// @flow
/**
 * Predefined macros for KaTeX.
 * This can be used to define some commands in terms of others.
 */

import fontMetricsData from "./fontMetricsData";
import symbols from "./symbols";
import utils from "./utils";
import {Token} from "./Token";

/**
 * Provides context to macros defined by functions. Implemented by
 * MacroExpander.
 */
export interface MacroContextInterface {
    /**
     * Returns the topmost token on the stack, without expanding it.
     * Similar in behavior to TeX's `\futurelet`.
     */
    future(): Token;

    /**
     * Expand the next token only once (if possible), and return the resulting
     * top token on the stack (without removing anything from the stack).
     * Similar in behavior to TeX's `\expandafter\futurelet`.
     */
    expandAfterFuture(): Token;

    /**
     * Consume the specified number of arguments from the token stream,
     * and return the resulting array of arguments.
     */
    consumeArgs(numArgs: number): Token[][];
}

/** Macro tokens (in reverse order). */
export type MacroExpansion = {tokens: Token[], numArgs: number};

type MacroDefinition = string | MacroExpansion |
    (MacroContextInterface => (string | MacroExpansion));
export type MacroMap = {[string]: MacroDefinition};

const builtinMacros: MacroMap = {};
export default builtinMacros;

// This function might one day accept an additional argument and do more things.
export function defineMacro(name: string, body: MacroDefinition) {
    builtinMacros[name] = body;
}

//////////////////////////////////////////////////////////////////////
// macro tools

// LaTeX's \@firstoftwo{#1}{#2} expands to #1, skipping #2
// TeX source: \long\def\@firstoftwo#1#2{#1}
defineMacro("\\@firstoftwo", function(context) {
    const args = context.consumeArgs(2);
    return {tokens: args[0], numArgs: 0};
});

// LaTeX's \@secondoftwo{#1}{#2} expands to #2, skipping #1
// TeX source: \long\def\@secondoftwo#1#2{#2}
defineMacro("\\@secondoftwo", function(context) {
    const args = context.consumeArgs(2);
    return {tokens: args[1], numArgs: 0};
});

// LaTeX's \@ifnextchar{#1}{#2}{#3} looks ahead to the next (unexpanded)
// symbol.  If it matches #1, then the macro expands to #2; otherwise, #3.
// Note, however, that it does not consume the next symbol in either case.
defineMacro("\\@ifnextchar", function(context) {
    const args = context.consumeArgs(3);  // symbol, if, else
    const nextToken = context.future();
    if (args[0].length === 1 && args[0][0].text === nextToken.text) {
        return {tokens: args[1], numArgs: 0};
    } else {
        return {tokens: args[2], numArgs: 0};
    }
});

// LaTeX's \@ifstar{#1}{#2} looks ahead to the next (unexpanded) symbol.
// If it is `*`, then it consumes the symbol, and the macro expands to #1;
// otherwise, the macro expands to #2 (without consuming the symbol).
// TeX source: \def\@ifstar#1{\@ifnextchar *{\@firstoftwo{#1}}}
defineMacro("\\@ifstar", "\\@ifnextchar *{\\@firstoftwo{#1}}");

// LaTeX's \TextOrMath{#1}{#2} expands to #1 in text mode, #2 in math mode
defineMacro("\\TextOrMath", function(context) {
    const args = context.consumeArgs(2);
    if (context.mode === 'text') {
        return {tokens: args[0], numArgs: 0};
    } else {
        return {tokens: args[1], numArgs: 0};
    }
});

//////////////////////////////////////////////////////////////////////
// basics
defineMacro("\\bgroup", "{");
defineMacro("\\egroup", "}");
defineMacro("\\begingroup", "{");
defineMacro("\\endgroup", "}");

// Unicode double-struck letters
defineMacro("\u2102", "\\mathbb{C}");
defineMacro("\u210D", "\\mathbb{H}");
defineMacro("\u2115", "\\mathbb{N}");
defineMacro("\u2119", "\\mathbb{P}");
defineMacro("\u211A", "\\mathbb{Q}");
defineMacro("\u211D", "\\mathbb{R}");
defineMacro("\u2124", "\\mathbb{Z}");

// Unicode middle dot
// The KaTeX fonts do not contain U+00B7. Instead, \cdotp displays
// the dot at U+22C5 and gives it punct spacing.
defineMacro("\u00b7", "\\cdotp");

// \llap and \rlap render their contents in text mode
defineMacro("\\llap", "\\mathllap{\\textrm{#1}}");
defineMacro("\\rlap", "\\mathrlap{\\textrm{#1}}");
defineMacro("\\clap", "\\mathclap{\\textrm{#1}}");

//////////////////////////////////////////////////////////////////////
// amsmath.sty
// http://mirrors.concertpass.com/tex-archive/macros/latex/required/amsmath/amsmath.pdf

// \def\overset#1#2{\binrel@{#2}\binrel@@{\mathop{\kern\z@#2}\limits^{#1}}}
defineMacro("\\overset", "\\mathop{#2}\\limits^{#1}");
defineMacro("\\underset", "\\mathop{#2}\\limits_{#1}");

// \newcommand{\boxed}[1]{\fbox{\m@th$\displaystyle#1$}}
defineMacro("\\boxed", "\\fbox{\\displaystyle{#1}}");

// \def\iff{\DOTSB\;\Longleftrightarrow\;}
// \def\implies{\DOTSB\;\Longrightarrow\;}
// \def\impliedby{\DOTSB\;\Longleftarrow\;}
defineMacro("\\iff", "\\DOTSB\\;\\Longleftrightarrow\\;");
defineMacro("\\implies", "\\DOTSB\\;\\Longrightarrow\\;");
defineMacro("\\impliedby", "\\DOTSB\\;\\Longleftarrow\\;");

// AMSMath's automatic \dots, based on \mdots@@ macro.
const dotsByToken = {
    ',': '\\dotsc',
    '\\not': '\\dotsb',
    // \keybin@ checks for the following:
    '+': '\\dotsb',
    '=': '\\dotsb',
    '<': '\\dotsb',
    '>': '\\dotsb',
    '-': '\\dotsb',
    '*': '\\dotsb',
    ':': '\\dotsb',
    // Symbols whose definition starts with \DOTSB:
    '\\DOTSB': '\\dotsb',
    '\\coprod': '\\dotsb',
    '\\bigvee': '\\dotsb',
    '\\bigwedge': '\\dotsb',
    '\\biguplus': '\\dotsb',
    '\\bigcap': '\\dotsb',
    '\\bigcup': '\\dotsb',
    '\\prod': '\\dotsb',
    '\\sum': '\\dotsb',
    '\\bigotimes': '\\dotsb',
    '\\bigoplus': '\\dotsb',
    '\\bigodot': '\\dotsb',
    '\\bigsqcup': '\\dotsb',
    '\\implies': '\\dotsb',
    '\\impliedby': '\\dotsb',
    '\\And': '\\dotsb',
    '\\longrightarrow': '\\dotsb',
    '\\Longrightarrow': '\\dotsb',
    '\\longleftarrow': '\\dotsb',
    '\\Longleftarrow': '\\dotsb',
    '\\longleftrightarrow': '\\dotsb',
    '\\Longleftrightarrow': '\\dotsb',
    '\\mapsto': '\\dotsb',
    '\\longmapsto': '\\dotsb',
    '\\hookrightarrow': '\\dotsb',
    '\\iff': '\\dotsb',
    '\\doteq': '\\dotsb',
    // Symbols whose definition starts with \mathbin:
    '\\mathbin': '\\dotsb',
    '\\bmod': '\\dotsb',
    // Symbols whose definition starts with \mathrel:
    '\\mathrel': '\\dotsb',
    '\\relbar': '\\dotsb',
    '\\Relbar': '\\dotsb',
    '\\xrightarrow': '\\dotsb',
    '\\xleftarrow': '\\dotsb',
    // Symbols whose definition starts with \DOTSI:
    '\\DOTSI': '\\dotsi',
    '\\int': '\\dotsi',
    '\\oint': '\\dotsi',
    '\\iint': '\\dotsi',
    '\\iiint': '\\dotsi',
    '\\iiiint': '\\dotsi',
    '\\idotsint': '\\dotsi',
    // Symbols whose definition starts with \DOTSX:
    '\\DOTSX': '\\dotsx',
};

defineMacro("\\dots", function(context) {
    // TODO: If used in text mode, should expand to \textellipsis.
    // However, in KaTeX, \textellipsis and \ldots behave the same
    // (in text mode), and it's unlikely we'd see any of the math commands
    // that affect the behavior of \dots when in text mode.  So fine for now
    // (until we support \ifmmode ... \else ... \fi).
    let thedots = '\\dotso';
    const next = context.expandAfterFuture().text;
    if (next in dotsByToken) {
        thedots = dotsByToken[next];
    } else if (next.substr(0, 4) === '\\not') {
        thedots = '\\dotsb';
    } else if (next in symbols.math) {
        if (utils.contains(['bin', 'rel'], symbols.math[next].group)) {
            thedots = '\\dotsb';
        }
    }
    return thedots;
});

const spaceAfterDots = {
    // \rightdelim@ checks for the following:
    ')': true,
    ']': true,
    '\\rbrack': true,
    '\\}': true,
    '\\rbrace': true,
    '\\rangle': true,
    '\\rceil': true,
    '\\rfloor': true,
    '\\rgroup': true,
    '\\rmoustache': true,
    '\\right': true,
    '\\bigr': true,
    '\\biggr': true,
    '\\Bigr': true,
    '\\Biggr': true,
    // \extra@ also tests for the following:
    '$': true,
    // \extrap@ checks for the following:
    ';': true,
    '.': true,
    ',': true,
};

defineMacro("\\dotso", function(context) {
    const next = context.future().text;
    if (next in spaceAfterDots) {
        return "\\ldots\\,";
    } else {
        return "\\ldots";
    }
});

defineMacro("\\dotsc", function(context) {
    const next = context.future().text;
    // \dotsc uses \extra@ but not \extrap@, instead specially checking for
    // ';' and '.', but doesn't check for ','.
    if (next in spaceAfterDots && next !== ',') {
        return "\\ldots\\,";
    } else {
        return "\\ldots";
    }
});

defineMacro("\\cdots", function(context) {
    const next = context.future().text;
    if (next in spaceAfterDots) {
        return "\\@cdots\\,";
    } else {
        return "\\@cdots";
    }
});

defineMacro("\\dotsb", "\\cdots");
defineMacro("\\dotsm", "\\cdots");
defineMacro("\\dotsi", "\\!\\cdots");
// amsmath doesn't actually define \dotsx, but \dots followed by a macro
// starting with \DOTSX implies \dotso, and then \extra@ detects this case
// and forces the added `\,`.
defineMacro("\\dotsx", "\\ldots\\,");

// \let\DOTSI\relax
// \let\DOTSB\relax
// \let\DOTSX\relax
defineMacro("\\DOTSI", "\\relax");
defineMacro("\\DOTSB", "\\relax");
defineMacro("\\DOTSX", "\\relax");

// http://texdoc.net/texmf-dist/doc/latex/amsmath/amsmath.pdf
defineMacro("\\thinspace", "\\,");    //   \let\thinspace\,
defineMacro("\\medspace", "\\:");     //   \let\medspace\:
defineMacro("\\thickspace", "\\;");   //   \let\thickspace\;

//////////////////////////////////////////////////////////////////////
// LaTeX source2e

// \def\TeX{T\kern-.1667em\lower.5ex\hbox{E}\kern-.125emX\@}
// TODO: Doesn't normally work in math mode because \@ fails.  KaTeX doesn't
// support \@ yet, so that's omitted, and we add \text so that the result
// doesn't look funny in math mode.
defineMacro("\\TeX", "\\textrm{T\\kern-.1667em\\raisebox{-.5ex}{E}\\kern-.125emX}");

// \DeclareRobustCommand{\LaTeX}{L\kern-.36em%
//         {\sbox\z@ T%
//          \vbox to\ht\z@{\hbox{\check@mathfonts
//                               \fontsize\sf@size\z@
//                               \math@fontsfalse\selectfont
//                               A}%
//                         \vss}%
//         }%
//         \kern-.15em%
//         \TeX}
// This code aligns the top of the A with the T (from the perspective of TeX's
// boxes, though visually the A appears to extend above slightly).
// We compute the corresponding \raisebox when A is rendered at \scriptsize,
// which is size3, which has a scale factor of 0.7 (see Options.js).
const latexRaiseA = fontMetricsData['Main-Regular']["T".charCodeAt(0)][1] -
    0.7 * fontMetricsData['Main-Regular']["A".charCodeAt(0)][1] + "em";
defineMacro("\\LaTeX",
    `\\textrm{L\\kern-.36em\\raisebox{${latexRaiseA}}{\\scriptsize A}` +
    "\\kern-.15em\\TeX}");

// New KaTeX logo based on tweaking LaTeX logo
defineMacro("\\KaTeX",
    `\\textrm{K\\kern-.17em\\raisebox{${latexRaiseA}}{\\scriptsize A}` +
    "\\kern-.15em\\TeX}");

// \DeclareRobustCommand\hspace{\@ifstar\@hspacer\@hspace}
// \def\@hspace#1{\hskip  #1\relax}
// KaTeX doesn't do line breaks, so \hspace and \hspace* are the same as \kern
defineMacro("\\hspace", "\\@ifstar\\kern\\kern");

//////////////////////////////////////////////////////////////////////
// mathtools.sty

//\providecommand\ordinarycolon{:}
defineMacro("\\ordinarycolon", ":");
//\def\vcentcolon{\mathrel{\mathop\ordinarycolon}}
//TODO(edemaine): Not yet centered. Fix via \raisebox or #726
defineMacro("\\vcentcolon", "\\mathrel{\\mathop\\ordinarycolon}");
// \providecommand*\dblcolon{\vcentcolon\mathrel{\mkern-.9mu}\vcentcolon}
defineMacro("\\dblcolon", "\\vcentcolon\\mathrel{\\mkern-.9mu}\\vcentcolon");
// \providecommand*\coloneqq{\vcentcolon\mathrel{\mkern-1.2mu}=}
defineMacro("\\coloneqq", "\\vcentcolon\\mathrel{\\mkern-1.2mu}=");
// \providecommand*\Coloneqq{\dblcolon\mathrel{\mkern-1.2mu}=}
defineMacro("\\Coloneqq", "\\dblcolon\\mathrel{\\mkern-1.2mu}=");
// \providecommand*\coloneq{\vcentcolon\mathrel{\mkern-1.2mu}\mathrel{-}}
defineMacro("\\coloneq", "\\vcentcolon\\mathrel{\\mkern-1.2mu}\\mathrel{-}");
// \providecommand*\Coloneq{\dblcolon\mathrel{\mkern-1.2mu}\mathrel{-}}
defineMacro("\\Coloneq", "\\dblcolon\\mathrel{\\mkern-1.2mu}\\mathrel{-}");
// \providecommand*\eqqcolon{=\mathrel{\mkern-1.2mu}\vcentcolon}
defineMacro("\\eqqcolon", "=\\mathrel{\\mkern-1.2mu}\\vcentcolon");
// \providecommand*\Eqqcolon{=\mathrel{\mkern-1.2mu}\dblcolon}
defineMacro("\\Eqqcolon", "=\\mathrel{\\mkern-1.2mu}\\dblcolon");
// \providecommand*\eqcolon{\mathrel{-}\mathrel{\mkern-1.2mu}\vcentcolon}
defineMacro("\\eqcolon", "\\mathrel{-}\\mathrel{\\mkern-1.2mu}\\vcentcolon");
// \providecommand*\Eqcolon{\mathrel{-}\mathrel{\mkern-1.2mu}\dblcolon}
defineMacro("\\Eqcolon", "\\mathrel{-}\\mathrel{\\mkern-1.2mu}\\dblcolon");
// \providecommand*\colonapprox{\vcentcolon\mathrel{\mkern-1.2mu}\approx}
defineMacro("\\colonapprox", "\\vcentcolon\\mathrel{\\mkern-1.2mu}\\approx");
// \providecommand*\Colonapprox{\dblcolon\mathrel{\mkern-1.2mu}\approx}
defineMacro("\\Colonapprox", "\\dblcolon\\mathrel{\\mkern-1.2mu}\\approx");
// \providecommand*\colonsim{\vcentcolon\mathrel{\mkern-1.2mu}\sim}
defineMacro("\\colonsim", "\\vcentcolon\\mathrel{\\mkern-1.2mu}\\sim");
// \providecommand*\Colonsim{\dblcolon\mathrel{\mkern-1.2mu}\sim}
defineMacro("\\Colonsim", "\\dblcolon\\mathrel{\\mkern-1.2mu}\\sim");

//////////////////////////////////////////////////////////////////////
// colonequals.sty

// Alternate names for mathtools's macros:
defineMacro("\\ratio", "\\vcentcolon");
defineMacro("\\coloncolon", "\\dblcolon");
defineMacro("\\colonequals", "\\coloneqq");
defineMacro("\\coloncolonequals", "\\Coloneqq");
defineMacro("\\equalscolon", "\\eqqcolon");
defineMacro("\\equalscoloncolon", "\\Eqqcolon");
defineMacro("\\colonminus", "\\coloneq");
defineMacro("\\coloncolonminus", "\\Coloneq");
defineMacro("\\minuscolon", "\\eqcolon");
defineMacro("\\minuscoloncolon", "\\Eqcolon");
// \colonapprox name is same in mathtools and colonequals.
defineMacro("\\coloncolonapprox", "\\Colonapprox");
// \colonsim name is same in mathtools and colonequals.
defineMacro("\\coloncolonsim", "\\Colonsim");

// Additional macros, implemented by analogy with mathtools definitions:
defineMacro("\\simcolon", "\\sim\\mathrel{\\mkern-1.2mu}\\vcentcolon");
defineMacro("\\simcoloncolon", "\\sim\\mathrel{\\mkern-1.2mu}\\dblcolon");
defineMacro("\\approxcolon", "\\approx\\mathrel{\\mkern-1.2mu}\\vcentcolon");
defineMacro("\\approxcoloncolon",
            "\\approx\\mathrel{\\mkern-1.2mu}\\dblcolon");

// Present in newtxmath, pxfonts and txfonts
// TODO: The unicode character U+220C ∌ should be added to the font, and this
//       macro turned into a propper defineSymbol in symbols.js. That way, the
//       MathML result will be much cleaner.
defineMacro("\\notni", "\\not\\ni");
defineMacro("\\limsup", "\\DOTSB\\mathop{\\operatorname{lim\\,sup}}\\limits");
defineMacro("\\liminf", "\\DOTSB\\mathop{\\operatorname{lim\\,inf}}\\limits");