#include "../includes/scanner.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

const char* SourceCode;
int Position = 0;
int SourceLength = 0;
int ScannerAtEnd(void);
char PeekScanner(void);
char AdvanceScanner(void);
Token* ParseString(void);
Token* ParseDirective(void);
Token* ParseIdentifier(void);

List* GenerateTokenList(const char* source) {
    List* tokens = CreateList();
    Token* token = NULL;

    if (!tokens) return NULL;

    SourceCode = source;
    SourceLength = strlen(source);

    for(int i = 0; i < SourceLength; i++) {
        char c = AdvanceScanner();
        switch(c) {
            case ' ':
            case '\r':
            case '\t':
                break; //Ignore whitespace
            case ';':
                while(!ScannerAtEnd() && PeekScanner() != '\n') AdvanceScanner();

                break;
            case '.': //directive like ".org" or ".db"
                token = ParseDirective();
                if (token) AddListItem(token, sizeof(Token), tokens);
                break;
            case '"':
                token = ParseString();
                if (token) AddListItem(token, sizeof(Token), tokens);
                break;
            case ',':
                AddListItem(CreateToken(COMMA, ","), sizeof(Token), tokens);
                break;
            default:
                // if (c >= '0' && c <= '9') {
                //     //Number

                //     break;
                // }

                token = ParseIdentifier();

                if (token) AddListItem(token, sizeof(Token), tokens);

                break;
        }

        token = NULL;
    }

    return tokens;
}

Token* ParseDirective(void) {
    char directive[10] = { 0 };
    int length = 0;

    for(; length < sizeof directive - 1; length++) {
        if (PeekScanner() == ' ') break;

        directive[length] = AdvanceScanner();
    }

    if (strcmp(directive, ".db") == 0) {
        return CreateToken(DB, ".db");
    } else if (strcmp(directive, ".org") == 0) {
        //fprintf(stderr, "[Warning] Org is not a supported directive.\n");
        return NULL;
    }

    fprintf(stderr, "[Error] Unknown assembler directive '%s'\n", directive);
    //Ignore the line 
    while(PeekScanner() != '\n') AdvanceScanner();

    return NULL;
}

Token* ParseString(void) {
    int start = Position;

    while(!ScannerAtEnd() && PeekScanner() != '"') {
        AdvanceScanner();
    }

    char* lexeme = calloc(Position - start, sizeof(char));
    memccpy(lexeme, &SourceCode[start], sizeof(char), Position - start);

    AdvanceScanner();

    Token* token = CreateToken(STRING, lexeme);

    return token;
}

Token* ParseIdentifier(void) {
    int start = Position;

    while(!ScannerAtEnd() && PeekScanner() != ' ' && PeekScanner() != '\n') {
        AdvanceScanner();
    }

    if (Position - start == 0) return NULL;
    
    char* lexeme = calloc(Position - start, sizeof(char));
    memccpy(lexeme, &SourceCode[start], sizeof(char), Position - start);

    return CreateToken(IDENTIFIER, lexeme);
}

char PeekScanner(void) {
    if (Position > SourceLength) return '\0';

    return SourceCode[Position];
}

char AdvanceScanner(void) {
    if (ScannerAtEnd()) return '\0';

    return SourceCode[Position++];
}

int ScannerAtEnd(void) {
    return Position >= SourceLength;
}