%{
#include <stdio.h>
#include <string.h>
#include "y.tab.h"

/* Buffer for building field content */
static char field_buffer[8192];
static int field_pos = 0;

void reset_field_buffer() {
    field_pos = 0;
    field_buffer[0] = '\0';
}

void append_to_field(char c) {
    if (field_pos < sizeof(field_buffer) - 1) {  /* Reserve space for null terminator */
        field_buffer[field_pos++] = c;
        field_buffer[field_pos] = '\0';
    }
}

void append_string_to_field(const char* s) {
    while (*s && field_pos < sizeof(field_buffer) - 1) {  /* Reserve space for null terminator */
        field_buffer[field_pos++] = *s++;
    }
    field_buffer[field_pos] = '\0';
}

char* get_field_content() {
    char* result = strdup(field_buffer);  /* NOTE: Caller must free() this memory */
    if (!result) {
        fprintf(stderr, "Memory allocation failed in get_field_content()\n");
        exit(1);  /* Conservative approach: exit on memory failure */
    }
    return result;
}
%}

%option noyywrap
%option yylineno

%x ESCAPED_FIELD

TEXTDATA    [\x20-\x21\x23-\x2B\x2D-\x7E]
COMMA       \x2C
CR          \x0D
LF          \x0A
DQUOTE      \x22
CRLF        {CR}{LF}

%%

{COMMA}                 { return COMMA_TOK; }

{CRLF}                  { return CRLF_TOK; }

{LF}                    { return CRLF_TOK; }

{DQUOTE}                { 
                          reset_field_buffer(); 
                          BEGIN(ESCAPED_FIELD); 
                        }

<ESCAPED_FIELD>{DQUOTE}{DQUOTE}  { append_to_field('"'); }

<ESCAPED_FIELD>{DQUOTE}          { 
                                   yylval.str = get_field_content();
                                   BEGIN(INITIAL);
                                   return FIELD_TOK;
                                 }

<ESCAPED_FIELD>{TEXTDATA}        { append_to_field(yytext[0]); }

<ESCAPED_FIELD>{COMMA}           { append_to_field(','); }

<ESCAPED_FIELD>{CR}              { append_to_field('\r'); }

<ESCAPED_FIELD>{LF}              { append_to_field('\n'); }

<ESCAPED_FIELD>.                 { append_to_field(yytext[0]); }

<ESCAPED_FIELD><<EOF>>           {
                                   /* Handle unterminated quoted field */
                                   yylval.str = get_field_content();
                                   BEGIN(INITIAL);
                                   return FIELD_TOK;
                                 }

{TEXTDATA}+             { 
                          yylval.str = strdup(yytext);  /* NOTE: Caller must free() this memory */
                          if (!yylval.str) {
                              fprintf(stderr, "Memory allocation failed in TEXTDATA rule\n");
                              exit(1);  /* Conservative approach: exit on memory failure */
                          }
                          return FIELD_TOK; 
                        }

[ \t]                   { /* ignore whitespace outside of fields */ }

.                       { return yytext[0]; }

%%