/* Filename: scanner.c
   PURPOSE:
 * SCANNER.C: Functions implementing a Lexical Analyzer (Scanner)
 * as required for CST8152, Assignment #2
 * scanner_init() must be called before using the scanner.
 * The file is incomplete;
 * Author: Victor Fernandes, 040772243
 * Provided by: Svillen Ranev
 * Version: 1.17.1
 * Date: 30 January 2017
 * Function list: scanner_init, malar_next_token, get_next_state, char_class,
  aa_func02, aa_func03, aa_func05, aa_func08, aa_func10, aa_func12 aa_func13, atool, iskeyword
 */

 /* The #define _CRT_SECURE_NO_WARNINGS should be used in MS Visual Studio projects
  * to suppress the warnings about using "unsafe" functions like fopen()
  * and standard sting library functions defined in string.h.
  * The define does not have any effect in Borland compiler projects.
  */
#define _CRT_SECURE_NO_WARNINGS

#include <stdio.h>   /* standard input / output */
#include <ctype.h>   /* conversion functions */
#include <stdlib.h>  /* standard library functions and constants */
#include <string.h>  /* string functions */
#include <limits.h>  /* integer types constants */
#include <float.h>   /* floating-point types constants */

  /*#define NDEBUG        to suppress assert() call */
#include <assert.h>  /* assert() prototype */

/* project header files */
#include "buffer.h"
#include "token.h"
#include "table.h"
#include "stable.h"

#define DEBUG  /* for conditional processing */
#undef  DEBUG



/* Global objects - variables */
/* This buffer is used as a repository for string literals.
   It is defined in platy_st.c */
extern Buffer * str_LTBL; /*String literal table */
int line;                 /* current line number of the source code */
extern int scerrnum;      /* defined in platy_st.c - run-time error number */
extern STD sym_table;     /* symbol table */
/* Local(file) global objects - variables */
static Buffer *lex_buf;   /*pointer to temporary lexeme buffer*/

/* No other global variable declarations/definitiond are allowed */

/* scanner.c static(local) function  prototypes */
static int char_class(char c);               /* character class function */
static int get_next_state(int, char, int *); /* state machine function */
static int iskeyword(char * kw_lexeme);      /*keywords lookup functuion */
static long atool(char * lexeme);            /* converts octal string to decimal value */

/* Prepares the Scanner to read the source code buffer
 * Author: Svillen Ranev
 * Called functions: b_isempty, b_setmark, b_retract_to_mark, b_reset
 * Parameters:
 *	- pBuffer sc_buf
 * Return values:
 *  - 1 (failure), 0 (success)
*/
int scanner_init(Buffer * sc_buf) {
	if (b_isempty(sc_buf)) return EXIT_FAILURE;/*1*/
	/* in case the buffer has been read previously  */
	b_setmark(sc_buf, 0);
	b_retract_to_mark(sc_buf);
	b_reset(str_LTBL);
	line = 1;
	return EXIT_SUCCESS;/*0*/
/*   scerrnum = 0;  *//*no need - global ANSI C */
}
/* Reads the source code buffer and generates a token
 * Author: Victor Fernandes
 * Version: 0.0.1
 * Called functions: aa_table[], b_getc, b_setmark, b_getcoffset, b_retract_to_mark,
 b_retract, b_mark, b_eob, b_create, b_addc, b_free, isalpha, isalnum, get_next_state
 * Parameters:
  - pBuffer sc_buf
 * Return values: Token
 * Algorithm:
   Read a character from the source buffer, one by one, and match string patterns to tokens.
   If an illegal sequence is found while starting a pattern off of the first matching character,
   it returns a token with an error code with the infringing character. If the scanner matches
   a valid pattern it returns a Token with the appropriate code.
*/
Token malar_next_token(Buffer * sc_buf)
{
	Token t;           /* token to return after recognition */
	unsigned char c;   /* input symbol */
	int state = 0;     /* initial state of the FSM */
	short lexstart;    /* start offset of a lexeme in the input buffer */
	short lexend;      /* end offset of a lexeme in the input buffer */
	int accept = NOAS; /* type of state - initially not accepting */

	/* Counter for loops in string error case */
	int i;
	/*String offset for the str_LTBL*/
	static short str_offset = 0;
	/* temporary buffer used to store an erroneous string literal*/
	pBuffer err_lex_buf;

	if (sc_buf == NULL) {
		scerrnum = 1;
		return aa_table[ES]("RUN TIME ERROR: "); /* WHOOPS */
	}

	while (1) { /* endless loop broken by token returns; it will generate a warning */

		/* Get symbol from buffer */
		c = b_getc(sc_buf);

		switch (c) {
		case 255: t.code = SEOF_T; return t; /* EOF */
		case '\0': t.code = SEOF_T; return t; /* Source EOF */
		case '\n': line++; continue; /* Ignore new line, increment line count */
		case '\r': line++; continue; /* CR, increment line count*/
		case ' ': continue; /* Ignore white space */
		case '\t': continue; /* Ignore tabs */
		case ';': t.code = EOS_T; return t; /* End of statement */
		case ',': t.code = COM_T; return t; /* Comma */
		case '{': t.code = LBR_T; return t; /* Left brace */
		case '}': t.code = RBR_T; return t; /* Right brace */
		case '(': t.code = LPR_T; return t; /* Left parenthesis */
		case ')': t.code = RPR_T; return t; /* Right parenthesis */
		case '+': t.code = ART_OP_T; t.attribute.arr_op = PLUS; return t; /* Addition operator */
		case '-': t.code = ART_OP_T; t.attribute.arr_op = MINUS; return t; /* Substraction operator */
		case '*': t.code = ART_OP_T; t.attribute.arr_op = MULT; return t; /* Multiplication operator */
		case '/': t.code = ART_OP_T; t.attribute.arr_op = DIV; return t; /* Devision operator */
		case '>': t.code = REL_OP_T; t.attribute.rel_op = GT; return t; /* Greater-than relational operator */
		case '<':
			c = b_getc(sc_buf);
			if (c == '>') {
				t.code = REL_OP_T;
				t.attribute.rel_op = NE; /* Negation operator */
				return t;
			}
			else if (c == '<') {
				t.code = SCC_OP_T; /* String concatenation operator */
				return t;
			}
			else {
				t.code = REL_OP_T;
				t.attribute.rel_op = LT; /* Less-than operator */
				b_retract(sc_buf);
				return t;
			}

		case '.':
			b_setmark(sc_buf, b_getcoffset(sc_buf)); /* Set mark before continuing (AND|OR case) */
			c = b_getc(sc_buf);
			if (c == 'A' && b_getc(sc_buf) == 'N' && b_getc(sc_buf) == 'D' && b_getc(sc_buf) == '.') {
				t.code = LOG_OP_T;
				t.attribute.log_op = AND;
				return t;
			}
			else if (c == 'O' && b_getc(sc_buf) == 'R' && b_getc(sc_buf) == '.') {
				t.code = LOG_OP_T;
				t.attribute.log_op = OR;
				return t;
			}
			t.code = ERR_T; /* "That character's not supposed to be here" case */
			t.attribute.err_lex[0] = '.';
			t.attribute.err_lex[1] = '\0';
			b_retract_to_mark(sc_buf);
			return t;
		case '!':
			c = b_getc(sc_buf);
			if (c == '<') { /* It's a comment line */
				/* Consume chars until line ends */
				for (; c != '\0' && c != '\r' && c != '\n' && c != 255; c = b_getc(sc_buf));
				++line;
				continue;
			}
			else { /* Bad character, pump out an error token */
				t.code = ERR_T;
				b_retract(sc_buf);
				b_retract(sc_buf); /* Retract twice to re-read '!' */
				t.attribute.err_lex[0] = c = b_getc(sc_buf);
				t.attribute.err_lex[1] = c = b_getc(sc_buf);
				t.attribute.err_lex[2] = '\0';
				/* Consume the rest of the caracters to ignore the line*/
				for (; c != '\0' && c != '\r' && c != '\n' && c != 255; c = b_getc(sc_buf));
				++line;
				return t;
			}
		case '=':
			c = b_getc(sc_buf);
			if (c == '=') { /* Relational equals-to operator */
				t.code = REL_OP_T;
				t.attribute.rel_op = EQ;
				return t;
			}
			b_retract(sc_buf);
			t.code = ASS_OP_T; /* Assignment operator */
			return t;
		case '\"': /* Don't quote me on this */

			/* Track the beginning of string */
			b_setmark(sc_buf, b_getcoffset(sc_buf));
			lexstart = b_mark(sc_buf);
			lexend = lexstart;
			c = b_getc(sc_buf);
			/* Step through the string literal and track progress  */
			for (; c != '\"'; c = b_getc(sc_buf), ++lexend) {
				if (c == '\n' || c == '\r')
					++line;
				if (c == '\0' || c == 255) { /* Illegal string, make it an error token */
					b_retract_to_mark(sc_buf);
					b_retract(sc_buf); /* Retract one more time to re-read '"' into err_lex */
					t.code = ERR_T;

					err_lex_buf = b_create(100, 10, 'a'); /* Start up temporary buffer */

					c = b_getc(sc_buf);
					for (i = 0; i < (lexend - lexstart); c = b_getc(sc_buf), ++i) {
						/* Continue until the end of the lexeme where error was found */
						if (i < (ERR_LEN) || c != 255 || c != '\0')
							b_addc(err_lex_buf, c);
					}
					/* Pass the complete erroneous string to error state accepting function*/
					t = aa_table[ES](b_setmark(err_lex_buf, 0));
					b_free(err_lex_buf); /* Clean up the temporary buffer */
					return t;
				}
			} /* end for loop, string finished and considered valid */
			b_retract_to_mark(sc_buf);

			/* Copy the matched string literal to str_LTBL */
			t.attribute.str_offset = str_offset;
			c = b_getc(sc_buf);
			for (; lexstart < lexend; c = b_getc(sc_buf), ++lexstart, ++str_offset) {
				b_addc(str_LTBL, c);
			}
			b_addc(str_LTBL, '\0'); ++str_offset; t.code = STR_T;
			return t;

		default:
			if (isalpha(c) || isalnum(c)) {

				/*Set mark to beginning of lexeme*/
				b_retract(sc_buf);
				b_setmark(sc_buf, b_getcoffset(sc_buf));
				lexstart = b_mark(sc_buf);
				lexend = lexstart;
				state = 0;

				while (accept == NOAS) {
					state = get_next_state(state, b_getc(sc_buf), &accept);
					if (accept != NOAS) { break; }
				}

				/*
				 * Entering Accepting State
				 */

				if (as_table[state] == ASWR) { b_retract(sc_buf); }

				/* Get end of lexeme */
				lexend = b_getcoffset(sc_buf);

				b_retract_to_mark(sc_buf);

				lex_buf = b_create(1, 1, 'a');

				/* Copy the scanned lexeme into lexical buffer */
				for (; lexstart < lexend; ++lexstart) {
					b_addc(lex_buf, b_getc(sc_buf));
				}
				b_addc(lex_buf, '\0');

				if (aa_table[state] != NULL) {
					t = aa_table[state](b_setmark(lex_buf, 0));
				}
				else {
					scerrnum = 1;
					t = aa_table[ES]("RUN TIME ERROR: ");
					return t;
				}
				b_free(lex_buf);
			}

			/* Invalid character */
			else {
				t.code = ERR_T;
				t.attribute.err_lex[0] = c;
				t.attribute.err_lex[1] = '\0';
			}
			return t;
		}



	} /*end while(1)*/
}

/* Looks up the transition table for the next state given the input character
   Author: Victor Fernandes
   Version: 0.0.1
   Called functions: char_class, assert, printf, as_table
   Parameters:
	- int state: the starting point for the transition table lookup
	- char c: the input character for table lookup
	- int *accept: pointer to the accepting state of the scanner
   Return values: int (the next state value of the scanner)
*/
int get_next_state(int state, char c, int *accept)
{
	int col;
	int next;
	col = char_class(c);
	next = st_table[state][col];
#ifdef DEBUG
	printf("Input symbol: %c Row: %d Column: %d Next: %d \n", c, state, col, next);
#endif

	assert(next != IS);

#ifdef DEBUG
	if (next == IS) {
		printf("Scanner Error: Illegal state:\n");
		printf("Input symbol: %c Row: %d Column: %d\n", c, state, col);
		exit(1);
	}
#endif
	*accept = as_table[next];
	return next;
}

/* Matches the column value in the transition table to the given input character
   Author: Victor Fernandes
   Version: 0.0.1
   Called functions: N/A
   Parameters:
	- char c: the input character to be matched in the transition table
   Return values: int (the value representing the column in the transition table)
*/
int char_class(char c)
{
	int val;

	if (isalpha(c))
		val = 0;
	else if (c == '0')
		val = 1;
	else if (c > '0' && c < '8')
		val = 2;
	else if (c == '8' || c == '9')
		val = 3;
	else if (c == '.')
		val = 4;
	else if (c == '#')
		val = 5;
	else
		val = 6;

	return val;
}

/* Generates a token for an arithmetic variable identifer or keyword
   Author: Victor Fernandes
   Version: 0.0.1
   Called functions: iskeyword, calloc, aa_table[], strlen, strncpy, free
   Parameters:
	- char* lexeme: the string pattern matched by the FA
   Return values: Token
*/
Token aa_func02(char lexeme[]) {
	unsigned kw_idx, offset; /* Variable to contain keyword table index */
	Token t;
	char v_type;
	char* temp_str;

#ifdef DEBUG
	printf("Lexeme: '%s'\n", lexeme);
#endif

	kw_idx = iskeyword(lexeme);
	if (kw_idx != -1) { /* Keyword check */
		t.code = KW_T;
		t.attribute.kwt_idx = kw_idx;
		return t;
	}

	/* Not a keyword? Must be AVID*/
	t.code = AVID_T;
	if ((temp_str = (char*)calloc(VID_LEN + 1, sizeof(char))) == NULL) {
		return aa_table[ES]("RUN TIME ERROR: ");
	}

	strncpy(temp_str, lexeme, VID_LEN);

	switch (lexeme[0]) { /* Read first character of lexeme for implicit type (not used yet?)*/
	case 'i':
	case 'o':
	case 'd':
	case 'n':
		/* Integer */
		v_type = 'I';
		break;
	default:
		/* Floating point*/
		v_type = 'F';
		break;
	}
	if ((offset = st_install(sym_table, temp_str, v_type, line)) == -1){
		printf("Error: Install failed - Symbol Table is full.\n");
		st_store(sym_table);
		free(temp_str);
		exit(1);
	}
	t.attribute.vid_offset = offset;
	free(temp_str);

	return t;
}

/* Generates a token for an string variable identifer
   Author: Victor Fernandes
   Version: 0.0.1
   Called functions: calloc, aa_table[], strlen, strncpy, free
   Parameters:
	- char* lexeme: the string pattern matched by the FA
   Return values: Token
*/
Token aa_func03(char lexeme[]) {
	Token t;
	unsigned offset;
	char* temp_str;
	if ((temp_str = (char*)calloc(VID_LEN + 2, sizeof(char))) == NULL) {
		return aa_table[ES]("RUN TIME ERROR: ");
	}

	strncpy(temp_str, lexeme, VID_LEN);
	temp_str[strlen(temp_str) - 1] = '#'; /* Add# to end of the SVID */
	
	if ((offset = st_install(sym_table, temp_str, 'S', line)) == -1){
		printf("Error: Install failed - Symbol Table is full.\n");
		st_store(sym_table);
		free(temp_str);
		exit(1);
	}
	t.code = SVID_T;
	t.attribute.vid_offset = offset;
	free(temp_str);

	return t;
}

/* Generates a token for a decimal integer literal constant (DIL)
   Author: Victor Fernandes
   Version: 0.0.1
   Called functions: atol, aa_table[]
   Parameters:
	- char* lexeme: the string pattern matched by the FA
   Return values: Token
*/
Token aa_func05(char lexeme[]) {
	Token t;
	long temp_num;

	temp_num = atol(lexeme);
	/* MOVE TO DEFINE */
	if (temp_num > 32767 || temp_num < 0) { /* Overflow error */
		t = aa_table[ES](lexeme);
		return t;
	}
	t.code = INL_T;
	t.attribute.int_value = (int)temp_num;
	return t;
}

/* Generates a token for a floating-point literal
   Author: Victor Fernandes
   Version: 0.0.1
   Called functions: strtof, aa_table[]
   Parameters:
	- char* lexeme: the string pattern matched by the FA
   Return values: Token
*/
Token aa_func08(char lexeme[]) {
	Token t;
	double temp_dbl = 0.0;
	temp_dbl = atof(lexeme);


	if ((temp_dbl > FLT_MAX) || ((temp_dbl != 0.0) && (temp_dbl < FLT_MIN))) { /* Overflow error */
		return aa_table[ES](lexeme);
	}

	t.code = FPL_T;
	t.attribute.flt_value = (float)temp_dbl;
	return t;
}

/* Generates a token for an octal integer literal
   Author: Victor Fernandes
   Version: 0.0.1
   Called functions: strlen, aa_table[], atool
   Parameters:
	- char* lexeme: the string pattern matched by the FA
   Return values: Token
*/
Token aa_func10(char lexeme[]) {
	Token t;
	long new_olval;

	if (strlen(lexeme) > INL_LEN + 1) {
		t = aa_table[ES](lexeme);
	}

	t.code = INL_T;
	new_olval = atool(lexeme);

	if (new_olval < 0 || new_olval > PLT_SHRT_MAX) {
		t = aa_table[ES](lexeme);
		return t;
	}

	t.code = INL_T;
	t.attribute.int_value = (int)new_olval;

	return t;
}

/* Generates a token for a general error token
   Author: Victor Fernandes
   Version: 0.0.1
   Called functions: aa_table[]
   Parameters:
	- char* lexeme: the string pattern matched by the FA
   Return values: Token
*/
Token aa_func12(char lexeme[]) {

	/*
	This function does the same as aa_func13, except that it is marked as
	non-retracting in the accepting function state, but the token is generated
	exactly the same way
	*/
	return aa_table[ESWR](lexeme);
}

/* Generates a token for a general error token
   Author: Victor Fernandes
   Version: 0.0.1
   Called functions: strlen, aa_table[]
   Parameters:
	- char* lexeme: the string pattern matched by the FA
   Return values: Token
*/
Token aa_func13(char lexeme[]) {
	Token t;
	unsigned int i;
	t.code = ERR_T;
	for (i = 0; i < (ERR_LEN) && i < strlen(lexeme); i++)
		t.attribute.err_lex[i] = lexeme[i];

	if (strlen(lexeme) > ERR_LEN) {
		t.attribute.err_lex[i - 1] = '.';
		t.attribute.err_lex[i - 2] = '.';
		t.attribute.err_lex[i - 3] = '.';
	}
	t.attribute.err_lex[i] = '\0';

	return t;
}

/* Returns an octal representation of a string
   Author: Victor Fernandes
   Version: 0.0.1
   Called functions: N/A
   Parameters:
	- char* lexeme: the string pattern to convert
   Return values: long (integer representation of the octal string)
*/
long atool(char * lexeme) {
	int i, x = 1;
	long result = 0;

	for (i = strlen(lexeme); i > 0; i--, x *= 8)
		result += x*(lexeme[i - 1] - '0');
	return result;
}

/* Looks up the string pattern on the keyword table
   Author: Victor Fernandes
   Version: 0.0.1
   Called functions: N/A
   Parameters:
	- char* lexeme: the string pattern to look up in kw_table
   Return values: int -1 (could not find a match),
  int [1 - KW_SIZE] index location of the matching keyword
*/
int iskeyword(char * kw_lexeme) {
	int i;

	if (kw_lexeme == NULL) return -1;

	for (i = 0; i < KWT_SIZE; i++) {
		if (strcmp(kw_table[i], kw_lexeme) == 0) { return i; }
	}
	return -1;
}