import type { SubtitleSegment } from "../asr/types.js";

/**
 * Options for customising the ASS [V4+ Styles] section.
 * Every field is optional — omitted values fall back to the built-in defaults.
 *
 * Colour strings use the ASS `&HAABBGGRR` hex format, e.g. `&H00FFFFFF` for white.
 */
export interface AssStyleOptions {
  /** Font name (default: `"Arial"`). */
  fontName?: string;
  /** Font size in points (default: `14`). */
  fontSize?: number;
  /** Primary (fill) colour in `&HAABBGGRR` format (default: `&H00FFFFFF` — white). */
  primaryColour?: string;
  /** Secondary colour / karaoke fill (default: `&H000000FF` — red). */
  secondaryColour?: string;
  /** Outline colour (default: `&H00000000` — black). */
  outlineColour?: string;
  /** Back/shadow colour (default: `&H80000000` — semi-transparent black). */
  backColour?: string;
  /** Bold: `-1` = true, `0` = false (default: `-1`). */
  bold?: number;
  /** Italic: `-1` = true, `0` = false (default: `0`). */
  italic?: number;
  /** Underline: `-1` = true, `0` = false (default: `0`). */
  underline?: number;
  /** StrikeOut: `-1` = true, `0` = false (default: `0`). */
  strikeOut?: number;
  /** Horizontal scale % (default: `100`). */
  scaleX?: number;
  /** Vertical scale % (default: `100`). */
  scaleY?: number;
  /** Letter spacing in pixels (default: `0`). */
  spacing?: number;
  /** Rotation angle in degrees (default: `0`). */
  angle?: number;
  /** Border style: `1` = outline + drop shadow, `3` = opaque box (default: `1`). */
  borderStyle?: number;
  /** Outline width in pixels (default: `2`). */
  outline?: number;
  /** Shadow depth in pixels (default: `2`). */
  shadow?: number;
  /**
   * Alignment: 1=bottom-left … 3=bottom-right,
   * 4=mid-left … 6=mid-right, 7=top-left … 9=top-right (default: `2` = bottom-centre).
   */
  alignment?: number;
  /** Left margin in pixels (default: `20`). */
  marginL?: number;
  /** Right margin in pixels (default: `20`). */
  marginR?: number;
  /** Vertical margin in pixels (default: `20`). */
  marginV?: number;
}

/** Built-in defaults applied when no style options are provided. */
const DEFAULT_STYLE: Required<AssStyleOptions> = {
  fontName: "Arial",
  fontSize: 14,
  primaryColour: "&H00FFFFFF",
  secondaryColour: "&H000000FF",
  outlineColour: "&H00000000",
  backColour: "&H80000000",
  bold: -1,
  italic: 0,
  underline: 0,
  strikeOut: 0,
  scaleX: 100,
  scaleY: 100,
  spacing: 0,
  angle: 0,
  borderStyle: 1,
  outline: 2,
  shadow: 2,
  alignment: 2,
  marginL: 20,
  marginR: 20,
  marginV: 20,
};

function msToAssTime(ms: number): string {
  const h = Math.floor(ms / 3_600_000);
  const m = Math.floor((ms % 3_600_000) / 60_000);
  const s = Math.floor((ms % 60_000) / 1_000);
  const cs = Math.floor((ms % 1_000) / 10);
  return [
    String(h),
    String(m).padStart(2, "0"),
    String(s).padStart(2, "0"),
  ].join(":") +
    "." +
    String(cs).padStart(2, "0");
}

/** Build the `[V4+ Styles]` section from partial options merged with defaults. */
function buildStyleSection(opts?: AssStyleOptions): string {
  const s = { ...DEFAULT_STYLE, ...opts };
  const formatLine = [
    "Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour,",
    "OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut,",
    "ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow,",
    "Alignment, MarginL, MarginR, MarginV, Encoding",
  ].join("");

  const styleLine = [
    "Style: Default,",
    s.fontName,
    ",",
    s.fontSize,
    ",",
    s.primaryColour,
    ",",
    s.secondaryColour,
    ",",
    s.outlineColour,
    ",",
    s.backColour,
    ",",
    s.bold,
    ",",
    s.italic,
    ",",
    s.underline,
    ",",
    s.strikeOut,
    ",",
    s.scaleX,
    ",",
    s.scaleY,
    ",",
    s.spacing,
    ",",
    s.angle,
    ",",
    s.borderStyle,
    ",",
    s.outline,
    ",",
    s.shadow,
    ",",
    s.alignment,
    ",",
    s.marginL,
    ",",
    s.marginR,
    ",",
    s.marginV,
    ",",
    "1",
  ].join("");

  return ["[V4+ Styles]", formatLine, styleLine].join("\n");
}

/**
 * Convert segments to ASS (Advanced SubStation Alpha) format.
 *
 * By default a built-in style is used (Arial/14pt white-on-black).
 * Pass {@link AssStyleOptions} to customise font, colours, layout, etc.
 */
export function toAss(
  segments: SubtitleSegment[],
  assStyle?: AssStyleOptions,
): string {
  const header = [
    "[Script Info]",
    "Title: Generated by jianying-subtitle",
    "ScriptType: v4.00+",
    "WrapStyle: 0",
    "ScaledBorderAndShadow: yes",
    "YCbCr Matrix: None",
    "",
    buildStyleSection(assStyle),
    "",
    "[Events]",
    [
      "Format: Layer, Start, End, Style, Name, MarginL,",
      "MarginR, MarginV, Effect, Text",
    ].join(""),
  ].join("\n");

  const events = segments
    .map((seg) => {
      return [
        "Dialogue: 0,",
        msToAssTime(seg.startMs),
        ",",
        msToAssTime(seg.endMs),
        ",Default,,0,0,0,,",
        seg.text,
      ].join("");
    })
    .join("\n");

  return header + "\n" + events + "\n";
}