/**
 * Export themes. A theme is a self-contained CSS stylesheet plus the font and
 * colour tokens exporters use to set defaults (EPUB reading-mode overrides,
 * DOCX/ODT font families, PDF margins).
 *
 * Four themes ship by default:
 *   - Ink        — neutral serif, light (the default trade trim size look)
 *   - Parchment  — warm cream paper, dark text
 *   - Nocturne   — dark mode, light text
 *   - Terminal   — monospace, terminal aesthetic
 */

export interface ThemeColors {
  text: string;
  background: string;
  accent: string;
  muted: string;
  heading: string;
}

export interface Theme {
  id: string;
  name: string;
  /** Body font family. */
  fontFamily: string;
  /** Heading font family (falls back to fontFamily when null). */
  headingFont: string | null;
  /** Base body font size (CSS length). */
  fontSize: string;
  /** Body line height. */
  lineHeight: string;
  /** Paragraph indent. */
  paragraphIndent: string;
  colors: ThemeColors;
  /** Full stylesheet, scoped under `.ps-doc`, ready to inline in HTML/EPUB. */
  css: string;
}

const baseRules = (t: Theme): string => `
  .ps-doc {
    font-family: ${t.fontFamily};
    font-size: ${t.fontSize};
    line-height: ${t.lineHeight};
    color: ${t.colors.text};
    background: ${t.colors.background};
  }
  .ps-doc h1, .ps-doc h2, .ps-doc h3 {
    font-family: ${t.headingFont ?? t.fontFamily};
    color: ${t.colors.heading};
    line-height: 1.25;
    margin: 1.4em 0 0.6em;
  }
  .ps-doc h1 { font-size: 2em; }
  .ps-doc h2 { font-size: 1.5em; }
  .ps-doc h3 { font-size: 1.2em; }
  .ps-doc p {
    margin: 0;
    text-indent: ${t.paragraphIndent};
    orphans: 2;
    widows: 2;
  }
  .ps-doc p:first-of-type { text-indent: none; }
  .ps-doc blockquote {
    margin: 1em 0;
    padding: 0.2em 1em;
    border-left: 3px solid ${t.colors.accent};
    color: ${t.colors.muted};
    font-style: italic;
  }
  .ps-doc pre {
    white-space: pre-wrap;
    word-wrap: break-word;
    background: ${t.colors.background};
    border: 1px solid ${t.colors.muted};
    border-radius: 4px;
    padding: 0.6em 0.8em;
    font-size: 0.9em;
  }
  .ps-doc a { color: ${t.colors.accent}; text-decoration: underline; }
  .ps-doc .scene-break {
    text-align: center;
    margin: 1.4em 0;
    color: ${t.colors.muted};
  }
`;

const makeTheme = (spec: Omit<Theme, "css">): Theme => ({
  ...spec,
  css: baseRules(spec as Theme),
});

const ink: Theme = makeTheme({
  id: "ink",
  name: "Ink",
  fontFamily: '"Iowan Old Style", "Palatino Linotype", Palatino, Georgia, serif',
  headingFont: '"Iowan Old Style", "Palatino Linotype", Palatino, Georgia, serif',
  fontSize: "11pt",
  lineHeight: "1.55",
  paragraphIndent: "1.4em",
  colors: {
    text: "#1a1a1a",
    background: "#ffffff",
    accent: "#7a2e2e",
    muted: "#6b6b6b",
    heading: "#101010",
  },
});

const parchment: Theme = makeTheme({
  id: "parchment",
  name: "Parchment",
  fontFamily: '"Iowan Old Style", "Palatino Linotype", Palatino, Georgia, serif',
  headingFont: '"Garamond", "EB Garamond", Georgia, serif',
  fontSize: "11pt",
  lineHeight: "1.6",
  paragraphIndent: "1.4em",
  colors: {
    text: "#3a3226",
    background: "#f4ecd8",
    accent: "#8a5a2b",
    muted: "#7a6f5c",
    heading: "#4a3a22",
  },
});

const nocturne: Theme = makeTheme({
  id: "nocturne",
  name: "Nocturne",
  fontFamily: '"Iowan Old Style", "Palatino Linotype", Palatino, Georgia, serif',
  headingFont: '"Iowan Old Style", "Palatino Linotype", Palatino, Georgia, serif',
  fontSize: "11pt",
  lineHeight: "1.6",
  paragraphIndent: "1.4em",
  colors: {
    text: "#d8d8d8",
    background: "#14161a",
    accent: "#7fb3ff",
    muted: "#9aa0aa",
    heading: "#ffffff",
  },
});

const terminal: Theme = makeTheme({
  id: "terminal",
  name: "Terminal",
  fontFamily: '"JetBrains Mono", "Fira Code", "SF Mono", Menlo, Consolas, monospace',
  headingFont: '"JetBrains Mono", "Fira Code", "SF Mono", Menlo, Consolas, monospace',
  fontSize: "9.5pt",
  lineHeight: "1.5",
  paragraphIndent: "0",
  colors: {
    text: "#d6ffdb",
    background: "#0b0f10",
    accent: "#7dff9c",
    muted: "#7fae86",
    heading: "#b6ffbf",
  },
});

/** All available themes, keyed by id. */
export const THEMES: Record<string, Theme> = {
  ink,
  parchment,
  nocturne,
  terminal,
};

/** The default theme id. */
export const DEFAULT_THEME_ID = "ink";

/** Look up a theme by id, falling back to the default. */
export function getTheme(id?: string): Theme {
  return THEMES[id ?? DEFAULT_THEME_ID] ?? ink;
}