

        if (parts.length === 1) {
            // For single word, take first 2 characters or first char if only 1 char
            return parts[0].substring(0, Math.min(2, parts[0].length)).toUpperCase();
        }

        return this.getMultiWordInitials(parts);
    }

    private getMultiWordInitials(parts: string[]): string {
        // Filter out prefixes and short words
        const significantParts = parts.filter((part) => !PREFIXES.includes(part.toLowerCase()) && part.length > 1);

        if (significantParts.length === 0) {
            // Fallback to first and last regardless of prefixes
            const firstName = parts[0];
            const lastName = parts[parts.length - 1];
            return (firstName.charAt(0) + lastName.charAt(0)).toUpperCase();
        }

        if (significantParts.length === 1) {
            return significantParts[0].substring(0, 2).toUpperCase();
        }

        // Take first and last significant parts
        const firstName = significantParts[0];
        const lastName = significantParts[significantParts.length - 1];
        return (firstName.charAt(0) + lastName.charAt(0)).toUpperCase();
    }

    private generateColors(name: string): { background: string; text: string } {
        const baseColor = this.getColorFromName(name);
        return {
            background: this.lightenColor(baseColor, COLOR_LIGHTENING_PERCENT),
            text: this.darkenColor(baseColor),
        };
    }

    private createSvg(size: number, colors: { background: string; text: string }, initials: string): string {
        const fontSize = Math.max(12, Math.floor(size * FONT_SIZE_RATIO)); // Ensure readable font size

        // Escape any potential HTML/XML characters in initials
        const escapedInitials = this.escapeXml(initials);

        return `<svg width="${size}" height="${size}" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 ${size} ${size}">
                    <rect width="100%" height="100%" fill="#${colors.background}" rx="${size * 0.1}"/>
                    <text x="50%" y="50%" dominant-baseline="central" text-anchor="middle" 
                            font-weight="600" font-family="-apple-system, BlinkMacSystemFont, 'Segoe UI', system-ui, sans-serif" 
                            font-size="${fontSize}" fill="#${colors.text}">${escapedInitials}</text>
                </svg>`;
    }

    private escapeXml(text: string): string {
        return text.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;').replace(/"/g, '&quot;').replace(/'/g, '&apos;');
    }

    private setResponseHeaders(response: HttpContext['response']): void {
        response.header('Content-Type', 'image/svg+xml');
        response.header('Cache-Control', 'public, max-age=86400'); // Cache for 1 day
        response.header('ETag', `"${Date.now()}"`); // Simple ETag
    }

    private getColorFromName(name: string): string {
        let hash = 0;
        const normalizedName = name.toLowerCase().trim();

        for (let i = 0; i < normalizedName.length; i++) {
            hash = normalizedName.charCodeAt(i) + ((hash << 5) - hash);
            hash = hash & hash; // Convert to 32-bit integer
        }

        // Ensure we get vibrant colors by constraining the color space
        const colorParts = [];
        for (let i = 0; i < 3; i++) {
            let value = (hash >> (i * 8)) & 0xff;
            // Ensure minimum color intensity for better contrast
            value = Math.max(50, value);
            colorParts.push(value.toString(16).padStart(2, '0'));
        }
        return colorParts.join('');
    }

    private lightenColor(hexColor: string, percent: number): string {
        const r = parseInt(hexColor.substring(0, 2), 16);
        const g = parseInt(hexColor.substring(2, 4), 16);
        const b = parseInt(hexColor.substring(4, 6), 16);

        const lightenValue = (value: number) => Math.min(255, Math.floor(value + (255 - value) * (percent / 100)));

        const newR = lightenValue(r);
        const newG = lightenValue(g);
        const newB = lightenValue(b);

        return ((newR << 16) | (newG << 8) | newB).toString(16).padStart(6, '0');
    }

    private darkenColor(hexColor: string): string {
        const r = parseInt(hexColor.slice(0, 2), 16);
        const g = parseInt(hexColor.slice(2, 4), 16);
        const b = parseInt(hexColor.slice(4, 6), 16);

        const darkenValue = (value: number) => Math.max(0, Math.floor(value * COLOR_DARKENING_FACTOR));

        const darkerR = darkenValue(r);
        const darkerG = darkenValue(g);
        const darkerB = darkenValue(b);

        return ((darkerR << 16) + (darkerG << 8) + darkerB).toString(16).padStart(6, '0');
    }
}