/*
 * pg_text_decoder.c - PG::TextDecoder module
 * $Id: pg_text_decoder.c,v b7f9daeeba29 2014/11/21 19:53:47 lars $
 *
 */

/*
 *
 * Type casts for decoding PostgreSQL string representations to Ruby objects.
 *
 * Decoder classes are defined with pg_define_coder(). This creates a new coder class and
 * assigns a decoder function.
 *
 * Signature of all type cast decoders is:
 *    VALUE decoder_function(t_pg_coder *this, char *val, int len, int tuple, int field, int enc_idx)
 *
 * Params:
 *   this     - The data part of the coder object that belongs to the decoder function.
 *   val, len - The text or binary data to decode. The caller ensures, that the data is
 *              zero terminated ( that is val[len] = 0 ). The memory should be used read
 *              only by the callee.
 *   tuple    - Row of the value within the result set.
 *   field    - Column of the value within the result set.
 *   enc_idx  - Index of the Encoding that any output String should get assigned.
 *
 * Returns:
 *   The type casted Ruby object.
 *
 */

#include "pg.h"
#include "util.h"
#include <inttypes.h>

VALUE rb_mPG_TextDecoder;
static ID s_id_decode;


/*
 * Document-class: PG::TextDecoder::Boolean < PG::SimpleDecoder
 *
 * This is a decoder class for conversion of PostgreSQL boolean type
 * to Ruby true or false values.
 *
 */
static VALUE
pg_text_dec_boolean(t_pg_coder *conv, char *val, int len, int tuple, int field, int enc_idx)
{
	if (len < 1) {
		rb_raise( rb_eTypeError, "wrong data for text boolean converter in tuple %d field %d", tuple, field);
	}
	return *val == 't' ? Qtrue : Qfalse;
}

/*
 * Document-class: PG::TextDecoder::String < PG::SimpleDecoder
 *
 * This is a decoder class for conversion of PostgreSQL text output to
 * to Ruby String object. The output value will have the character encoding
 * set with PG::Connection#internal_encoding= .
 *
 */
VALUE
pg_text_dec_string(t_pg_coder *conv, char *val, int len, int tuple, int field, int enc_idx)
{
	VALUE ret = rb_tainted_str_new( val, len );
	PG_ENCODING_SET_NOCHECK( ret, enc_idx );
	return ret;
}

/*
 * Document-class: PG::TextDecoder::Integer < PG::SimpleDecoder
 *
 * This is a decoder class for conversion of PostgreSQL integer types
 * to Ruby Integer objects.
 *
 */
static VALUE
pg_text_dec_integer(t_pg_coder *conv, char *val, int len, int tuple, int field, int enc_idx)
{
	long i;
	int max_len;

	if( sizeof(i) >= 8 && FIXNUM_MAX >= 1000000000000000000LL ){
		/* 64 bit system can safely handle all numbers up to 18 digits as Fixnum */
		max_len = 18;
	} else if( sizeof(i) >= 4 && FIXNUM_MAX >= 1000000000LL ){
		/* 32 bit system can safely handle all numbers up to 9 digits as Fixnum */
		max_len = 9;
	} else {
		/* unknown -> don't use fast path for int conversion */
		max_len = 0;
	}

	if( len <= max_len ){
		/* rb_cstr2inum() seems to be slow, so we do the int conversion by hand.
		 * This proved to be 40% faster by the following benchmark:
		 *
		 *   conn.type_mapping_for_results = PG::BasicTypeMapForResults.new conn
		 *   Benchmark.measure do
		 *     conn.exec("select generate_series(1,1000000)").values }
		 *   end
		 */
		char *val_pos = val;
		char digit = *val_pos;
		int neg;
		int error = 0;

		if( digit=='-' ){
			neg = 1;
			i = 0;
		}else if( digit>='0' && digit<='9' ){
			neg = 0;
			i = digit - '0';
		} else {
			error = 1;
		}

		while (!error && (digit=*++val_pos)) {
			if( digit>='0' && digit<='9' ){
				i = i * 10 + (digit - '0');
			} else {
				error = 1;
			}
		}

		if( !error ){
			return LONG2FIX(neg ? -i : i);
		}
	}
	/* Fallback to ruby method if number too big or unrecognized. */
	return rb_cstr2inum(val, 10);
}

/*
 * Document-class: PG::TextDecoder::Float < PG::SimpleDecoder
 *
 * This is a decoder class for conversion of PostgreSQL float4 and float8 types
 * to Ruby Float objects.
 *
 */
static VALUE
pg_text_dec_float(t_pg_coder *conv, char *val, int len, int tuple, int field, int enc_idx)
{
	return rb_float_new(strtod(val, NULL));
}

/*
 * Document-class: PG::TextDecoder::Bytea < PG::SimpleDecoder
 *
 * This is a decoder class for conversion of PostgreSQL bytea type
 * to binary String objects.
 *
 */
static VALUE
pg_text_dec_bytea(t_pg_coder *conv, char *val, int len, int tuple, int field, int enc_idx)
{
	unsigned char *to;
	size_t to_len;
	VALUE ret;

	to = PQunescapeBytea( (unsigned char *)val, &to_len);

	ret = rb_tainted_str_new((char*)to, to_len);
	PQfreemem(to);

	return ret;
}

/*
 * Array parser functions are thankfully borrowed from here:
 * https://github.com/dockyard/pg_array_parser
 */
static VALUE
read_array(t_pg_composite_coder *this, int *index, char *c_pg_array_string, int array_string_length, char *word, int enc_idx, int tuple, int field, t_pg_coder_dec_func dec_func)
{
	/* Return value: array */
	VALUE array;
	int word_index = 0;

	/* The current character in the input string. */
	char c;

	/*  0: Currently outside a quoted string, current word never quoted
	*  1: Currently inside a quoted string
	* -1: Currently outside a quoted string, current word previously quoted */
	int openQuote = 0;

	/* Inside quoted input means the next character should be treated literally,
	* instead of being treated as a metacharacter.
	* Outside of quoted input, means that the word shouldn't be pushed to the array,
	* used when the last entry was a subarray (which adds to the array itself). */
	int escapeNext = 0;

	array = rb_ary_new();

	/* Special case the empty array, so it doesn't need to be handled manually inside
	* the loop. */
	if(((*index) < array_string_length) && c_pg_array_string[(*index)] == '}')
	{
		return array;
	}

	for(;(*index) < array_string_length; ++(*index))
	{
		c = c_pg_array_string[*index];
		if(openQuote < 1)
		{
			if(c == this->delimiter || c == '}')
			{
				if(!escapeNext)
				{
					if(openQuote == 0 && word_index == 4 && !strncmp(word, "NULL", word_index))
					{
						rb_ary_push(array, Qnil);
					}
					else
					{
						VALUE val;
						word[word_index] = 0;
						val = dec_func(this->elem, word, word_index, tuple, field, enc_idx);
						rb_ary_push(array, val);
					}
				}
				if(c == '}')
				{
					return array;
				}
				escapeNext = 0;
				openQuote = 0;
				word_index = 0;
			}
			else if(c == '"')
			{
				openQuote = 1;
			}
			else if(c == '{')
			{
				(*index)++;
				rb_ary_push(array, read_array(this, index, c_pg_array_string, array_string_length, word, enc_idx, tuple, field, dec_func));
				escapeNext = 1;
			}
			else
			{
				word[word_index] = c;
				word_index++;
			}
		}
		else if (escapeNext) {
			word[word_index] = c;
			word_index++;
			escapeNext = 0;
		}
		else if (c == '\\')
		{
			escapeNext = 1;
		}
		else if (c == '"')
		{
			openQuote = -1;
		}
		else
		{
			word[word_index] = c;
			word_index++;
		}
	}

	return array;
}

/*
 * Document-class: PG::TextDecoder::Array < PG::CompositeDecoder
 *
 * This is the decoder class for PostgreSQL array types.
 *
 * All values are decoded according to the #elements_type
 * accessor. Sub-arrays are decoded recursively.
 *
 */
static VALUE
pg_text_dec_array(t_pg_coder *conv, char *val, int len, int tuple, int field, int enc_idx)
{
	t_pg_composite_coder *this = (t_pg_composite_coder *)conv;
	t_pg_coder_dec_func dec_func = pg_coder_dec_func(this->elem, 0);
	/* create a buffer of the same length, as that will be the worst case */
	char *word = xmalloc(len + 1);
	int index = 1;

	VALUE return_value = read_array(this, &index, val, len, word, enc_idx, tuple, field, dec_func);
	free(word);
	return return_value;
}

/*
 * Document-class: PG::TextDecoder::Identifier < PG::CompositeDecoder
 *
 * This is the decoder class for PostgreSQL identifiers.
 *
 * Returns an Array of identifiers:
 *   PG::TextDecoder::Identifier.new.decode('schema."table"."column"')
 *      => ["schema", "table", "column"]
 *
 */
static VALUE
pg_text_dec_identifier(t_pg_coder *conv, char *val, int len, int tuple, int field, int enc_idx)
{
	t_pg_composite_coder *this = (t_pg_composite_coder *)conv;
	t_pg_coder_dec_func dec_func = pg_coder_dec_func(this->elem, 0);

	/* Return value: array */
	VALUE array;
	VALUE elem;
	int word_index = 0;
	int index;
	/* Use a buffer of the same length, as that will be the worst case */
	char word[len + 1];

	/* The current character in the input string. */
	char c;

	/*  0: Currently outside a quoted string
	*  1: Currently inside a quoted string, last char was a quote
	*  2: Currently inside a quoted string, last char was no quote */
	int openQuote = 0;

	array = rb_ary_new();

	for(index = 0; index < len; ++index) {
		c = val[index];
		if(c == '.' && openQuote < 2 ) {
			word[word_index] = 0;

			elem = dec_func(conv, word, word_index, tuple, field, enc_idx);
			rb_ary_push(array, elem);

			openQuote = 0;
			word_index = 0;
		} else if(c == '"') {
			if (openQuote == 1) {
				word[word_index] = c;
				word_index++;
				openQuote = 2;
			} else if (openQuote == 2){
				openQuote = 1;
			} else {
				openQuote = 2;
			}
		} else {
			word[word_index] = c;
			word_index++;
		}
	}

	word[word_index] = 0;
	elem = dec_func(conv, word, word_index, tuple, field, enc_idx);
	rb_ary_push(array, elem);

	return array;
}

/*
 * Document-class: PG::TextDecoder::FromBase64 < PG::CompositeDecoder
 *
 * This is a decoder class for conversion of base64 encoded data
 * to it's binary representation. It outputs a binary Ruby String
 * or some other Ruby object, if a #elements_type decoder was defined.
 *
 */
static VALUE
pg_text_dec_from_base64(t_pg_coder *conv, char *val, int len, int tuple, int field, int enc_idx)
{
	t_pg_composite_coder *this = (t_pg_composite_coder *)conv;
	t_pg_coder_dec_func dec_func = pg_coder_dec_func(this->elem, this->comp.format);
	int decoded_len;
	/* create a buffer of the expected decoded length */
	VALUE out_value = rb_tainted_str_new(NULL, BASE64_DECODED_SIZE(len));

	decoded_len = base64_decode( RSTRING_PTR(out_value), val, len );
	rb_str_set_len(out_value, decoded_len);

	/* Is it a pure String conversion? Then we can directly send out_value to the user. */
	if( this->comp.format == 0 && dec_func == pg_text_dec_string ){
		PG_ENCODING_SET_NOCHECK( out_value, enc_idx );
		return out_value;
	}
	if( this->comp.format == 1 && dec_func == pg_bin_dec_bytea ){
		PG_ENCODING_SET_NOCHECK( out_value, rb_ascii8bit_encindex() );
		return out_value;
	}
	out_value = dec_func(this->elem, RSTRING_PTR(out_value), decoded_len, tuple, field, enc_idx);

	return out_value;
}

void
init_pg_text_decoder()
{
	s_id_decode = rb_intern("decode");

	/* This module encapsulates all decoder classes with text input format */
	rb_mPG_TextDecoder = rb_define_module_under( rb_mPG, "TextDecoder" );

	/* Make RDoc aware of the decoder classes... */
	/* dummy = rb_define_class_under( rb_mPG_TextDecoder, "Boolean", rb_cPG_SimpleDecoder ); */
	pg_define_coder( "Boolean", pg_text_dec_boolean, rb_cPG_SimpleDecoder, rb_mPG_TextDecoder );
	/* dummy = rb_define_class_under( rb_mPG_TextDecoder, "Integer", rb_cPG_SimpleDecoder ); */
	pg_define_coder( "Integer", pg_text_dec_integer, rb_cPG_SimpleDecoder, rb_mPG_TextDecoder );
	/* dummy = rb_define_class_under( rb_mPG_TextDecoder, "Float", rb_cPG_SimpleDecoder ); */
	pg_define_coder( "Float", pg_text_dec_float, rb_cPG_SimpleDecoder, rb_mPG_TextDecoder );
	/* dummy = rb_define_class_under( rb_mPG_TextDecoder, "String", rb_cPG_SimpleDecoder ); */
	pg_define_coder( "String", pg_text_dec_string, rb_cPG_SimpleDecoder, rb_mPG_TextDecoder );
	/* dummy = rb_define_class_under( rb_mPG_TextDecoder, "Bytea", rb_cPG_SimpleDecoder ); */
	pg_define_coder( "Bytea", pg_text_dec_bytea, rb_cPG_SimpleDecoder, rb_mPG_TextDecoder );

	/* dummy = rb_define_class_under( rb_mPG_TextDecoder, "Array", rb_cPG_CompositeDecoder ); */
	pg_define_coder( "Array", pg_text_dec_array, rb_cPG_CompositeDecoder, rb_mPG_TextDecoder );
	/* dummy = rb_define_class_under( rb_mPG_TextDecoder, "Identifier", rb_cPG_CompositeDecoder ); */
	pg_define_coder( "Identifier", pg_text_dec_identifier, rb_cPG_CompositeDecoder, rb_mPG_TextDecoder );
	/* dummy = rb_define_class_under( rb_mPG_TextDecoder, "FromBase64", rb_cPG_CompositeDecoder ); */
	pg_define_coder( "FromBase64", pg_text_dec_from_base64, rb_cPG_CompositeDecoder, rb_mPG_TextDecoder );
}
