#include "sqrl_internal.h"
#include "SqrlEncoder.h"
#include "SqrlString.h"
#include "SqrlBigInt.h"

namespace libsqrl
{
	SqrlEncoder::SqrlEncoder() : SqrlEncoder( "0123456789abcdef" ) {}

	SqrlEncoder::SqrlEncoder( const char * alphabet ) {
		this->alphabet = alphabet;
		this->reverseMath = true;
	}

	SqrlString *SqrlEncoder::encode( SqrlString *dest, const SqrlString *src, bool append ) {
		if( !src ) return NULL;
		if( !dest ) {
			dest = new SqrlString();
		}
		if( !append ) {
			dest->clear();
		}
		if( src->length() == 0 ) return dest;

		int base = (int)strlen( this->alphabet );
		double cpb = 8.0 / log2(base);
		int zc = 0;
		SqrlBigInt s( src );
		SqrlString ob( (size_t)ceil( src->length() * cpb ) );

		const uint8_t *it = s.cdata();
		const uint8_t *end = s.cdend();
		while( it[0] == 0 && it != end ) {
			zc++;
			it++;
		}
		zc *= (int)ceil(cpb);
		if( this->reverseMath )	s.reverse();

		do {
			ob.push_back( this->alphabet[(s.divideBy(base)) % base] );
		} while( s.length() );

		ob.append( this->alphabet[0], zc );

		if( this->reverseMath ) ob.reverse();
		dest->append( &ob );
		return dest;
	}

	SqrlString *SqrlEncoder::decode( SqrlString *dest, const SqrlString *src, bool append ) {
		if( !src ) return NULL;
		if( !dest ) {
			dest = new SqrlString();
		}
		if( !append ) {
			dest->clear();
		}
		if( src->length() == 0 ) return dest;
		int base = (int)strlen( this->alphabet );

		SqrlString s = SqrlString( src );
		if( !this->reverseMath ) s.reverse();
		SqrlBigInt num = SqrlBigInt();
		const char *ch;
		uint8_t dp;
		size_t leadingZeros = 0;
		size_t cpb = (size_t)ceil( 8.0 / log2(base) );
		const uint8_t *it = s.cdata();
		const uint8_t *end = s.cdend();
		while( it[0] == this->alphabet[0] && it != end ) {
			leadingZeros++;
			it++;
		}
		leadingZeros = leadingZeros / cpb;
		while( it != end ) {
			ch = strchr( this->alphabet, *it );
			if( ch ) {
				dp = (uint8_t)(ch - this->alphabet);
				num.multiplyBy( base );
				num.add( dp );
			}
			it++;
		}
		if( !this->reverseMath ) num.reverse();

		if( leadingZeros ) {
			dest->append( (char)0, leadingZeros );
		}
		dest->append( &num );
		return dest;
	}

	bool SqrlEncoder::validate( const SqrlString *src, size_t *error ) {
		if( !src ) return false;

		const char *it = src->cstring();
		const char *end = src->cstrend();
		while( it != end ) {
			if( !strchr( this->alphabet, *it ) ) {
				if( error ) {
					*error = it - src->cstring();
				}
				return false;
			}
			it++;
		}
		return true;
	}
}