/** Pretty Printing to AsciiDoc, HTML, LaTeX, JIRA Wikitext, etc.
 *
 * Copyright: Per Nordlöw 2018-.
 * License: $(WEB boost.org/LICENSE_1_0.txt, Boost License 1.0).
 * Authors: $(WEB Per Nordlöw)
 *
 * TODO Convert `Viz` param to delegate like for
 * `void toString(scope void delegate(scope const(char)[]) @safe sink)`
 * for independency on arsd.
 *
 * Rename `pp1` to `ppL` and `pp` to `pp1` where relevant to reduce number of
 * template instantiations. And replace multi-calls to viz.pp() to viz.pp1()
 *
 * TODO Add tester that prints types from `nxt.geometry`
 *
 * TODO Remove all restrictions on pp.*Raw.* and call them using ranges such as repeat
 *
 * TODO Use "alias this" on wrapper structures and test!
 *
 * TODO How should std.typecons.Tuple be pretty printed?
 *
 * TODO Add visited member to keeps track of what objects that have been visited
 *
 * TODO Add asGCCMessage pretty prints
 * seq $PATH, ':', $ROW, ':', $COL, ':', message, '[', $TYPE, ']'
 */
module nxt.pretty;

// version = useTerm;

import core.time : Duration;

import std.algorithm.iteration : map;
import std.range.primitives : isInputRange;
import std.traits : isInstanceOf, isSomeString, Unqual, isArray, isIterable;
import std.stdio : stdout;

/* TODO Move logic (toHTML) to these deps and remove these imports */
import nxt.color : Color;
import nxt.mathml;
import nxt.lingua;
import nxt.attributes;
import nxt.rational : Rational;

import arsd.terminal : Terminal, ConsoleOutputType, Bright;

/// See_Also: http://forum.dlang.org/thread/fihymjelvnwfevegwryt@forum.dlang.org#post-fihymjelvnwfevegwryt:40forum.dlang.org
template Concise(Tuple)
{
    static if(isTuple!Tuple)
    {
        struct Concise(Tuple)
        {
            Tuple tup;
            alias tup this;
            // should use a better overload
            string toString() const
            {
                auto app = appender!string(); // TODO use array_ex.Array instead
                app.put(`(`);
                app.put(to!string(concise(tuple[0])));
                foreach (t; tuple.expand[1 .. $])
                {
                    app.put(`, `);
                    app.put(to!string(concise(t)));
                }
                app.put(`)`);
                return app.data;
            }
        }
    }
    else
    {
        alias Concise = Tuple;
    }
}

auto concise(T)(T t) { return Concise!T(t); }

/** Returns: Duration `dur` in a Level-Of-Detail (LOD) string
    representation.
*/
string shortDurationString(in Duration dur) @safe pure nothrow
{
    import std.conv: to;
    immutable weeks = dur.total!`weeks`;
    if (weeks)
    {
        if (weeks < 52)
        {
            return to!string(weeks) ~ ` week` ~ (weeks >= 2 ? `s` : ``);
        }
        else
        {
            immutable years = weeks / 52;
            immutable weeks_rest = weeks % 52;
            return to!string(years) ~ ` year` ~ (years >= 2 ? `s` : ``) ~
            ` and ` ~
            to!string(weeks_rest) ~ ` week` ~ (weeks_rest >= 2 ? `s` : ``);
        }
    }
    immutable days = dur.total!`days`;       if (days)    return to!string(days) ~ ` day` ~ (days >= 2 ? `s` : ``);
    immutable hours = dur.total!`hours`;     if (hours)   return to!string(hours) ~ ` hour` ~ (hours >= 2 ? `s` : ``);
    immutable minutes = dur.total!`minutes`; if (minutes) return to!string(minutes) ~ ` minute` ~ (minutes >= 2 ? `s` : ``);
    immutable seconds = dur.total!`seconds`; if (seconds) return to!string(seconds) ~ ` second` ~ (seconds >= 2 ? `s` : ``);
    immutable msecs = dur.total!`msecs`;     if (msecs) return to!string(msecs) ~ ` millisecond` ~ (msecs >= 2 ? `s` : ``);
    immutable usecs = dur.total!`usecs`;     if (usecs) return to!string(usecs) ~ ` microsecond` ~ (msecs >= 2 ? `s` : ``);
    immutable nsecs = dur.total!`nsecs`;     return to!string(nsecs) ~ ` nanosecond` ~ (msecs >= 2 ? `s` : ``);
}

/** Visual Form(at). */
enum VizForm
{
    textAsciiDoc,               // TODO.
    textAsciiDocUTF8,           // TODO.
    HTML,
    D3js,                       // TODO. See_Also: http://d3js.org/
    LaTeX,                      // TODO.
    jiraWikiMarkup, // TODO. See_Also: https://jira.atlassiana.com/secure/WikiRendererHelpAction.jspa?section=all
    Markdown,       // TODO.
}

/** Solarized light color theme.
 *
 * Each enumerator is an RGB hex string.
 *
 * TODO use RGB-type as enumerator instead
 *
 * See_Also: http://ethanschoonover.com/solarized
 */
enum SolarizedLightColorTheme_hexstring
{
    base00  = `657b83`,
    base01  = `586e75`,
    base02  = `073642`,
    base03  = `002b36`,

    base0   = `839496`,
    base1   = `93a1a1`,
    base2   = `eee8d5`,
    base3   = `fdf6e3`,

    yellow  = `b58900`,
    orange  = `cb4b16`,
    red     = `dc322f`,
    magenta = `d33682`,
    viole   = `6c71c4`,
    blue    = `268bd2`,
    cya     = `2aa198`,
    gree    = `859900`
}

/** HTML tags with no side-effect when its arguments is empty.
    See_Also: http://www.w3schools.com/html/html_formatting.asp
*/
static immutable nonStateHTMLTags = [`b`, `i`, `strong`, `em`, `sub`, `sup`, `small`, `ins`, `del`, `mark`,
                                     `code`, `kbd`, `samp`, `samp`, `var`, `pre`];

static immutable htmlHeader = `<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8"/>
<style>

body { font: 10px Verdana, sans-serif; }
hit0 { background-color:#F2B701; border: solid 0px grey; }
hit1 { background-color:#F18204; border: solid 0px grey; }
hit2 { background-color:#F50035; border: solid 0px grey; }
hit3 { background-color:#F5007A; border: solid 0px grey; }
hit4 { background-color:#A449B6; border: solid 0px grey; }
hit5 { background-color:#3A70BB; border: solid 0px grey; }
hit6 { background-color:#0DE7A6; border: solid 0px grey; }
hit7 { background-color:#70AD48; border: solid 0px grey; }

hit_context { background-color:#c0c0c0; border: solid 0px grey; }

code { background-color:#FFFFE0; }

dlang-byte   { background-color:#FFFFE0; }
dlang-short  { background-color:#FFFFE0; }
dlang-int    { background-color:#FFFFE0; }
dlang-long   { background-color:#FFFFE0; }

dlang-ubyte   { background-color:#FFFFE0; }
dlang-ushort  { background-color:#FFFFE0; }
dlang-uint    { background-color:#FFFFE0; }
dlang-ulong   { background-color:#FFFFE0; }

dlang-bool   { background-color:#FFFFE0; }

dlang-float  { background-color:#FFFFE0; }
dlang-double { background-color:#FFFFE0; }
dlang-real   { background-color:#FFFFE0; }

dlang-char   { background-color:#FFFFE0; }
dlang-wchar  { background-color:#FFFFE0; }
dlang-dchar  { background-color:#FFFFE0; }

dlang-string  { background-color:#FFFFE0; }
dlang-wstring { background-color:#FFFFE0; }
dlang-dstring { background-color:#FFFFE0; }

td, th { border: 1px solid black; }
table { border-collapse: collapse; }

tr:nth-child(even) { background-color: #EBEBEB; }
tr:nth-child(2n+0) { background: #` ~ SolarizedLightColorTheme_hexstring.base2 ~ `; }
tr:nth-child(2n+1) { background: #` ~ SolarizedLightColorTheme_hexstring.base3 ~ `; }

</style>
</head>
<body>
`;

/** Visual Backend.
 */
class Viz
{
    import std.stdio : ioFile = File;

    ioFile outFile;
    Terminal* term;

    bool treeFlag;
    VizForm form;

    bool colorFlag;
    bool flushNewlines = true;

    /* If any (HTML) tags should be ended with a newline.
       This increases the readability of generated HTML code.
     */
    bool newlinedTags = true;

    this(ioFile outFile,
         Terminal* term,
         VizForm form = VizForm.textAsciiDocUTF8,
         bool treeFlag = true,
         bool colorFlag = true,
         bool flushNewlines = true,
         bool newlinedTags = true,
        )
    {
        this.outFile = outFile;
        this.term = term;
        this.treeFlag = treeFlag;
        this.form = form;
        this.colorFlag = colorFlag;
        this.flushNewlines = flushNewlines;
        this.newlinedTags = newlinedTags;
        if (form == VizForm.HTML)
        {
            ppRaw(this, htmlHeader);
        }
    }

    ~this()
    {
        if (form == VizForm.HTML)
        {
            ppRaw("</body>\n</html>");
        }
    }

    /** Put `arg` to `this` without any conversion nor coloring. */
    void ppRaw(T...)(T args)
    {
        foreach (const arg; args)
        {
            if (outFile == stdout)
            {
                term.write(arg); // trick
            }
            else
            {
                outFile.write(arg);
            }
        }
    }

    /** Put `arg` to `this` without any conversion nor coloring. */
    void pplnRaw(T...)(T args)
    {
        foreach (arg; args)
        {
            if (outFile == stdout)
            {
                if (flushNewlines)
                {
                    term.writeln(arg);
                }
                else
                {
                    term.write(arg, '\n');
                }
            }
            else
            {
                if (flushNewlines)
                {
                    outFile.writeln(arg);
                }
                else
                {
                    outFile.write(arg, '\n');
                }
            }
        }
    }

    /// Print opening of tag `tag`.
    void ppTagOpen(T, P...)(T tag, P params)
    {
        if (form == VizForm.HTML)
        {
            ppRaw(`<` ~ tag);
            foreach (param; params)
            {
                ppRaw(' ', param);
            }
            ppRaw(`>`);
        }
    }

    /// Print closing of tag `tag`.
    void ppTagClose(T)(T tag)
    {
        immutable arg = (form == VizForm.HTML) ? `</` ~ tag ~ `>` : tag;
        ppRaw(arg);
    }

    /// Print opening of tag `tag` on a separate line.
    void pplnTagOpen(T)(T tag)
    {
        immutable arg = (form == VizForm.HTML) ? `<` ~ tag ~ `>` : tag;
        if (newlinedTags)
        {
            pplnRaw(arg);
        }
        else
        {
            ppRaw(arg);
        }
    }

    /// Print closing of tag `tag` on a separate line.
    void pplnTagClose(T)(T tag)
    {
        immutable arg = (form == VizForm.HTML) ? `</` ~ tag ~ `>` : tag;
        if (newlinedTags)
        {
            pplnRaw(arg);
        }
        else
        {
            ppRaw(arg);
        }
    }

    /** Put `arg` to `viz` possibly with conversion. */
    void ppPut(T)(T arg,
                  bool nbsp = true)
    {
        if (outFile == stdout)
        {
            term.write(arg);
        }
        else
        {
            if (form == VizForm.HTML)
            {
                import nxt.w3c : encodeHTML;
                outFile.write(arg.encodeHTML(nbsp));
            }
            else
            {
                outFile.write(arg);
            }
        }
    }

    /** Put `arg` to `viz` possibly with conversion. */
    void ppPut(T)(Face face,
                  T arg,
                  bool nbsp = true)
    {
        term.setFace(face, colorFlag);
        ppPut(arg, nbsp);
    }

    /** Print `args` tagged as `tag`. */
    void ppTaggedN(Tag, Args...)(in Tag tag, Args args)
    if (isSomeString!Tag)
    {
        import std.algorithm.searching : find;
        static if (args.length == 1 &&
                   isSomeString!(typeof(args[0])))
        {
            import std.string : empty;
            if (form == VizForm.HTML &&
                args[0].empty &&
                !nonStateHTMLTags.find(tag).empty)
            {
                return;         // skip HTML tags with no content
            }
        }
        if (form == VizForm.HTML) { ppRaw(`<` ~ tag ~ `>`); }
        ppN(args);
        if (form == VizForm.HTML) { ppRaw(`</` ~ tag ~ `>`); }
    }

    /** Print `args` tagged as `tag` on a separate line. */
    void pplnTaggedN(Tag, Args...)(in Tag tag, Args args)
    if (isSomeString!Tag)
    {
        ppTaggedN(tag, args);
        if (newlinedTags)
            pplnRaw(``);
    }

    // TODO Check for MathML support on backend
    @property void ppMathML(SomeIntegral)(Rational!SomeIntegral arg)
    {
        ppTagOpen(`math`);
        ppTagOpen(`mfrac`);
        ppTaggedN(`mi`, arg.numerator);
        ppTaggedN(`mi`, arg.denominator);
        ppTagClose(`mfrac`);
        ppTagClose(`math`);
    }

    /** Pretty-Print Single Argument `arg` to Terminal `term`. */
    void pp1(Arg)(Arg arg)
    {
        pp1(0, arg);
    }

    /** Pretty-Print Single Argument `arg` to Terminal `term`. */
    void pp1(Arg)(int depth,
                  Arg arg)
    {
        static if (is(typeof(ppMathML(arg))))
        {
            if (form == VizForm.HTML)
            {
                return ppMathML(arg);
            }
        }
        static if (is(typeof(arg.toMathML)))
        {
            if (form == VizForm.HTML)
            {
                // TODO Check for MathML support on backend
                return ppRaw(arg.toMathML);
            }
        }
        static if (is(typeof(arg.toHTML)))
        {
            if (form == VizForm.HTML)
            {
                return ppRaw(arg.toHTML);
            }
        }
        static if (is(typeof(arg.toLaTeX)))
        {
            if (form == VizForm.LaTeX)
            {
                return ppRaw(arg.toLaTeX);
            }
        }

        /* TODO Check if any member has mmber toMathML if so call it otherwise call
         * toString. */

        static if (isInstanceOf!(AsWords, Arg))
        {
            foreach (ix, subArg; arg.args)
            {
                static if (ix >= 1)
                    ppRaw(` `); // separator
                pp1(depth + 1, subArg);
            }
        }
        else static if (isInstanceOf!(AsCSL, Arg))
        {
            foreach (ix, subArg; arg.args)
            {
                static if (ix >= 1)
                {
                    pp1(depth + 1, `,`); // separator
                }
                static if (isInputRange!(typeof(subArg)))
                {
                    foreach (subsubArg; subArg)
                    {
                        ppN(subsubArg, `,`);
                    }
                }
            }
        }
        else static if (isInstanceOf!(AsBold, Arg))
        {
            if      (form == VizForm.HTML)
            {
                ppTaggedN(`b`, arg.args);
            }
            else if (form == VizForm.Markdown)
            {
                ppRaw(`**`);
                ppN(arg.args);
                ppRaw(`**`);
            }
        }
        else static if (isInstanceOf!(AsItalic, Arg))
        {
            if      (form == VizForm.HTML)
            {
                ppTaggedN(`i`, arg.args);
            }
            else if (form == VizForm.Markdown)
            {
                ppRaw(`*`);
                ppN(arg.args);
                ppRaw(`*`);
            }
        }
        else static if (isInstanceOf!(AsMonospaced, Arg))
        {
            if      (form == VizForm.HTML)
            {
                ppTaggedN(`tt`, arg.args);
            }
            else if (form == VizForm.jiraWikiMarkup)
            {
                ppRaw(`{{`);
                ppN(arg.args);
                ppRaw(`}}`);
            }
            else if (form == VizForm.Markdown)
            {
                ppRaw('`');
                ppN(arg.args);
                ppRaw('`');
            }
        }
        else static if (isInstanceOf!(AsCode, Arg))
        {
            if      (form == VizForm.HTML)
            {
                /* TODO Use arg.language member to highlight using fs tokenizers
                 * which must be moved out of fs. */
                ppTaggedN(`code`, arg.args);
            }
            else if (form == VizForm.jiraWikiMarkup)
            {
                ppRaw(arg.language ? `{code:` ~ arg.language ~ `}` : `{code}`);
                ppN(arg.args);
                ppRaw(`{code}`);
            }
        }
        else static if (isInstanceOf!(AsEmphasized, Arg))
        {
            if      (form == VizForm.HTML)
            {
                ppTaggedN(`em`, arg.args);
            }
            else if (form == VizForm.jiraWikiMarkup)
            {
                ppRaw(`_`);
                ppN(arg.args);
                ppRaw(`_`);
            }
            else if (form == VizForm.Markdown)
            {
                ppRaw(`_`);
                ppN(arg.args);
                ppRaw(`_`);
            }
        }
        else static if (isInstanceOf!(AsStronglyEmphasized, Arg))
        {
            if (form == VizForm.Markdown)
            {
                ppRaw(`__`);
                ppN(arg.args);
                ppRaw(`__`);
            }
        }
        else static if (isInstanceOf!(AsStrong, Arg))
        {
            if      (form == VizForm.HTML)
            {
                ppTaggedN(`strong`, arg.args);
            }
            else if (form == VizForm.jiraWikiMarkup)
            {
                ppRaw(`*`);
                ppN(arg.args);
                ppRaw(`*`);
            }
        }
        else static if (isInstanceOf!(AsCitation, Arg))
        {
            if      (form == VizForm.HTML)
            {
                ppTaggedN(`cite`, arg.args);
            }
            else if (form == VizForm.jiraWikiMarkup)
            {
                ppRaw(`??`);
                ppN(arg.args);
                ppRaw(`??`);
            }
        }
        else static if (isInstanceOf!(AsDeleted, Arg))
        {
            if      (form == VizForm.HTML)
            {
                ppTaggedN(`deleted`, arg.args);
            }
            else if (form == VizForm.jiraWikiMarkup)
            {
                ppRaw(`-`);
                ppN(arg.args);
                ppRaw(`-`);
            }
        }
        else static if (isInstanceOf!(AsInserted, Arg))
        {
            if      (form == VizForm.HTML)
            {
                ppTaggedN(`inserted`, arg.args);
            }
            else if (form == VizForm.jiraWikiMarkup)
            {
                ppRaw(`+`);
                ppN(arg.args);
                ppRaw(`+`);
            }
        }
        else static if (isInstanceOf!(AsSuperscript, Arg))
        {
            if      (form == VizForm.HTML)
            {
                ppTaggedN(`sup`, arg.args);
            }
            else if (form == VizForm.jiraWikiMarkup)
            {
                ppRaw(`^`);
                ppN(arg.args);
                ppRaw(`^`);
            }
        }
        else static if (isInstanceOf!(AsSubscript, Arg))
        {
            if      (form == VizForm.HTML)
            {
                ppTaggedN(`sub`, arg.args);
            }
            else if (form == VizForm.jiraWikiMarkup)
            {
                ppRaw(`~`);
                ppN(arg.args);
                ppRaw(`~`);
            }
        }
        else static if (isInstanceOf!(AsPreformatted, Arg))
        {
            if      (form == VizForm.HTML)
            {
                pplnTagOpen(`pre`);
                ppN(arg.args);
                pplnTagClose(`pre`);
            }
            else if (form == VizForm.jiraWikiMarkup)
            {
                pplnRaw(`{noformat}`);
                ppN(arg.args);
                pplnRaw(`{noformat}`);
            }
        }
        else static if (isInstanceOf!(AsHeader, Arg))
        {
            if      (form == VizForm.HTML)
            {
                import std.conv: to;
                pplnTaggedN(`h` ~ to!string(arg.level),
                            arg.args);
            }
            else if (form == VizForm.jiraWikiMarkup)
            {
                import std.conv: to;
                ppRaw(`h` ~ to!string(arg.level) ~ `. `);
                ppN(arg.args);
                pplnRaw(``);
            }
            else if (form == VizForm.Markdown)
            {
                foreach (_; 0 .. arg.level) { pp1(0, `#`); }
                ppN(` `, arg.args);
                pplnRaw(``);
            }
            else if (form == VizForm.textAsciiDoc ||
                     form == VizForm.textAsciiDocUTF8)
            {
                ppRaw('\n');
                foreach (_; 0 .. arg.level) { pp1(0, `=`); }
                ppN(' ', arg.args, ' ');
                foreach (_; 0 .. arg.level) { pp1(0, `=`); }
                ppRaw('\n');
            }
        }
        else static if (isInstanceOf!(AsParagraph, Arg))
        {
            if (form == VizForm.HTML)
            {
                pplnTaggedN(`p`, arg.args);
            }
            else if (form == VizForm.LaTeX)
            {
                ppRaw(`\par `);
                pplnTaggedN(arg.args);
            }
            else if (form == VizForm.textAsciiDoc ||
                     form == VizForm.textAsciiDocUTF8)
            {
                ppRaw('\n');
                foreach (_; 0 .. arg.level) { pp1(0, `=`); }
                ppN(` `, arg.args, ` `, tag, '\n');
            }
        }
        else static if (isInstanceOf!(AsBlockquote, Arg))
        {
            if (form == VizForm.HTML)
            {
                pplnTaggedN(`blockquote`, arg.args);
            }
            else if (form == VizForm.jiraWikiMarkup)
            {
                pplnRaw(`{quote}`);
                pplnRaw(arg.args);
                pplnRaw(`{quote}`);
            }
            else if (form == VizForm.Markdown)
            {
                foreach (subArg; arg.args)
                {
                    pplnRaw(`> `, subArg); // TODO Iterate for each line in subArg
                }
            }
        }
        else static if (isInstanceOf!(AsBlockquoteSP, Arg))
        {
            if (form == VizForm.jiraWikiMarkup)
            {
                ppRaw(`bq. `);
                ppN(arg.args);
                pplnRaw(``);
            }
        }
        else static if (is(HorizontalRuler == Arg))
        {
            if (form == VizForm.HTML)
            {
                pplnTagOpen(`hr`);
            }
            if (form == VizForm.jiraWikiMarkup)
            {
                pplnRaw(`----`);
            }
        }
        else static if (isInstanceOf!(MDash, Arg))
        {
            if (form == VizForm.HTML)
            {
                ppRaw(`&mdash;`);
            }
            if (form == VizForm.jiraWikiMarkup ||
                form == VizForm.Markdown ||
                form == VizForm.LaTeX)
            {
                pplnRaw(`---`);
            }
        }
        else static if (isInstanceOf!(AsUList, Arg))
        {
            if (form == VizForm.HTML) { pplnTagOpen(`ul`); }
            else if (form == VizForm.LaTeX) { pplnRaw(`\begin{enumerate}`); }
            ppN(arg.args);
            if (form == VizForm.HTML) { pplnTagClose(`ul`); }
            else if (form == VizForm.LaTeX) { pplnRaw(`\end{enumerate}`); }
        }
        else static if (isInstanceOf!(AsOList, Arg))
        {
            if (form == VizForm.HTML) { pplnTagOpen(`ol`); }
            else if (form == VizForm.LaTeX) { pplnRaw(`\begin{itemize}`); }
            ppN(arg.args);
            if (form == VizForm.HTML) { pplnTagClose(`ol`); }
            else if (form == VizForm.LaTeX) { pplnRaw(`\end{itemize}`); }
        }
        else static if (isInstanceOf!(AsDescription, Arg)) // if args .length == 1 && an InputRange of 2-tuples pairs
        {
            if (form == VizForm.HTML) { pplnTagOpen(`dl`); } // TODO TERM <dt>, DEFINITION <dd>
            else if (form == VizForm.LaTeX) { pplnRaw(`\begin{description}`); } // TODO \item[TERM] DEFINITION
            ppN(arg.args);
            if (form == VizForm.HTML) { pplnTagClose(`dl`); }
            else if (form == VizForm.LaTeX) { pplnRaw(`\end{description}`); }
        }
        else static if (isInstanceOf!(AsTable, Arg))
        {
            if (form == VizForm.HTML)
            {
                const border = (arg.border ? ` border=` ~ arg.border : ``);
                pplnTagOpen(`table` ~ border);
            }
            else if (form == VizForm.LaTeX)
            {
                pplnRaw(`\begin{tabular}`);
            }

            static if (arg.args.length == 1 &&
                       isIterable!(typeof(arg.args[0])))
            {
                auto rows = arg.args[0].asRows();
                rows.recurseFlag = arg.recurseFlag; // propagate
                rows.rowNr = arg.rowNr;
                ppNFlushed(rows);
            }
            else
            {
                ppN(arg.args);
            }

            if (form == VizForm.HTML)
            {
                pplnTagClose(`table`);
            }
            else if (form == VizForm.LaTeX)
            {
                pplnRaw(`\end{tabular}`);
            }
        }
        else static if (isInstanceOf!(AsRows, Arg) &&
                        arg.args.length == 1 &&
                        isIterable!(typeof(arg.args[0])))
        {
            bool capitalizeHeadings = true;

            /* See_Also: http://forum.dlang.org/thread/wjksldfpkpenoskvhsqa@forum.dlang.org#post-jwfildowqrbwtamywsmy:40forum.dlang.org */

            // use aggregate members as header
            import std.range.primitives : ElementType;
            alias Front = ElementType!(typeof(arg.args[0]));
            static if (is(Front == struct) ||
                       is(Front == union) ||
                       is(Front == class) ||
                       is(Front == interface)) // isAggregateType
            {
                /* TODO When __traits(documentation,x)
                   here https://github.com/D-Programming-Language/dmd/pull/3531
                   get merged use it! */
                // pplnTaggedN(`tr`, subArg.asCols); // TODO asItalic
                // Use __traits(allMembers, T) instead
                // Can we lookup file and line of user defined types aswell?

                // member names header.
                if (form == VizForm.HTML) { pplnTagOpen(`tr`); } // TODO Functionize

                // index column
                if      (arg.rowNr == RowNr.offsetZero) pplnTaggedN(`td`, `0-Offset`);
                else if (arg.rowNr == RowNr.offsetOne)  pplnTaggedN(`td`, `1-Offset`);
                foreach (const ix, Member; typeof(Front.tupleof))
                {
                    import std.ascii : isUpper; // TODO support ASCII in fast path and Unicode in slow path
                    import std.string : capitalize;
                    import std.algorithm.iteration : joiner;

                    static      if (is(Memb == struct))    immutable qual = `struct `;
                    else static if (is(Memb == class))     immutable qual = `class `;
                    else static if (is(Memb == enum))      immutable qual = `enum `;
                    else static if (is(Memb == interface)) immutable qual = `interface `;
                    else                                   immutable qual = ``; // TODO Are there more qualifiers

                    import nxt.slicing : preSlicer;
                    immutable idName = __traits(identifier, Front.tupleof[ix]).preSlicer!isUpper.map!capitalize.joiner(` `); // TODO reuse `nxt.casing.camelCasedToLowerSpaced`
                    immutable typeName = Unqual!(Member).stringof; // constness of no interest here

                    pplnTaggedN(`td`,
                                idName.asItalic.asBold,
                                `<br>`,
                                qual.asKeyword,
                                typeName.asType);
                }
                if (form == VizForm.HTML) { pplnTagClose(`tr`); }
            }

            size_t ix = 0;
            foreach (subArg; arg.args[0]) // for each table row
            {
                auto cols = subArg.asCols();
                cols.recurseFlag = arg.recurseFlag; // propagate
                cols.rowNr = arg.rowNr;
                cols.rowIx = ix;
                pplnTaggedN(`tr`, cols); // print columns
                ix++;
            }
        }
        else static if (isInstanceOf!(AsCols, Arg))
        {
            alias T_ = typeof(arg.args[0]);
            if (arg.args.length == 1 &&
                (is(T_ == struct) ||
                 is(T_ == class) ||
                 is(T_ == union) ||
                 is(T_ == interface))) // isAggregateType
            {
                auto args0 = arg.args[0];
                if (form == VizForm.jiraWikiMarkup)
                {
                    /* if (args0.length >= 1) { ppRaw(`|`); } */
                }
                if      (arg.rowNr == RowNr.offsetZero)
                {
                    pplnTaggedN(`td`, arg.rowIx + 0);
                }
                else if (arg.rowNr == RowNr.offsetOne)
                {
                    pplnTaggedN(`td`, arg.rowIx + 1);
                }
                foreach (subArg; args0.tupleof) // for each table column
                {
                    if (form == VizForm.HTML)
                    {
                        pplnTaggedN(`td`, subArg); // each element in aggregate as a column
                    }
                    else if (form == VizForm.jiraWikiMarkup)
                    {
                        /* pp1(subArg); ppRaw(`|`); */
                    }
                }
            }
            else
            {
                pplnTaggedN(`tr`, arg.args);
            }
        }
        else static if (isInstanceOf!(AsRow, Arg))
        {
            string spanArg;
            static if (arg.args.length == 1 &&
                       isInstanceOf!(Span, typeof(arg.args[0])))
            {
                spanArg ~= ` rowspan="` ~ to!string(arg._span) ~ `"`;
            }
            if (form == VizForm.HTML) { pplnTagOpen(`tr` ~ spanArg); }
            ppN(arg.args);
            if (form == VizForm.HTML) { pplnTagClose(`tr`); }
        }
        else static if (isInstanceOf!(AsCell, Arg))
        {
            string spanArg;
            static if (arg.args.length != 0 &&
                       isInstanceOf!(Span, typeof(arg.args[0])))
            {
                spanArg ~= ` colspan="` ~ to!string(arg._span) ~ `"`;
            }
            if (form == VizForm.HTML) { ppTagOpen(`td` ~ spanArg); }
            ppN(arg.args);
            if (form == VizForm.HTML) { pplnTagClose(`td`); }
        }
        else static if (isInstanceOf!(AsTHeading, Arg))
        {
            if (form == VizForm.HTML)
            {
                pplnTagOpen(`th`);
                ppN(arg.args);
                pplnTagClose(`th`);
            }
            else if (form == VizForm.jiraWikiMarkup)
            {
                if (args.length != 0)
                {
                    ppRaw(`||`);
                }
                foreach (subArg; args)
                {
                    pp1(subArg);
                    ppRaw(`||`);
                }
            }
        }
        else static if (isInstanceOf!(AsItem, Arg))
        {
            if (form == VizForm.HTML) { ppTagOpen(`li`); }
            else if (form == VizForm.textAsciiDoc) { ppRaw(` - `); } // if inside ordered list use . instead of -
            else if (form == VizForm.LaTeX) { ppRaw(`\item `); }
            else if (form == VizForm.textAsciiDocUTF8) { ppRaw(` • `); }
            else if (form == VizForm.Markdown) { ppRaw(`* `); } // TODO Alternatively +,-,*, or 1. TODO Need counter for ordered lists
            ppN(arg.args);
            if (form == VizForm.HTML) { pplnTagClose(`li`); }
            else if (form == VizForm.LaTeX) { pplnRaw(``); }
            else if (form == VizForm.textAsciiDoc ||
                     form == VizForm.textAsciiDocUTF8 ||
                     form == VizForm.Markdown) { pplnRaw(``); }
        }
        else static if (isInstanceOf!(AsPath, Arg) ||
                        isInstanceOf!(AsURL, Arg))
        {
            auto vizArg = this;
            vizArg.treeFlag = false;

            enum isString = isSomeString!(typeof(arg.arg)); // only create hyperlink if arg is a string

            static if (isString)
            {
                if (form == VizForm.HTML)
                {
                    static if (isInstanceOf!(AsPath, Arg))
                    {
                        ppTagOpen(`a href="file://` ~ arg.arg ~ `"`);
                    }
                    else static if (isInstanceOf!(AsURL, Arg))
                    {
                        ppTagOpen(`a href="` ~ arg.arg ~ `"`);
                    }
                }
            }

            vizArg.pp1(depth + 1, arg.arg);

            static if (isString)
            {
                if (form == VizForm.HTML)
                {
                    ppTagClose(`a`);
                }
            }
        }
        else static if (isInstanceOf!(AsName, Arg))
        {
            auto vizArg = viz;
            vizArg.treeFlag = true;
            pp1(term, vizArg, depth + 1, arg.arg);
        }
        // else static if (isInstanceOf!(AsHit, Arg))
        // {
        //     const ixs = to!string(arg.ix);
        //     if (form == VizForm.HTML) { ppTagOpen(`hit` ~ ixs); }
        //     pp1(depth + 1, arg.args);
        //     if (form == VizForm.HTML) { ppTagClose(`hit` ~ ixs); }
        // }
        // else static if (isInstanceOf!(AsCtx, Arg))
        // {
        //     if (form == VizForm.HTML) { ppTagOpen(`hit_context`); }
        //     pp1(depth + 1, arg.args);
        //     if (form == VizForm.HTML) { ppTagClose(`hit_context`); }
        // }
        else static if (isArray!Arg &&
                        !isSomeString!Arg)
        {
            ppRaw(`[`);
            foreach (ix, subArg; arg)
            {
                if (ix >= 1)
                    ppRaw(`,`); // separator
                pp1(depth + 1, subArg);
            }
            ppRaw(`]`);
        }
        else static if (isInputRange!Arg)
        {
            foreach (subArg; arg)
            {
                pp1(depth + 1, subArg);
            }
        }
        else static if (__traits(hasMember, arg, `parent`)) // TODO Use isFile = File or NonNull!File
        {
            import std.path: dirSeparator;
            if (form == VizForm.HTML)
            {
                ppRaw(`<a href="file://`);
                ppPut(arg.path);
                ppRaw(`">`);
            }

            if (!treeFlag)
            {
                // write parent path
                foreach (parent; arg.parents)
                {
                    ppPut(dirSeparator);
                    if (form == VizForm.HTML) { ppTagOpen(`b`); }
                    ppPut(dirFace, parent.name);
                    if (form == VizForm.HTML) { ppTagClose(`b`); }
                }
                ppPut(dirSeparator);
            }

            // write name
            static if (__traits(hasMember, arg, `isRoot`)) // TODO Use isDir = Dir or NonNull!Dir
            {
                immutable name = arg.isRoot ? dirSeparator : arg.name ~ dirSeparator;
            }
            else
            {
                immutable name = arg.name;
            }

            if (form == VizForm.HTML)
            {
                // static      if (isSymlink!Arg) { ppTagOpen(`i`); }
                // static if (isDir!Arg) { ppTagOpen(`b`); }
            }

            ppPut(arg.getFace(), name);

            if (form == VizForm.HTML)
            {
                // static      if (isSymlink!Arg) { ppTagClose(`i`); }
                // static if (isDir!Arg) { ppTagClose(`b`); }
            }

            if (form == VizForm.HTML) { ppTagClose(`a`); }
        }
        else
        {
            static if (__traits(hasMember, arg, `path`))
            {
                const arg_string = arg.path;
            }
            else
            {
                import std.conv: to;
                const arg_string = to!string(arg);
            }

            static if (__traits(hasMember, arg, `face`) &&
                       __traits(hasMember, arg.face, `tagsHTML`))
            {
                if (form == VizForm.HTML)
                {
                    foreach (tag; arg.face.tagsHTML)
                    {
                        outFile.write(`<`, tag, `>`);
                    }
                }
            }

            // write
            term.setFace(arg.getFace(), colorFlag);
            if (outFile == stdout)
            {
                term.write(arg_string);
            }
            else
            {
                ppPut(arg.getFace(), arg_string);
            }

            static if (__traits(hasMember, arg, `face`) &&
                       __traits(hasMember, arg.face, `tagsHTML`))
            {
                if (form == VizForm.HTML)
                {
                    foreach (tag; arg.face.tagsHTML)
                    {
                        outFile.write(`</`, tag, `>`);
                    }
                }
            }
        }
    }

    /** Pretty-Print Multiple Arguments `args` to Terminal `term`. */
    void ppN(Args...)(Args args)
    {
        foreach (arg; args)
        {
            pp1(0, arg);
        }
    }

    /** Pretty-Print Arguments `args` to Terminal `term` without Line Termination. */
    void ppNFlushed(Args...)(Args args)
    {
        ppN(args);
        if (outFile == stdout)
        {
            term.flush();
        }
    }

    /** Pretty-Print Arguments `args` including final line termination. */
    void ppln(Args...)(Args args)
    {
        ppN(args);
        if (outFile == stdout)
        {
            term.writeln(lbr(form == VizForm.HTML));
            term.flush();
        }
        else
        {
            outFile.writeln(lbr(form == VizForm.HTML));
        }
    }

    /** Pretty-Print Arguments `args` each including a final line termination. */
    void pplns(Args...)(Args args)
    {
        foreach (arg; args)
        {
            ppln(args);
        }
    }

    /** Print End of Line to Terminal `term`. */
    void ppendl()
    {
        ppln(``);
    }

}

/// Face with color of type `SomeColor`.
struct Face
{
    this(Color foregroundColor,
         Color backgroundColor,
         bool bright = false,
         bool italic = false,
         string[] tagsHTML = [])
    {
        this.foregroundColor = foregroundColor;
        this.backgroundColor = backgroundColor;
        this.bright = bright;
        this.tagsHTML = tagsHTML;
    }
    string[] tagsHTML;
    Color foregroundColor;
    Color backgroundColor;
    bool bright;
    bool italic;
}

// Faces (Font/Color)
enum stdFace = Face(Color.white, Color.black);
enum pathFace = Face(Color.green, Color.black, true);

enum dirFace = Face(Color.blue, Color.black, true);
enum fileFace = Face(Color.magenta, Color.black, true);
enum baseNameFace = fileFace;
enum specialFileFace = Face(Color.red, Color.black, true);
enum regFileFace = Face(Color.white, Color.black, true, false, [`b`]);
enum symlinkFace = Face(Color.cyan, Color.black, true, true, [`i`]);
enum symlinkBrokenFace = Face(Color.red, Color.black, true, true, [`i`]);
enum missingSymlinkTargetFace = Face(Color.red, Color.black, false, true, [`i`]);

enum contextFace = Face(Color.green, Color.black);

enum timeFace = Face(Color.magenta, Color.black);
enum digestFace = Face(Color.yellow, Color.black);

enum infoFace = Face(Color.white, Color.black, true);
enum warnFace = Face(Color.yellow, Color.black);
enum kindFace = warnFace;
enum errorFace = Face(Color.red, Color.black);

enum titleFace = Face(Color.white, Color.black, false, false, [`title`]);
enum h1Face = Face(Color.white, Color.black, false, false, [`h1`]);

// Support these as immutable

/** Key (Hit) Face Palette. */
enum ctxFaces = [Face(Color.red, Color.black),
                 Face(Color.green, Color.black),
                 Face(Color.blue, Color.black),
                 Face(Color.cyan, Color.black),
                 Face(Color.magenta, Color.black),
                 Face(Color.yellow, Color.black),
    ];

/** Key (Hit) Faces. */
enum keyFaces = ctxFaces.map!(a => Face(a.foregroundColor, a.backgroundColor, true));

void setFace(Term, Face)(ref Term term,
                         Face face,
                         bool colorFlag)
{
    if (colorFlag)
    {
        version(useTerm)
        {
            term.color(face.foregroundColor | (face.bright ? Bright : 0) ,
                       face.backgroundColor);
        }
    }
}

/** Fazed (Rich) Text. */
struct Fazed(T)
{
    T text;
    const Face face;
    string toString() const @property pure nothrow
    {
        import std.conv : to;
        return to!string(text);
    }
}
auto faze(T)(T text, in Face face = stdFace) @safe pure nothrow
{
    return Fazed!T(text, face);
}

auto getFace(Arg)(in Arg arg) @safe pure nothrow
{
    // pick face
    static if (__traits(hasMember, arg, `face`))
    {
        return arg.face;
    }
    // else static if (isInstanceOf!(Digest, Arg)) // instead of is(Unqual!(Arg) == SHA1Digest)
    // {
    //     return digestFace;
    // }
    // else static if (isInstanceOf!(AsHit, Arg))
    // {
    //     return keyFaces.cycle[arg.ix];
    // }
    // else static if (isInstanceOf!(AsCtx, Arg))
    // {
    //     return ctxFaces.cycle[arg.ix];
    // }
    else
    {
        return stdFace;
    }
}

/** Show `viz`.
 */
void show(Viz viz)
{
    viz.outFile.flush();
    import std.process : spawnProcess, wait;
    auto pid = spawnProcess([`xdg-open`, viz.outFile.name]);
    assert(wait(pid) == 0);
}

version(unittest)
{
    import std.algorithm.iteration : map;
    // TODO hide these stuff in constructor for Viz
    import std.uuid : randomUUID;
    import std.stdio : File;
    import nxt.rational : rational;
}

unittest
{
    string outPath = `/tmp/fs-` ~ randomUUID.toString() ~ `.` ~ `html`; // reuse `nxt.tempfs`
    File outFile = File(outPath, `w`);

    auto term = Terminal(ConsoleOutputType.linear);

    auto viz = new Viz(outFile, &term, VizForm.HTML);

    viz.pp1(`Pretty Printing`.asH!1);
    viz.pp1(horizontalRuler);

    viz.pp1(`First Heading`.asH!2);
    viz.ppln(`Something first.`);

    viz.pp1(`Second Heading`.asH!2);
    viz.ppln(`Something else.`);

    struct S
    {
        string theUnit;
        int theSuperValue;
    }

    S[] s = [S("meter", 42),
             S("second", 43)];

    viz.pp1("Struct Array".asH!2);
    viz.pp1(s.asTable);

    viz.pp1("Map Struct Array".asH!2);
    viz.pp1(s.map!(_ => S(_.theUnit,
                          _.theSuperValue^^2)).asTable);

    viz.pp1("Rational Number Array".asH!2);
    viz.pp1([rational(11, 13),
             rational(14, 15),
             rational(17, 32)]);

    struct NamedRational
    {
        string name;
        Rational!long value;
    }

    viz.pp1("Named Rational Number Array as Table".asH!2);
    viz.pp1([NamedRational("x", Rational!long(11, 13)),
             NamedRational("y", Rational!long(111, 133)),
             NamedRational("z", Rational!long(1111, 1333))].asTable);

    viz.show();
}