/*
 *
 * Copyright 2023 Oleg Borodin  <borodin@unix7.org>
 *
 */

#include <string.h>
#include <stdio.h>

#include <cllexer.h>

#define LTYPE_LETTER    1
#define LTYPE_PREFIX    2
#define LTYPE_DELIM     3
#define LTYPE_EOF       4

#define LCONTEXT_START  1
#define LCONTEXT_WORD   2
#define LCONTEXT_DELIM  3
#define LCONTEXT_PREFIX 4
#define LCONTEXT_ENDFL  5
#define LCONTEXT_UNDEF  7


static int get_ltype(char newletter) {
        switch (newletter) {
        case '-':
        case '+':
                return LTYPE_PREFIX;
        case '=':
                return LTYPE_DELIM;
        case EOF:
                return LTYPE_EOF;
        }
        return LTYPE_LETTER;
}

void cllexer_init(cllexer_t * lexer, char* arg) {
        lexer->arg = arg;
        lexer->rpos = 0;
        lexer->tpos = 0;
        lexer->currcontext = LCONTEXT_START;
        lexer->newletter = '\0';
}

static void cllexer_getletter(cllexer_t * lexer, char* arg, int size) {
        lexer->newletter = EOF;
        if (lexer->rpos < size) {
                lexer->newletter = arg[lexer->rpos++];
        }
}

int cllexer_gettok(cllexer_t * lexer, char* token) {

        char* arg = lexer->arg;
        size_t size = strlen(arg);

        if (lexer->currcontext == LCONTEXT_START) {
                lexer->newletter = arg[lexer->rpos++];
                int ltype = get_ltype(lexer->newletter);
                int newcontext = LCONTEXT_ENDFL;

                switch (ltype) {
                case LTYPE_PREFIX:{
                            newcontext = LCONTEXT_PREFIX;
                            break;
                    }
                case LTYPE_DELIM:{
                            newcontext = LCONTEXT_DELIM;
                            break;
                    }
                case LTYPE_LETTER:{
                            newcontext = LCONTEXT_WORD;
                            break;
                    }
                case LTYPE_EOF:{
                            newcontext = LCONTEXT_ENDFL;
                            break;
                    }
                }
                lexer->currcontext = newcontext;
        }

        while (lexer->currcontext != LCONTEXT_ENDFL) {

                int ltype = get_ltype(lexer->newletter);

                switch (lexer->currcontext) {
                case LCONTEXT_ENDFL:{
                            lexer->currcontext = LCONTEXT_ENDFL;
                            break;
                    }
                case LCONTEXT_DELIM:{
                            int newcontext = lexer->currcontext;

                            switch (ltype) {
                            case LTYPE_PREFIX:
                            case LTYPE_LETTER:{
                                        newcontext = LCONTEXT_WORD;
                                        break;
                                }
                            case LTYPE_EOF:{
                                        newcontext = LCONTEXT_ENDFL;
                                        break;
                                }
                            }
                            if (newcontext != lexer->currcontext) {
                                    lexer->currcontext = newcontext;
                                    token[lexer->tpos] = '\0';
                                    lexer->tpos = 0;
                                    return TOKEN_DELIM;
                            }
                            break;
                    }
                case LCONTEXT_PREFIX:{
                            int newcontext = lexer->currcontext;

                            switch (ltype) {
                            case LTYPE_DELIM:{
                                        newcontext = LCONTEXT_DELIM;
                                        break;
                                }
                            case LTYPE_LETTER:{
                                        newcontext = LCONTEXT_WORD;
                                        break;
                                }
                            case LTYPE_EOF:{
                                        newcontext = LCONTEXT_ENDFL;
                                        break;
                                }
                            }
                            if (newcontext != lexer->currcontext) {
                                    lexer->currcontext = newcontext;
                                    token[lexer->tpos++] = '\0';
                                    lexer->tpos = 0;
                                    return TOKEN_PREF;
                            }
                            break;
                    }
                case LCONTEXT_WORD:{
                            int newcontext = lexer->currcontext;

                            switch (ltype) {
                            case LTYPE_DELIM:{
                                        newcontext = LCONTEXT_DELIM;
                                        break;
                                }
                            case LTYPE_EOF:{
                                        newcontext = LCONTEXT_ENDFL;
                                        break;
                                }
                            }
                            if (newcontext != lexer->currcontext) {
                                    lexer->currcontext = newcontext;
                                    token[lexer->tpos] = '\0';
                                    lexer->tpos = 0;
                                    return TOKEN_WORD;
                            }
                            break;
                    }
                }
                token[lexer->tpos++] = lexer->newletter;
                cllexer_getletter(lexer, arg, size);
        }

        lexer->currcontext = LCONTEXT_ENDFL;
        lexer->tpos = 0;
        token[lexer->tpos] = '\0';
        strcpy(token, "EOF");
        return TOKEN_ENDF;
}