#include "hstore.h"
#include <ctype.h>

PG_MODULE_MAGIC;

typedef struct {
	char *begin;
	char *ptr;
	char *cur;
	char *word;
	int wordlen;

	Pairs	*pairs;
	int	pcur;
	int	plen;
} HSParser;

#define RESIZEPRSBUF \
do { \
        if ( state->cur - state->word + 1 >= state->wordlen ) \
        { \
                int4 clen = state->cur - state->word; \
                state->wordlen *= 2; \
                state->word = (char*)repalloc( (void*)state->word, state->wordlen ); \
                state->cur = state->word + clen; \
        } \
} while (0)


#define GV_WAITVAL 0 
#define GV_INVAL 1 
#define GV_INESCVAL 2 
#define GV_WAITESCIN 3 
#define GV_WAITESCESCIN 4 

static bool
get_val( HSParser *state, bool ignoreeq, bool *escaped ) {
	int st = GV_WAITVAL;
	state->wordlen=32;
	state->cur = state->word = palloc( state->wordlen );
	*escaped=false;

	while(1) {
		if ( st == GV_WAITVAL ) {
			if ( *(state->ptr) == '"' ) {
				*escaped=true;
				st = GV_INESCVAL;
			} else if ( *(state->ptr) == '\0' ) {
				return false;
			} else if (  *(state->ptr) == '=' && !ignoreeq ) {
				elog(ERROR,"Syntax error near '%c' at postion %d", *(state->ptr), (int4)(state->ptr-state->begin));
			} else if ( *(state->ptr) == '\\' ) {
				st = GV_WAITESCIN;
			} else if ( !isspace(*(state->ptr)) ) {
				*(state->cur) = *(state->ptr);
				state->cur++;
				st = GV_INVAL;
			}
		} else if ( st == GV_INVAL ) {
			if ( *(state->ptr) == '\\' ) {
				st = GV_WAITESCIN;
			} else if ( *(state->ptr) == '=' && !ignoreeq ) {
				state->ptr--;
				return true;
			} else if ( *(state->ptr) == ',' && ignoreeq ) {
				state->ptr--;
				return true;
			} else if ( isspace(*(state->ptr)) ) {
				return true;
			} else if ( *(state->ptr) == '\0' ) {
				state->ptr--;
				return true;
			} else {
				RESIZEPRSBUF;
				*(state->cur) = *(state->ptr);
				state->cur++;
			}
		} else if ( st == GV_INESCVAL ) {
			if ( *(state->ptr) == '\\' ) {
				st = GV_WAITESCESCIN;
			} else if ( *(state->ptr) == '"' ) {
				return true;
			} else if ( *(state->ptr) == '\0' ) {
				elog(ERROR,"Unexpected end of string");
			} else {
				RESIZEPRSBUF;
				*(state->cur) = *(state->ptr);
				state->cur++;
			}
		} else if ( st == GV_WAITESCIN ) {
			if ( *(state->ptr) == '\0' )
				elog(ERROR,"Unexpected end of string");
			RESIZEPRSBUF;
			*(state->cur) = *(state->ptr);
			state->cur++;
			st = GV_INVAL; 
		} else if ( st == GV_WAITESCESCIN ) {
			if ( *(state->ptr) == '\0' )
				elog(ERROR,"Unexpected end of string");
			RESIZEPRSBUF;
			*(state->cur) = *(state->ptr);
			state->cur++;
			st = GV_INESCVAL;
		} else
			elog(ERROR,"Unknown state %d at postion line %d in file '%s'", st, __LINE__, __FILE__); 

		state->ptr++;
	} 

	return false;
}

#define WKEY	0
#define WVAL	1
#define WEQ	2
#define WGT	3
#define WDEL	4


static void
parse_hstore( HSParser *state ) {
	int st = WKEY;
	bool escaped=false;

	state->plen=16;
	state->pairs = (Pairs*)palloc( sizeof(Pairs) * state->plen );
	state->pcur=0;
	state->ptr = state->begin;
	state->word=NULL;

	while(1) {
		if (st == WKEY) {
			if ( !get_val(state, false, &escaped) )
				return;
			if ( state->pcur >= state->plen ) {
				state->plen *= 2;
				state->pairs = (Pairs*)repalloc( state->pairs, sizeof(Pairs) * state->plen );
			}
			state->pairs[ state->pcur ].key = state->word; 
			state->pairs[ state->pcur ].keylen = state->cur - state->word;
			state->pairs[ state->pcur ].val=NULL;
			state->word=NULL;
			st = WEQ;
		} else if ( st == WEQ ) {
			if ( *(state->ptr) == '=' ) {
				st = WGT;
			} else if ( *(state->ptr) == '\0' ) {
				elog(ERROR,"Unexpectd end of string");
			} else if (!isspace(*(state->ptr))) {
				elog(ERROR,"Syntax error near '%c' at postion %d", *(state->ptr), (int4)(state->ptr-state->begin));
			}
		} else if ( st == WGT ) {
			if ( *(state->ptr) == '>' ) {
				st = WVAL;
			} else if ( *(state->ptr) == '\0' ) {
				elog(ERROR,"Unexpectd end of string");
			} else { 
				elog(ERROR,"Syntax error near '%c' at postion %d", *(state->ptr), (int4)(state->ptr-state->begin));
			}
		} else if ( st == WVAL ) {
			if ( !get_val(state, true, &escaped) )
				elog(ERROR,"Unexpected end of string");
			state->pairs[ state->pcur ].val = state->word;
			state->pairs[ state->pcur ].vallen = state->cur - state->word;
			state->pairs[ state->pcur ].isnull = false;
			state->pairs[ state->pcur ].needfree = true;
			if ( state->cur - state->word == 4 && !escaped) {
				state->word[4] = '\0';
				if ( 0==pg_strcasecmp(state->word, "null") ) 
					state->pairs[ state->pcur ].isnull=true;
			} 
			state->word=NULL;
			state->pcur++;
			st = WDEL;
		} else if ( st == WDEL ) {
			if (  *(state->ptr) == ',' ) {
				st = WKEY;
			} else if ( *(state->ptr) == '\0' ) {
				return;
			} else if (!isspace(*(state->ptr))) {
				elog(ERROR,"Syntax error near '%c' at postion %d", *(state->ptr), (int4)(state->ptr-state->begin));
			}
		} else 
			elog(ERROR,"Unknown state %d at line %d in file '%s'", st, __LINE__, __FILE__);

		state->ptr++;
	}
} 

int
comparePairs(const void *a, const void *b) {
	if ( ((Pairs*)a)->keylen == ((Pairs*)b)->keylen ) { 
		int res =  strncmp(
				((Pairs*)a)->key,
				((Pairs*)b)->key,
				((Pairs*)a)->keylen
			);
		if ( res )
			return res;

		/* guarantee that neddfree willl be later */
		if ( ((Pairs*)b)->needfree == ((Pairs*)a)->needfree )
			return 0;
		else if ( ((Pairs*)a)->needfree )
			return 1;
		else
			return -1;  
	}
	return ( ((Pairs*)a)->keylen > ((Pairs*)b)->keylen ) ? 1 : -1;
}

int
uniquePairs(Pairs * a, int4 l, int4 *buflen) {
	Pairs *ptr, *res;

	*buflen=0;
	if ( l < 2 ) {
		if ( l==1 )
			*buflen = a->keylen + ((a->isnull) ? 0 : a->vallen) ;
		return l;
	}

	qsort((void *) a, l, sizeof(Pairs), comparePairs);
	ptr=a+1;
	res=a;	
	while( ptr - a < l ) {
		if ( ptr->keylen == res->keylen && strncmp( ptr->key, res->key, res->keylen )==0 ) {
			if ( ptr->needfree ) {
				pfree(ptr->key);
				pfree(ptr->val);
			}
		} else {
			*buflen += res->keylen + (( res->isnull ) ? 0 : res->vallen);
			res++;
			memcpy(res,ptr,sizeof(Pairs));
		}

		ptr++;
	}

	*buflen += res->keylen + (( res->isnull ) ? 0 : res->vallen);
	return res + 1 - a;
}

static void
freeHSParse(HSParser *state) {
	int i;

	if ( state->word ) pfree( state->word );
	for (i=0;i<state->pcur;i++)
		if ( state->pairs[i].needfree ) {
			if (state->pairs[i].key) pfree(state->pairs[i].key);
			if (state->pairs[i].val) pfree(state->pairs[i].val);
		}
	pfree( state->pairs );
}

PG_FUNCTION_INFO_V1(hstore_in);
Datum           hstore_in(PG_FUNCTION_ARGS);
Datum
hstore_in(PG_FUNCTION_ARGS) {
	HSParser   state;
	int4 len,buflen,i;
	HStore	*out;
	HEntry	*entries;
	char *ptr;

	state.begin =  PG_GETARG_CSTRING(0);

	parse_hstore(&state);

	if ( state.pcur == 0 ) {
		freeHSParse(&state);
		len = CALCDATASIZE(0,0);
		out = palloc(len);
		out->len=len;
		out->size=0;
		PG_RETURN_POINTER(out);
	}

	state.pcur = uniquePairs(state.pairs, state.pcur, &buflen);

	len=CALCDATASIZE(state.pcur, buflen);
	out = palloc(len);
	out->len=len;
	out->size=state.pcur;

	entries=ARRPTR(out);
	ptr = STRPTR(out);

	for(i=0;i<out->size;i++) {
		entries[i].keylen = state.pairs[i].keylen;
		entries[i].pos = ptr - STRPTR(out);
		memcpy(ptr, state.pairs[i].key, state.pairs[i].keylen);
		ptr+=entries[i].keylen;

		entries[i].valisnull = state.pairs[i].isnull;
		if ( entries[i].valisnull )
			entries[i].vallen=4; /* null */
		else {
			entries[i].vallen = state.pairs[i].vallen;
			memcpy(ptr, state.pairs[i].val,state.pairs[i].vallen);
			ptr+=entries[i].vallen;
		}
	}

	freeHSParse(&state);
	PG_RETURN_POINTER(out);
}

static char*
cpw(char *dst, char *src, int len) {
	char *ptr = src;

	while(ptr-src<len) {
		if ( *ptr == '"' || *ptr == '\\' )
			*dst++='\\';
		*dst++ = *ptr++;
	}
	return dst;
}

PG_FUNCTION_INFO_V1(hstore_out);
Datum           hstore_out(PG_FUNCTION_ARGS);
Datum
hstore_out(PG_FUNCTION_ARGS) {
	HStore *in = PG_GETARG_HS(0);
	int buflen,i;
	char *out,*ptr;
	char *base = STRPTR(in);
	HEntry	*entries = ARRPTR(in);

	if ( in->size==0 ) {
		out=palloc(1);
		*out='\0';
		PG_FREE_IF_COPY(in,0);
		PG_RETURN_CSTRING(out);
	}

	buflen = ( 4 /* " */ + 2 /* => */ + 2 /*, */ )*in->size + 
		2 /* esc */ * ( in->len - CALCDATASIZE(in->size,0) );

	out=ptr=palloc(buflen);
	for(i=0;i<in->size;i++) {
		*ptr++='"';
		ptr = cpw( ptr, base + entries[i].pos, entries[i].keylen );
		*ptr++='"';
		*ptr++='=';
		*ptr++='>';
		if ( entries[i].valisnull ) {
			*ptr++='N';
			*ptr++='U';
			*ptr++='L';
			*ptr++='L';
		} else {
			*ptr++='"';
			ptr = cpw( ptr, base + entries[i].pos + entries[i].keylen, entries[i].vallen );
			*ptr++='"';
		}

		if ( i+1 != in->size ) {
			*ptr++=',';
			*ptr++=' ';
		}
	}
	*ptr='\0';

	PG_FREE_IF_COPY(in,0);
	PG_RETURN_CSTRING(out);
}
