import { CoverageTable } from '../tables';

/**
 * Get the index of the given glyph in the coverage table, or null if it is not
 * present in the table.
 *
 * @param table JSON representation of the coverage table
 * @param glyphId Index of the glyph to look for
 */
export default function getCoverageGlyphIndex(table: CoverageTable, glyphId: number): number | null {
  switch (table.format) {
    // https://docs.microsoft.com/en-us/typography/opentype/spec/chapter2#coverage-format-1
    case 1:
      const index = table.glyphs.indexOf(glyphId);
      return index !== -1
        ? index
        : null;
    // https://docs.microsoft.com/en-us/typography/opentype/spec/chapter2#coverage-format-2
    case 2:
      const range = table.ranges
        .find(range => range.start <= glyphId && range.end >= glyphId);
      return range
        ? range.index
        : null;
  }
}

export function listGlyphsByIndex(table: CoverageTable): { glyphId: number | [number, number], index: number }[] {
  switch (table.format) {
    case 1:
      return table.glyphs.map((glyphId, index) => ({ glyphId, index }));
    case 2:
      const results: { glyphId: number | [number, number], index: number }[] = [];
      for (const [index, range] of table.ranges.entries()) {
        if (range.end === range.start) {
          results.push({ glyphId: range.start, index });
        } else {
          results.push({ glyphId: [range.start, range.end + 1], index });
        }
      }
      return results;
  }
}