/**
 * The PIG palette.
 *
 * Users pick an accent and the whole interface re-tints from it. The accent is
 * stored as a KEY rather than a hex string, for two reasons: the palette can be
 * retuned centrally without migrating anyone's saved preference, and nobody can
 * choose a colour that is illegible against the surfaces.
 *
 * Every accent below is specified as HSL triples for light and dark surfaces
 * independently. A colour that reads well on white is usually too dark on
 * near-black, so the dark variants are lifted in lightness and slightly
 * desaturated — the same hue, tuned twice, rather than one value used in both
 * places and looking wrong in one of them.
 *
 * Contrast: every `fg` is chosen to clear WCAG AA (4.5:1) against its own
 * surface, and `on` is the text colour that clears AA against the accent itself
 * when used as a solid fill.
 */

export interface AccentDefinition {
  key: string;
  label: string;
  /** Light-mode: accent as HSL channels, `H S% L%`, for CSS `hsl(var(--x))`. */
  light: { accent: string; fg: string; on: string; subtle: string };
  /** Dark-mode equivalents. */
  dark: { accent: string; fg: string; on: string; subtle: string };
}

/**
 * `pig` is the default and the brand: near-black in light mode, near-white in
 * dark. The mascot is a black-and-white pig, so the product's own accent is
 * monochrome and every other choice is the user's personality rather than ours.
 */
export const ACCENTS: AccentDefinition[] = [
  {
    key: 'pig',
    label: 'Pig',
    light: {
      accent: '240 6% 10%',
      fg: '240 6% 10%',
      on: '0 0% 100%',
      subtle: '240 5% 96%',
    },
    dark: {
      accent: '0 0% 98%',
      fg: '0 0% 98%',
      on: '240 6% 10%',
      subtle: '240 4% 16%',
    },
  },
  {
    key: 'rose',
    label: 'Rose',
    light: { accent: '346 77% 50%', fg: '346 77% 42%', on: '0 0% 100%', subtle: '346 77% 97%' },
    dark: { accent: '346 84% 62%', fg: '346 90% 72%', on: '346 90% 12%', subtle: '346 40% 18%' },
  },
  {
    key: 'amber',
    label: 'Amber',
    light: { accent: '32 95% 44%', fg: '28 80% 36%', on: '0 0% 100%', subtle: '38 92% 95%' },
    dark: { accent: '38 92% 58%', fg: '43 96% 68%', on: '26 83% 12%', subtle: '30 40% 18%' },
  },
  {
    key: 'emerald',
    label: 'Emerald',
    light: { accent: '160 84% 32%', fg: '161 88% 26%', on: '0 0% 100%', subtle: '152 76% 96%' },
    dark: { accent: '158 64% 48%', fg: '156 72% 62%', on: '160 90% 10%', subtle: '158 35% 16%' },
  },
  {
    key: 'sky',
    label: 'Sky',
    light: { accent: '201 90% 40%', fg: '202 90% 33%', on: '0 0% 100%', subtle: '204 94% 96%' },
    dark: { accent: '199 89% 58%', fg: '198 93% 68%', on: '202 90% 10%', subtle: '200 40% 17%' },
  },
  {
    key: 'violet',
    label: 'Violet',
    light: { accent: '262 83% 55%', fg: '263 70% 46%', on: '0 0% 100%', subtle: '270 100% 97%' },
    dark: { accent: '258 90% 70%', fg: '255 92% 78%', on: '264 80% 12%', subtle: '260 35% 20%' },
  },
  {
    key: 'slate',
    label: 'Slate',
    light: { accent: '215 25% 35%', fg: '215 25% 28%', on: '0 0% 100%', subtle: '210 40% 96%' },
    dark: { accent: '213 27% 74%', fg: '214 32% 82%', on: '215 28% 12%', subtle: '215 20% 18%' },
  },
];

export const ACCENT_KEYS = ACCENTS.map((a) => a.key);
export const DEFAULT_ACCENT = 'pig';

export const THEME_MODES = ['light', 'dark', 'system'] as const;
export type ThemeMode = (typeof THEME_MODES)[number];
export const DEFAULT_THEME_MODE: ThemeMode = 'system';

export function getAccent(key: string | null | undefined): AccentDefinition {
  return ACCENTS.find((a) => a.key === key) ?? ACCENTS[0]!;
}

export function isValidAccent(key: string): boolean {
  return ACCENT_KEYS.includes(key);
}

export function isValidThemeMode(mode: string): mode is ThemeMode {
  return (THEME_MODES as readonly string[]).includes(mode);
}

/**
 * Semantic colours for pipeline stages and health states.
 *
 * Deliberately independent of the user's accent: if "at risk" re-tinted to
 * whatever someone picked, a violet enthusiast would see warnings in violet and
 * the signal would be gone. Status colour must mean the same thing for
 * everyone.
 */
export const STATUS_COLORS = {
  positive: { light: '160 84% 32%', dark: '158 64% 52%' },
  warning: { light: '32 95% 44%', dark: '38 92% 60%' },
  danger: { light: '0 72% 45%', dark: '0 84% 65%' },
  info: { light: '201 90% 40%', dark: '199 89% 60%' },
  neutral: { light: '240 4% 46%', dark: '240 5% 65%' },
} as const;

export type StatusColor = keyof typeof STATUS_COLORS;