import type { TenantThemeData } from '../../app.d.js';

/** Validates a theme background image URL is safe for CSS injection. */
function isSafeCssUrl(url: string): boolean {
	return /^\/api\/branding\/[0-9a-f-]+\/[a-z-]+$/.test(url);
}

/**
 * Client-side CSS variable mapping — mirrors server-side theme-css.ts
 */
const FIELD_MAP: Record<string, { cssVar: string; mode: 'light' | 'dark' }> = {};

const vars = [
	['PageBg', '--color-page-bg'],
	['NavBg', '--color-nav-bg'],
	['ColumnBg', '--color-column-bg'],
	['ColumnBorder', '--color-column-border'],
	['ColumnText', '--color-column-text'],
	['CardBg', '--color-card-bg'],
	['CardBorder', '--color-card-border'],
	['CardText', '--color-card-text'],
	['CardRadius', '--color-card-radius'],
	['Primary', '--color-primary'],
	['PrimaryHover', '--color-primary-hover'],
	['Danger', '--color-danger'],
	['DangerHover', '--color-danger-hover'],
	['Success', '--color-success'],
	['Warning', '--color-warning']
] as const;

for (const [suffix, cssVar] of vars) {
	FIELD_MAP[`light${suffix}`] = { cssVar, mode: 'light' };
	FIELD_MAP[`dark${suffix}`] = { cssVar, mode: 'dark' };
}

function hexToRgba(hex: string, opacity: number): string {
	const h = hex.replace('#', '');
	const r = parseInt(h.substring(0, 2), 16);
	const g = parseInt(h.substring(2, 4), 16);
	const b = parseInt(h.substring(4, 6), 16);
	return `rgba(${r}, ${g}, ${b}, ${opacity})`;
}

/**
 * Generates CSS from theme data and writes it into the <style id="tenant-theme"> element.
 * This mirrors what generateTenantCSS does server-side, but runs in the browser
 * so theme changes take effect immediately without a full page reload.
 */
export function persistThemeCSS(theme: TenantThemeData) {
	if (typeof document === 'undefined') return;
	const lightVars: string[] = [];
	const darkVars: string[] = [];

	for (const [field, { cssVar, mode }] of Object.entries(FIELD_MAP)) {
		const value = (theme as any)[field];
		if (value == null) continue;
		const target = mode === 'dark' ? darkVars : lightVars;
		target.push(`  ${cssVar}: ${value};`);
	}

	// Handle opacity for columns
	if (theme.lightColumnOpacity != null && theme.lightColumnBg?.startsWith('#')) {
		const idx = lightVars.findIndex((v) => v.includes('--color-column-bg:'));
		if (idx !== -1) lightVars[idx] = `  --color-column-bg: ${hexToRgba(theme.lightColumnBg, theme.lightColumnOpacity)};`;
		if (theme.lightColumnOpacity < 1) lightVars.push(`  --column-backdrop-blur: blur(8px);`);
	}
	if (theme.lightCardOpacity != null && theme.lightCardBg?.startsWith('#')) {
		const idx = lightVars.findIndex((v) => v.includes('--color-card-bg:'));
		if (idx !== -1) lightVars[idx] = `  --color-card-bg: ${hexToRgba(theme.lightCardBg, theme.lightCardOpacity)};`;
		if (theme.lightCardOpacity < 1) lightVars.push(`  --card-backdrop-blur: blur(8px);`);
	}
	if (theme.darkColumnOpacity != null && theme.darkColumnBg?.startsWith('#')) {
		const idx = darkVars.findIndex((v) => v.includes('--color-column-bg:'));
		if (idx !== -1) darkVars[idx] = `  --color-column-bg: ${hexToRgba(theme.darkColumnBg, theme.darkColumnOpacity)};`;
		if (theme.darkColumnOpacity < 1) darkVars.push(`  --column-backdrop-blur: blur(8px);`);
	}
	if (theme.darkCardOpacity != null && theme.darkCardBg?.startsWith('#')) {
		const idx = darkVars.findIndex((v) => v.includes('--color-card-bg:'));
		if (idx !== -1) darkVars[idx] = `  --color-card-bg: ${hexToRgba(theme.darkCardBg, theme.darkCardOpacity)};`;
		if (theme.darkCardOpacity < 1) darkVars.push(`  --card-backdrop-blur: blur(8px);`);
	}

	// Handle background images
	const extraRules: string[] = [];
	if (theme.lightPageBgImage && isSafeCssUrl(theme.lightPageBgImage)) {
		extraRules.push(`.layout-page-bg { background-image: url('${theme.lightPageBgImage}'); }`);
	}
	if (theme.lightNavBgImage && isSafeCssUrl(theme.lightNavBgImage)) {
		extraRules.push(`.layout-nav-bg { background-image: url('${theme.lightNavBgImage}'); }`);
	}
	if (theme.darkPageBgImage && isSafeCssUrl(theme.darkPageBgImage)) {
		extraRules.push(`html.dark .layout-page-bg { background-image: url('${theme.darkPageBgImage}'); }`);
	}
	if (theme.darkNavBgImage && isSafeCssUrl(theme.darkNavBgImage)) {
		extraRules.push(`html.dark .layout-nav-bg { background-image: url('${theme.darkNavBgImage}'); }`);
	}

	let css = '';
	if (lightVars.length > 0) {
		css += `:root {\n${lightVars.join('\n')}\n}\n`;
	}
	if (darkVars.length > 0) {
		css += `html.dark {\n${darkVars.join('\n')}\n}\n`;
	}
	if (extraRules.length > 0) {
		css += extraRules.join('\n') + '\n';
	}

	// Find or create the <style id="tenant-theme"> element
	let styleEl = document.getElementById('tenant-theme') as HTMLStyleElement | null;
	if (!styleEl) {
		styleEl = document.createElement('style');
		styleEl.id = 'tenant-theme';
		document.head.appendChild(styleEl);
	}
	styleEl.textContent = css;
}