/**************************************************************************************************
 * copyright: Copyright (c) 2007-2008 Diggory Hardy.
 *
 * author: Diggory Hardy, diggory.hardy@gmail.com
 *
 * license: BSD style: $(LICENSE)
 *
 * This contains templates for converting a char[] to various data-types.
 *
 * parseTo is roughly the inverse of $(B parseFrom) and should read any data output by $(B parseFrom).
 * It is also available in tango.scrapple.
 *
 * This module basically implements the following templated function for most basic D types:
 * bool, byte, short, int, long, ubyte, ushort, uint, ulong, float, double, real, char.
 * It also supports arrays and associative arrays of any supported type (including of other arrays)
 * and has special handling for strings (char[]) and binary (ubyte[]) data-types.
 * -----------------------------
 * T parseTo(T) (char[] source);
 * -----------------------------
 *
 * $(I source) is the string to parse, and data of the templated type that is read from the string
 * is returned. See the examples to get a better idea of its use.
 *
 * Syntax:
 * The syntax for parsing $(I source) is mostly the same used by D without any prefixes/suffixes
 * (except 0x, 0b & 0o base specifiers). Also a special ubyte[] syntax is supported; see examples.
 * The following escape sequences are supported for strings and characters: \' \" \\
 * \a \b \f \n \r \t \v . Associative array literals use the same syntax as D, described here:
 * $(LINK http://www.digitalmars.com/d/2.0/expression.html#AssocArrayLiteral). All whitespace is
 * ignored (except of course within strings).
 *
 * There are also some public utility functions with their own documentation.
 *
 * Throws:
 * On errors, a ParseException or a UnicodeException (both extend TextException) is thrown with a
 * suitable message. No other exceptions should be thrown.
 *
 * Remarks:
 * There is currently no support for reading wchar/dchar strings. There are, however, unicode
 * conversions for converting UTF-8 to UTF-16/32. Be careful if converting on a char-by-char basis;
 * such conversions cannot be used for non-ascii characters.
 *
 * Examples:
 * ------------------------------------------------------------------------------------------------
 * // Basic examples:
 * ulong        a = parseTo!(ulong) ("20350");
 * float        d = parseTo!(float) ("  1.2e-9 ");
 * int[]        b = parseTo!(int[]) ("[0,1,2,3]");
 *
 * // String and char[] syntax:
 * char[]       c = parseTo!(char[]) ("\"A string\"");
 * char[]       e = parseTo!(char[]) ("['a','n','o','t','h','e','r', ' ' ,'s','t','r','i','n','g']");
 *
 * // These be used interchangably; here's a more complex example of an associative array:
 * bool[char[]] f = parseTo!(bool[char[]]) ("[ \"one\":true, ['t','w','o']:false, \"three\":1, \"four\":000 ]");
 *
 * // There is also a special notation for ubyte[] types:
 * // The digits following 0x must be in pairs and each specify one ubyte.
 * assert ( parseTo!(ubyte[]) (`0x01F2AC`) == parseTo!(ubyte[]) (`[01 ,0xF2, 0xAC]`) );
 *
 * // There's no limit to the complexity!
 * char[char[][][][char]][bool] z = ...; // don't expect me to write this!
 * ------------------------------------------------------------------------------------------------
 *************************************************************************************************/

module mde.mergetag.parse.parseTo;

// tango imports
import tango.core.Exception : TextException, UnicodeException;
import cInt = tango.text.convert.Integer;
import cFloat = tango.text.convert.Float;
import Utf = tango.text.convert.Utf;
import Util = tango.text.Util;

/**
 * Base class for parseTo exceptions.
 */
class ParseException : TextException
{
    this( char[] msg )
    {
        super( msg );
    }
}


//BEGIN parseTo templates

// Associative arrays

const char[] AA_ERR = "Invalid associative array: ";
T[S] parseTo(T : T[S], S) (char[] src) {
    src = Util.trim(src);
    if (src.length < 2 || src[0] != '[' || src[$-1] != ']')
        throw new ParseException (AA_ERR ~ "not [ ... ]");	// bad braces.
    
    T[S] ret;
    foreach (char[] pair; split (src[1..$-1])) {
        uint i = 0;
        while (i < pair.length) {	// advance to the ':'
            char c = pair[i];
            if (c == ':') break;
            if (c == '\'' || c == '"') {	// string or character
                ++i;
                while (i < pair.length && pair[i] != c) {
                    if (pair[i] == '\\') {
                        if (i+2 >= pair.length) throw new ParseException (AA_ERR ~ "unfinished escape sequence within string/char");
                        ++i;	// escape seq.
                    }
                    ++i;
                }
                if (i == pair.length) {
                    throw new ParseException (AA_ERR ~ "encountered [ ... KEY] (missing :DATA)");
                }
            }
            ++i;
        }
        if (i == pair.length) {
            throw new ParseException (AA_ERR ~ "encountered [ ... KEY:] (missing DATA)");
        }
        ret[parseTo!(S) (pair[0..i])] = parseTo!(T) (pair[i+1..$]);
    }
    return ret;
}
debug (UnitTest) unittest {
    char[][char] X = parseTo!(char[][char]) (`['a':"animal", 'b':['b','u','s']]`);
    char[][char] Y = ['a':cast(char[])"animal", 'b':['b','u','s']];
    
    //FIXME: when the compiler's fixed: http://d.puremagic.com/issues/show_bug.cgi?id=1671
    // just assert (X == Y)
    assert (X.length == Y.length);
    assert (X.keys == Y.keys);
    assert (X.values == Y.values);
    //X.rehash; Y.rehash;	// doesn't make a difference
    //assert (X == Y);		// fails (compiler bug)
}


// Arrays

T[] parseTo(T : T[]) (char[] src) {
    src = Util.trim(src);
    if (src.length >= 2 && src[0] == '[' && src[$-1] == ']') return toArray!(T[]) (src);
    throw new ParseException ("Invalid array: not [x, ..., z]");
}

// String (array special case)
T parseTo(T : char[]) (char[] src) {
    src = Util.trim(src);
    if (src.length >= 2 && src[0] == '"' && src[$-1] == '"') {
        src = src[1..$-1];
        T ret;
        ret.length = src.length;	// maximum length; retract to actual length later
        uint i = 0;
        for (uint t = 0; t < src.length;) {
            // process a block of non-escaped characters
            uint s = t;
            while (t < src.length && src[t] != '\\') ++t;	// non-escaped characters
            uint j = i + t - s;
            ret[i..j] = src[s..t];	// copy a block
            i = j;
            
            // process a block of escaped characters
            while (t < src.length && src[t] == '\\') {
                t++;
                if (t == src.length) throw new ParseException ("Invalid string: ends \\\" !");	// next char is "
                ret[i++] = replaceEscapedChar (src[t++]);	// throws if it's invalid
            }
        }
        return ret[0..i];
    }
    else if (src.length >= 2 && src[0] == '[' && src[$-1] == ']') return toArray!(T) (src);
    throw new ParseException ("Invalid string: not quoted (\"*\") or char array (['a',...,'c'])");
}
// Unicode conversions for strings:
T parseTo(T : wchar[]) (char[] src) {
    // May throw a UnicodeException; don't bother catching and rethrowing:
    return Utf.toString16 (parseTo!(char[]) (src));
}
T parseTo(T : dchar[]) (char[] src) {
    // May throw a UnicodeException; don't bother catching and rethrowing:
    return Utf.toString32 (parseTo!(char[]) (src));
}

// Binary (array special case)
T parseTo(T : ubyte[]) (char[] src) {
    src = Util.trim(src);
    // Standard case:
    if (src.length >= 2 && src[0] == '[' && src[$-1] == ']') return toArray!(T) (src);
    // Special case: sequence of hex digits, each pair of which is a ubyte
    if (src.length >= 2 && src[0..2] == "0x") {
        src = src[2..$];    // strip down to actual digits
        
        // Must be in pairs:
        if (src.length % 2 == 1) throw new ParseException ("Invalid binary: odd number of chars");
        
        T ret;
        ret.length = src.length / 2;	// exact
        
        for (uint i, pos; pos + 1 < src.length; ++i) {
            ubyte x = readHexChar(src, pos) << 4;
            x |= readHexChar(src, pos);
            ret[i] = x;
        }
        return ret;
    }
    else throw new ParseException ("Invalid ubyte[]: not an array and doesn't start 0x");
}

debug (UnitTest) unittest {
    assert (parseTo!(double[]) (`[1.0,1.0e-10]`) == [1.0, 1.0e-10]);   // generic array stuff
    assert (parseTo!(double[]) (`[     ]`) == cast(double[]) []);      // empty array
    
    // char[] and char conversions, with commas, escape sequences and multichar UTF8 characters:
    assert (parseTo!(char[][]) (`[ ".\"", [',','\''] ,"!\b€" ]`) == [ ".\"".dup, [',','\''] ,"!\b€" ]);
    
    // wchar[] and dchar[] conversions:
    // The characters were pretty-much pulled at random from unicode tables.
    // The last few cause some wierd (display only) effects in my editor.
    assert (parseTo!(wchar[]) ("\"Test string: ¶α؟अกሀ搀\"") == "Test string: ¶α؟अกሀ搀"w);
    assert (parseTo!(dchar[]) ("\"Test string: ¶α؟अกሀ搀\"") == "Test string: ¶α؟अกሀ搀"d);
    
    assert (parseTo!(ubyte[]) (`0x01F2AC`) == cast(ubyte[]) [0x01, 0xF2, 0xAC]);	// ubyte[] special notation
    assert (parseTo!(ubyte[]) (`[01 ,0xF2, 0xAC]`) == cast(ubyte[]) [0x01, 0xF2, 0xAC]);	// ubyte[] std notation
}


// Basic types

// Char
T parseTo(T : char) (char[] src) {
    src = Util.trim(src);
    if (src.length < 3 || src[0] != '\'' || src[$-1] != '\'')
        throw new ParseException ("Invalid char: not quoted (e.g. 'c')");
    if (src[1] != '\\' && src.length == 3) return src[1];	// Either non escaped
    if (src.length == 4) return replaceEscapedChar (src[2]);	// Or escaped
    
    // Report various errors; warnings for likely and difficult to tell cases:
    // Warn in case it's a multibyte UTF-8 character:
    if (src[1] & 0xC0u) throw new UnicodeException ("Invalid char: too long (non-ASCII UTF-8 characters cannot be read as a single character)", 1);
    throw new ParseException ("Invalid char: too long");
}
/* Basic unicode convertions for wide-chars.
* NOTE: c > 127 signals the start of a multibyte UTF-8 sequence which must be converted for
* UTF-16/32. But since we don't know what the next bytes are we can't do the conversion. */
const char[] WIDE_CHAR_ERROR = "Error: unicode non-ascii character cannot be converted from a single UTF-8 char";
T parseTo(T : wchar) (char[] src) {
    char c = parseTo!(char) (src);
    if (c <= 127u) return cast(wchar) c;	// this char can be converted
    else throw new UnicodeException (WIDE_CHAR_ERROR, 1);
}
T parseTo(T : dchar) (char[] src) {
    char c = parseTo!(char) (src);
    if (c <= 127u) return cast(dchar) c;	// this char can be converted
    else throw new UnicodeException (WIDE_CHAR_ERROR, 1);
}
debug (UnitTest) unittest {
    assert (parseTo!(char) ("\'\\\'\'") == '\'');
    assert (parseTo!(wchar) ("'X'") == 'X');
    assert (parseTo!(dchar) ("'X'") == 'X');
}

// Bool
T parseTo(T : bool) (char[] src) {
    src = Util.trim(src);
    if (src == "true") return true;
    if (src == "false") return false;
    uint pos;
    while (src.length > pos && src[pos] == '0') ++pos;	// skip leading zeros
    if (src.length == pos && pos > 0) return false;
    if (src.length == pos + 1 && src[pos] == '1') return true;
    throw new ParseException ("Invalid bool: not true or false and doesn't evaluate to 0 or 1");
}
debug (UnitTest) unittest {
    assert (parseTo!(bool[]) (`[true,false,01,00]`) == cast(bool[]) [1,0,1,0]);
}

// Ints
T parseTo(T : byte) (char[] src) {
    return toTInt!(T) (src);
}
T parseTo(T : short) (char[] src) {
    return toTInt!(T) (src);
}
T parseTo(T : int) (char[] src) {
    return toTInt!(T) (src);
}
T parseTo(T : long) (char[] src) {
    return toTInt!(T) (src);
}
T parseTo(T : ubyte) (char[] src) {
    return toTInt!(T) (src);
}
T parseTo(T : ushort) (char[] src) {
    return toTInt!(T) (src);
}
T parseTo(T : uint) (char[] src) {
    return toTInt!(T) (src);
}
T parseTo(T : ulong) (char[] src) {
    return toTInt!(T) (src);
}
debug (UnitTest) unittest {
    assert (parseTo!(byte) ("-5") == cast(byte) -5);
    // annoyingly, octal syntax differs from D (blame tango):
    assert (parseTo!(uint[]) ("[0b0100,0o724,0xFa59c,0xFFFFFFFF,0]") == [0b0100u,0724,0xFa59c,0xFFFFFFFF,0]);
}

// Floats
T parseTo(T : float) (char[] src) {
    return toTFloat!(T) (src);
}
T parseTo(T : double) (char[] src) {
    return toTFloat!(T) (src);
}
T parseTo(T : real) (char[] src) {
    return toTFloat!(T) (src);
}
debug (UnitTest) unittest {
    assert (parseTo!(float) ("0.0") == 0.0f);
    assert (parseTo!(double) ("-1e25") == -1e25);
    assert (parseTo!(real) ("5.24e-269") == cast(real) 5.24e-269);
}
//END parseTo templates

//BEGIN Utility funcs
/** Trims whitespace at ends of string and checks for and removes array brackets: []
*
* Throws:
*   ParseException if brackets aren't end non-whitespace characters.
*
* Returns:
*   String without brackets (and whitespace outside those brackets). Useful for passing to split.
*/
char[] stripBrackets (char[] src) {
    src = Util.trim(src);
    if (src.length >= 2 && src[0] == '[' && src[$-1] == ']') return src[1..$-1];
    throw new ParseException ("Invalid bracketed string: not [...]");
}

/** Splits a string into substrings separated by '$(B ,)' with support for characters and strings
 * containing escape sequences and for embedded arrays ($(B [...])).
 *
 * Params:
 *     src A string to separate on commas. Where used for parsing arrays, the brackets enclosing
 *     the array should be removed before calling this function (stripBrackets can do this).
 *
 * Returns:
 *     An array of substrings within src, excluding commas. Whitespace is not stripped and
 *     empty strings may get returned.
 *
 * Remarks:
 *     This function is primarily intended for as a utility function for use by the templates
 *     parsing arrays and associative arrays, but it may be useful in other cases too. Hence the
 *     fact no brackets are stripped from src.
 */
char[][] split (char[] src) {
    src = Util.trim (src);
    if (src == "") return [];		// empty array: no elements when no data
    
    uint depth = 0;			// surface depth (embedded arrays)
    char[][] ret;
    ret.length = src.length / 3;	// unlikely to need a longer array
    uint k = 0;				// current split piece
    uint i = 0, j = 0;			// current read location, start of current piece
    
    while (i < src.length) {
        char c = src[i];
        if (c == '\'' || c == '"') {	// string or character
            ++i;
            while (i < src.length && src[i] != c) {
                if (src[i] == '\\') ++i;	// escape seq.
                ++i;
            }	// Doesn't throw if no terminal quote at end of src, but this should be caught later.
        }
        else if (c == '[') ++depth;
        else if (c == ']') {
            if (depth) --depth;
            else throw new ParseException ("Invalid array literal: closes before end of data item.");
        }
        else if (c == ',' && depth == 0) {		// only if not an embedded array
            if (ret.length <= k) ret.length = ret.length * 2;
            ret[k++] = src[j..i];	// add this piece and increment k
            j = i + 1;
        }
        ++i;
    }
    if (ret.length <= k) ret.length = k + 1;
    ret[k] = src[j..i];		// add final piece (i >= j)
    return ret[0..k+1];
}

/* Templated read-int function to read (un)signed 1-4 byte integers.
 *
 * Actually a reimplementation of tango.text.convert.Integer toLong and parse functions.
 */
private TInt toTInt(TInt) (char[] src) {
    const char[] INT_OUT_OF_RANGE = "Integer out of range";
    bool sign;
    uint radix, ate, ate2;
    
    // Trim off whitespace.
    // NOTE: Cannot use tango.text.convert.Integer.trim to trim leading whitespace since it doesn't
    // treat new-lines, etc. as whitespace which for our purposes is whitespace.
    src = Util.trim (src);
    
    ate = cInt.trim (src, sign, radix);
    if (ate == src.length) throw new ParseException ("Invalid integer: no digits");
    ulong val = cInt.convert (src[ate..$], radix, &ate2);
    ate += ate2;
    
    if (ate < src.length)
        throw new ParseException ("Invalid integer at marked character: \"" ~ src[0..ate] ~ "'" ~ src[ate] ~ "'" ~ src[ate+1..$] ~ "\"");
    
    if (val > TInt.max) throw new ParseException (INT_OUT_OF_RANGE);
    if (sign) {
        long sval = cast(long) -val;
        if (sval > TInt.min) return cast(TInt) sval;
        else throw new ParseException (INT_OUT_OF_RANGE);
    }
    return cast(TInt) val;
}

/* Basically a reimplementation of tango.text.convert.Float.toFloat which checks for
 * whitespace before throwing an exception for overlong input. */
private TFloat toTFloat(TFloat) (char[] src) {
    // NOTE: As for toTInt(), this needs to strip leading as well as trailing whitespace.
    src = Util.trim (src);
    if (src == "") throw new ParseException ("Invalid float: no digits");
    uint ate;
    
    TFloat x = cFloat.parse (src, &ate);
    return x;
}

/* Throws an exception on invalid escape sequences. Supported escape sequences are the following
 * subset of those supported by D: \" \' \\ \a \b \f \n \r \t \v
 */
private char replaceEscapedChar (char c)
{
    // This code was generated:
    if (c <= 'b') {
        if (c <= '\'') {
            if (c == '\"') {
                return '\"';
            } else if (c == '\'') {
                return '\'';
            }
        } else {
            if (c == '\\') {
                return '\\';
            } else if (c == 'a') {
                return '\a';
            } else if (c == 'b') {
                return '\b';
            }
        }
    } else {
        if (c <= 'n') {
            if (c == 'f') {
                return '\f';
            } else if (c == 'n') {
                return '\n';
            }
        } else {
            if (c == 'r') {
                return '\r';
            } else if (c == 't') {
                return '\t';
            } else if (c == 'v') {
                return '\v';
            }
        }
    }
    
    // if we haven't returned:
    throw new ParseException ("Invalid escape sequence: \\"~c);
}

// Reads one hex char: [0-9A-Fa-f]. Otherwise throws an exception. Doesn't check src.length.
private ubyte readHexChar (char[] src, inout uint pos) {
    ubyte x;
    if (src[pos] >= '0' && src[pos] <= '9') x = src[pos] - '0';
    else if (src[pos] >= 'A' && src[pos] <= 'F') x = src[pos] - 'A' + 10;
    else if (src[pos] >= 'a' && src[pos] <= 'f') x = src[pos] - 'a' + 10;
    else throw new ParseException ("Invalid hex digit.");
    ++pos;
    return x;
}

// Generic array reader
// Assumes input is of form "[xxxxx]" (i.e. first and last chars are '[', ']' and length >= 2).
private T[] toArray(T : T[]) (char[] src) {
    T[] ret = new T[16];	// avoid unnecessary allocations
    uint i = 0;
    foreach (char[] element; split(src[1..$-1])) {
        if (i == ret.length) ret.length = ret.length * 2;
        ret[i] = parseTo!(T) (element);
        ++i;
    }
    return ret[0..i];
}

debug (UnitTest) {
    import tango.io.Console;
    
    unittest {
        Cout ("Running unittest: parseTo ...").flush;
        
        assert (parseTo!(char[]) ("\"\\a\\b\\t\\n\\v\\f\\r\\\"\\\'\\\\\"") == "\a\b\t\n\v\f\r\"\'\\");
        
        Cout (" complete").newline;
    }
}
//END Utility funcs