/** The languages the key bar knows. Anything else gets the general set. */
export type Language = "html" | "css" | "javascript" | "json" | "markdown" | "shell" | "text";

/** A key that types something: a symbol, a pair with the caret inside, or a short snippet. */
export interface TypingKey {
  readonly label: string;
  /** The accessible name, when the label alone doesn't say it (pairs, snippets). */
  readonly name?: string;
  readonly text: string;
  /** Where the caret lands inside `text`; default after it. */
  readonly caret?: number;
}

const EXTENSIONS: Record<string, Language> = {
  html: "html",
  htm: "html",
  svg: "html",
  xml: "html",
  vue: "html",
  svelte: "html",
  astro: "html",
  css: "css",
  scss: "css",
  less: "css",
  js: "javascript",
  mjs: "javascript",
  cjs: "javascript",
  jsx: "javascript",
  ts: "javascript",
  mts: "javascript",
  cts: "javascript",
  tsx: "javascript",
  json: "json",
  jsonc: "json",
  webmanifest: "json",
  md: "markdown",
  markdown: "markdown",
  mdx: "markdown",
  sh: "shell",
  bash: "shell",
  zsh: "shell",
};

/** The language of a file, from its extension. */
export function languageOf(path: string): Language {
  const name = path.slice(path.lastIndexOf("/") + 1);
  const dot = name.lastIndexOf(".");
  return (dot > 0 && EXTENSIONS[name.slice(dot + 1).toLowerCase()]) || "text";
}

export const LANGUAGE_NAMES: Record<Language, string> = {
  html: "HTML",
  css: "CSS",
  javascript: "JavaScript",
  json: "JSON",
  markdown: "Markdown",
  shell: "Shell",
  text: "Coding",
};

const pair = (open: string, close: string, name: string): TypingKey => ({ label: `${open} ${close}`, name, text: open + close, caret: open.length });
const chars = (list: string): TypingKey[] => [...list].map((char) => ({ label: char, text: char }));

/**
 * The typing keys for each language, most reached-for first, since the row scrolls and the start
 * is what a thumb finds. These are the keys a phone keyboard buries behind its symbol pages.
 */
const KEYS: Record<Language, readonly TypingKey[]> = {
  html: [
    pair("<", ">", "Angle brackets"),
    ...chars("/="),
    pair('"', '"', "Double quotes"),
    { label: "<!--", name: "Comment", text: "<!--  -->", caret: 5 },
    ...chars("!-&;#.:'"),
    pair("{", "}", "Braces"),
    pair("(", ")", "Parentheses"),
  ],
  css: [
    pair("{", "}", "Braces"),
    ...chars(":;#.-"),
    pair("(", ")", "Parentheses"),
    ...chars("%!,>*~+@"),
    pair('"', '"', "Double quotes"),
    { label: "/*", name: "Comment", text: "/*  */", caret: 3 },
  ],
  javascript: [
    pair("(", ")", "Parentheses"),
    pair("{", "}", "Braces"),
    pair("[", "]", "Brackets"),
    { label: "=>", name: "Arrow", text: " => " },
    ...chars(";:=.,"),
    pair('"', '"', "Double quotes"),
    pair("'", "'", "Single quotes"),
    pair("`", "`", "Backticks"),
    ...chars("!?&|<>+-*/$_"),
    { label: "//", name: "Comment", text: "// " },
  ],
  json: [
    pair("{", "}", "Braces"),
    pair("[", "]", "Brackets"),
    pair('"', '"', "Double quotes"),
    ...chars(":,-."),
  ],
  markdown: [
    ...chars("#*_`"),
    pair("[", "]", "Brackets"),
    pair("(", ")", "Parentheses"),
    ...chars("->!|~"),
    { label: "```", name: "Code fence", text: "```\n\n```", caret: 4 },
  ],
  shell: [...chars("|>&;$~/-.*<"), pair('"', '"', "Double quotes"), pair("'", "'", "Single quotes"), ...chars("`=")],
  text: [
    pair("(", ")", "Parentheses"),
    pair("{", "}", "Braces"),
    pair("[", "]", "Brackets"),
    pair("<", ">", "Angle brackets"),
    ...chars("\"'`;:=/\\|&!?_-+*#$%"),
  ],
};

export function typingKeys(language: Language): readonly TypingKey[] {
  return KEYS[language];
}