import type { ThemeConfig, SettingsYaml } from './schema';

/** The preset used when none is configured. */
export const DEFAULT_PRESET = 'studio-modern';

export const THEME_PRESETS: Record<string, ThemeConfig> = {
  'studio-modern': {
    preset: 'studio-modern',
    accent: '#e60012',
    fonts: { heading: 'Archivo', body: 'Archivo', caption: 'IBM Plex Mono' },
    radius: 0,
    photoFrame: 'none',
    grain: false,
    headerDot: true,
    heroStyle: 'split',
  },
  studio: {
    preset: 'studio',
    accent: '#e60012',
    fonts: { heading: 'Playfair Display', body: 'DM Sans', caption: 'EB Garamond' },
    radius: 0,
    photoFrame: 'passepartout',
    grain: true,
    headerDot: true,
    heroStyle: 'split',
  },
  minimal: {
    preset: 'minimal',
    accent: '#000000',
    fonts: { heading: 'Geist', body: 'Geist', caption: 'IBM Plex Mono' },
    radius: 0,
    photoFrame: 'none',
    grain: false,
    headerDot: false,
    heroStyle: 'fullbleed',
  },
  editorial: {
    preset: 'editorial',
    accent: '#8B2500',
    fonts: { heading: 'Bodoni Moda', body: 'Newsreader', caption: 'Spectral' },
    radius: 0,
    photoFrame: 'shadow',
    grain: false,
    headerDot: false,
    heroStyle: 'split',
  },
  classic: {
    preset: 'classic',
    accent: '#c49a3c',
    fonts: { heading: 'Cinzel', body: 'Crimson Pro', caption: 'Crimson Pro' },
    radius: 12,
    photoFrame: 'passepartout',
    grain: false,
    headerDot: true,
    heroStyle: 'minimal',
  },
  noir: {
    preset: 'noir',
    accent: '#ff6b35',
    fonts: { heading: 'Libre Baskerville', body: 'Source Sans 3', caption: 'Space Mono' },
    radius: 0,
    photoFrame: 'passepartout',
    grain: true,
    headerDot: false,
    heroStyle: 'fullbleed',
  },
  monograph: {
    preset: 'monograph',
    accent: '#333333',
    fonts: { heading: 'Instrument Serif', body: 'Inter', caption: 'IBM Plex Mono' },
    radius: 0,
    photoFrame: 'none',
    grain: false,
    headerDot: false,
    heroStyle: 'typographic',
  },
};

export const VALID_PHOTO_FRAMES = ['none', 'passepartout', 'shadow'];
export const VALID_HERO_STYLES = [
  'split',
  'fullbleed',
  'minimal',
  'stacked',
  'typographic',
  'mosaic',
  'cover', // EXPERIMENTAL: fullscreen splash with a single "Enter" link
];
export const VALID_LAYOUTS = [
  'masonry',
  'uniform',
  'showcase',
  'filmstrip',
  'editorial-flow',
  'essay',
  'justified', // EXPERIMENTAL: row-based layout with equal heights
];

/**
 * Corner radius reaches CSS as `${radius}px` (app/layout.tsx: `--radius-sm`)
 * and `${radius * 1.5}px` (`--radius-md`), so a value that is not actually a
 * number — `radius: "8px"` in hand-edited YAML, say — does not fail loudly,
 * it becomes `8pxpx` and `NaNpx` (#633). photoFrame and heroStyle, on either
 * side of this field, are already checked against an allowlist; this is the
 * same treatment for the one numeric scalar in ThemeConfig.
 */
const THEME_RADIUS_MAX = 64; // Presets top out at 16; generous but not unbounded.
function resolveRadius(raw: unknown, fallback: number): number {
  if (typeof raw !== 'number' || !Number.isFinite(raw)) return fallback;
  return Math.min(THEME_RADIUS_MAX, Math.max(0, raw));
}

/** `--accent` and `--accent-dim` (app/layout.tsx) take this verbatim. */
function resolveAccent(raw: unknown, fallback: string): string {
  return typeof raw === 'string' && raw.trim() ? raw : fallback;
}

/** `String(theme.grain)`/`String(theme.headerDot)` become a `data-*` attribute
 * either way, but a non-boolean is a sign the value was never meant for this
 * field at all — a typo'd key one level up, say — so it falls back rather
 * than being coerced into something that reads as intentional. */
function resolveThemeBoolean(raw: unknown, fallback: boolean): boolean {
  return typeof raw === 'boolean' ? raw : fallback;
}

export function resolveTheme(raw?: SettingsYaml['theme']): ThemeConfig {
  if (!raw) return { ...THEME_PRESETS[DEFAULT_PRESET] };

  if (typeof raw === 'string') {
    const preset = THEME_PRESETS[raw];
    if (!preset) {
      throw new Error(
        `Unknown theme preset "${raw}". Valid presets: ${Object.keys(THEME_PRESETS).join(', ')}`,
      );
    }
    return { ...preset };
  }

  const baseName = raw.preset ?? DEFAULT_PRESET;
  const base = THEME_PRESETS[baseName];
  if (!base) {
    throw new Error(
      `Unknown theme preset "${baseName}". Valid presets: ${Object.keys(THEME_PRESETS).join(', ')}`,
    );
  }

  return {
    preset: baseName,
    accent: resolveAccent(raw.accent, base.accent),
    fonts: {
      heading: raw.fonts?.heading ?? base.fonts.heading,
      body: raw.fonts?.body ?? base.fonts.body,
      caption: raw.fonts?.caption ?? base.fonts.caption,
    },
    radius: resolveRadius(raw.radius, base.radius),
    photoFrame: VALID_PHOTO_FRAMES.includes(raw.photoFrame ?? '')
      ? (raw.photoFrame as ThemeConfig['photoFrame'])
      : base.photoFrame,
    grain: resolveThemeBoolean(raw.grain, base.grain),
    headerDot: resolveThemeBoolean(raw.headerDot, base.headerDot),
    heroStyle: VALID_HERO_STYLES.includes(raw.heroStyle ?? '')
      ? (raw.heroStyle as ThemeConfig['heroStyle'])
      : base.heroStyle,
  };
}

export function getGoogleFontsUrl(theme: ThemeConfig): string {
  const weights = '300;400;500;600';
  const families = [...new Set([theme.fonts.heading, theme.fonts.body, theme.fonts.caption])];
  const params = families.map((f) => `family=${f.replace(/ /g, '+')}:wght@${weights}`).join('&');
  return `https://fonts.googleapis.com/css2?${params}&display=swap`;
}