Cs1.c

#include "header.h"

//extern int pipe exists, so maybe we can do >, | and ;

void init_buffer()
{
    Terminal_Buffer = malloc(sizeof(char*) * capcity);
    for(int i=0;i<capcity;i++)Terminal_Buffer[i]=NULL;
    size_BUFER=0;
    return;
}

char** split(char* line)
{
    char** args = malloc(130 * sizeof(char*));
    int position = 0,size=130;
    char* x = strtok(line,sprtr);
    while(x)
    {
        if(position == size-1)
        {
            args = realloc(args,2*size*sizeof(char*));
            size=2*size;
        }
        args[position++]=x;
        x=strtok(NULL,sprtr);
    }
    args[position]=NULL;//to terminate the while loop in freeing args
    return args;
}

char* relpath_calc(char* abs_a,char* abs_b)
{
    char* str = malloc(4096);
    int count = 1;
    str[0]='.';
    char *a=abs_a,*b=abs_b;
    while(*a && *b && *a ==*b)
    {
        a++;
        b++;
    }
    //backtrack for (./a/bc ./a/b) to get (/bc /b) instead of (c NULL)
    if(!a && !b)return NULL;
    while(*(a)!='/' && *(b)!='/'){a--;b--;}
    while(*a)
    {
        if(*a=='/')
        {
            str[count++]='/';
            str[count++]='.';
            str[count++]='.';
        }
        a++;
    }
    while(*b)
    {
        str[count++]=*(b++);
    }
    return str;
}

bool cd(char* args)
{
    bool status = 0;
    if(!args || args[0]=='~')
    {
        free(OLD_DIR);
        OLD_DIR=getcwd(NULL,0);
        status = (cd(STARTING_DIR)==0);
    }
    else if(args[0]=='-')
    {
        char* x = getcwd(NULL,0);
        status = (chdir(OLD_DIR)==0);
        free(OLD_DIR);
        OLD_DIR=x;
    }
    else if(args[0]=='/')
    {
        free(OLD_DIR);
        OLD_DIR=getcwd(NULL,0);
        status = (chdir(args)==0);
        if(status==0)printf("Directory doesn't exist\n");
    }
    else if(strncmp(args,"./",2)==0)
    {
        free(OLD_DIR);
        OLD_DIR=getcwd(NULL,0);
        status = (chdir(args)==0);
        if(status==0)printf("No such directory exists\n");
    }
    if(status)
    {
        if(RELP_DIR)free(RELP_DIR);
        RELP_DIR = relpath_calc(STARTING_DIR,getcwd(NULL,0));
    }
    return status;
}

bool run(char** args)
{
    bool status = 0;
    int len = strlen(args[0]);
    if(strncmp(args[0],"exit",4)==0)
    {
        int x=0;
        if(args[2])printf("User has chosen to exit, we will ingone all further flags / following commands\n");
        args[0]+=4;
        if(args[0][0]!='(')exit(atoi(args[1]));
        else args[0]++;
        args[0][strlen(args[0]) - 1]='\0';
        if(args[0])x = atoi(args[0]);
        exit(x);
    }
    else if(len == 5 && strncmp(args[0],"clear",5)==0)
    {
        if(args[1])
        {
            printf("This command doesn't support flags/arguments\nskipping the rest\n");
            sleep(1);
        }
        printf("\033[H\033[J");
        printf("%s",LINUX);
        status=1;    

    }
    else if(len == 4 && strncmp(args[0],"echo",4)==0)
    {
        if(!args[1])
        {
            printf("USAGE: echo x prints x where x is single line string");
            return 0;
        }
        for(int i=1; args[i]; i++)
        {
            printf("%s ",args[i]);
        }
        printf("\n");
        status=1;
    }
    else if(len == 4 && strncmp(args[0],"help",4)==0 && strlen(args[0])==4)
    {
        printf(CYN"Welcome to the CzShell.\nCongratulations for making it this far."
                "\n\nList of commands with their description is as follows:\n\n"RST);
        printf("%s",docstrin);
        printf("press any key to return\n");
        char c;
        if(c = fgetc(stdin))return 1;
    }
    else if(len == 3 && strncmp(args[0],"pwd",3)==0 )
    {
        if(args[1])printf(RD"WARNING:  "RST"Chosen command doesn't support arguments/flags\nIgnoring "CYN"%s"RST" and onwards\n",args[1]);
        printf("%s\n",getcwd(NULL,0));
        status=1;
    }
    else if(len == 2 && strncmp(args[0],"cd",2)==0)
    {
        status = cd(args[1]);
    }
    else if(len == 2 && strncmp(args[0],"ls",2)==0)
    {
        if(args[1]==NULL)
        {
            DIR* x = opendir(".");
            if(!x)return 0;
            printf("listing out Directory: %s\n",OLD_DIR?OLD_DIR:STARTING_DIR);
            printf("Name\n");
            struct dirent* f=NULL;
            while(f=readdir(x))
            {
                printf("%s\n",f->d_name);
            }
            closedir(x);
            printf("\n\n");
            status = 1;
        }
        else if(args[1][0] != '-')
        {
            DIR* x = opendir(args[1]);
            if(!x)return 0;
            printf("listing out Directory: %s\n",OLD_DIR?OLD_DIR:STARTING_DIR);
            printf("Name\n");
            struct dirent* f=NULL;
            while(f=readdir(x))
            {
                printf("%s\n",f->d_name);
            }
            closedir(x);
            printf("\n\n");
            status = 1;
        }
        else status = 0;
    }
    else if(len == 3 && strncmp(args[0],"cat",3)==0)
    {
        if(!args[1])printf("USAGE : cat filepath, prints contents of file(if not binary)\n");
        else
        {
            FILE* f = fopen(args[1],"r");
            if(!f)perror("Error while opening file");
            else
            {
                int c;
                c = fgetc(f);
                if (!isprint(c) && !isspace(c) && c != EOF)
                {
                    printf("This looks like a binary file.\npress 'Y' (case sensitive) if you want to print regardless");
                    if(getc(stdin)!='Y')
                    {
                        ungetc(c,f);
                        fclose(f);
                        return 0;
                    }
                }
                ungetc(c,f);
                while((c=fgetc(f))!=-1)printf("%c",c);
                fclose(f);
            }
        }
    }
    else if(len == 5 && strncmp(args[0],"touch",5)==0)
    {
        FILE* f = fopen(args[1],"a");
        if(!f)perror("Error while opening file");
        else fclose(f);
    }
    else
    {
        printf("It seems you have entered an invalid command.\nPlease try calling help for a list of possible commands\n");
    }
    return status;
}

bool parse()
{
    char* line = Terminal_Buffer[(size_BUFER == 0) ? (capcity - 1) : (size_BUFER - 1)];
    char** args = split(line);
    bool s = run(args);
    free(args);
    return s;
}

bool input()
{
    char* s = malloc(4196*sizeof(char));
    char c;
    int position=0,iter=1;
    while((c = fgetc(stdin)))
    {
        if(c<0)return position>0;
        if(c == '\n' )
        {
            s[position]=' ';
            s[position+1]='\0';
            break;
        }
        else if (c==-1)break;
        if(position>=4192 * iter)
        {
            iter++;
            s = realloc(s,sizeof(char)*4192 * iter + 4);
        }
        s[position++]=c;
    }
    if(Terminal_Buffer[size_BUFER])free(Terminal_Buffer[size_BUFER]);
    Terminal_Buffer[size_BUFER++]=s;
    size_BUFER=size_BUFER%capcity;
    return 1;
}

void term(void)
{
    printf("exiting in \0337");
    fflush(stdout);
    for(int i=0;i<3;i++)
    {
        printf("\0338\0337%d seconds",3-i);
        fflush(stdout);
        sleep(1);
    }
    printf("\r\x1B[2K");
    return;
}

int main()
{
    atexit(term);
    init_buffer();
    STARTING_DIR=getcwd(NULL,0);
    OLD_DIR=NULL;
    printf("%s",LINUX);
    bool SUCCEEDED = 1;
    while(1)
    {
        printf("%s%s>%s", (SUCCEEDED? GREN:RD), (RELP_DIR==NULL?"":RELP_DIR), RST);
        if(input())SUCCEEDED = parse();
        // sleep(1);
    }
    return 0;
}