90s/rush.c

#include <termios.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <linux/limits.h>
#include <time.h>
#include <stdbool.h>
#include <signal.h>

#include "color.h"
#include "constants.h"
#include "history.h"
#include "commands.h"

void quit_sig(int sig) {
    exit(0);
}

void change_terminal_attribute(int option) {  
    static struct termios oldt, newt;
    tcgetattr(STDIN_FILENO, &oldt);
    if (option) {
        newt = oldt;
        newt.c_lflag &= ~(ICANON | ECHO); // allows getchar without pressing enter key and echoing the character twice
        tcsetattr(STDIN_FILENO, TCSANOW, &newt); // set settings to stdin
    } else {
        tcsetattr(STDIN_FILENO, TCSANOW, &oldt); // restore to old settings
    }
}  

char **setup_path_variable() {
    char *envpath = getenv("PATH");
    if (envpath == NULL) {
        fprintf(stderr, "rush: PATH environment variable is missing\n");
        exit(EXIT_FAILURE);
    }
    char *path_cpy = malloc(sizeof(char) * (strlen(envpath) + 1));
    char *path = malloc(sizeof(char) * (strlen(envpath) + 1));
    if (path_cpy == NULL || path == NULL) {
        fprintf(stderr, "rush: Error allocating memory\n");
        exit(EXIT_FAILURE);
    }
    strcpy(path_cpy, envpath);
    strcpy(path, envpath);
    int path_count = 0;
    while (*path_cpy != '\0') {
        // count number of : to count number of elements
        if (*path_cpy == ':') {
            path_count++;
        }
        path_cpy++;
    }
    path_count += 2; // adding one to be correct and one for terminator
    char **paths = malloc(sizeof(char *) * path_count);
    if (paths == NULL) {
        fprintf(stderr, "rush: Error allocating memory\n");
        exit(EXIT_FAILURE);
    }
    char *token = strtok(path, ":");
    int counter = 0;
    while (token != NULL) {
        paths[counter] = token; // set element to the pointer of start of path
        token = strtok(NULL, ":");
        counter++;
    }
    paths[counter] = NULL;
    return paths;
}

bool find_command(char **paths, char *command) {
    if (strcmp(command, "") == 0) {
        return false;
    }
    while (*paths != NULL) {
        char current_path[PATH_MAX];
        current_path[0] = '\0';
        sprintf(current_path, "%s/%s", *paths, command);
        if (access(current_path, X_OK) == 0) {
            // command is executable
            return true;
        } else {
            if (is_builtin(command)) {
                return true;
            }
        }
        paths++;
    }
    return false;
}

void shiftleft(int chars) {
    printf("\033[%dD", chars);
}

void shiftright(int chars) {
    printf("\033[%dC", chars);
}

char *readline(char **paths) {
    int bufsize = RL_BUFSIZE;
    int position = 0;
    char *buffer = malloc(sizeof(char) * bufsize);

    bool moved = false;
    bool backspaced = false;
    bool navigated = false;
    bool insertatmiddle = false;
    if (!buffer) {
        fprintf(stderr, "rush: Error allocating memory\n");
        exit(EXIT_FAILURE);
    }

    buffer[0] = '\0';
    while (1) {
        int c = getchar(); // read a character
        int buf_len = strlen(buffer);
        
        // check each character user has input
        switch (c) {
            case EOF:
                exit(EXIT_SUCCESS);
            case 10: {
                // enter/new line feed
                if (buf_len == 0) {
                    break;
                }
                buffer[buf_len] = '\0';
                // clear all characters after the command
                for (int start = buf_len + 1; buffer[start] != '\0'; start++) {
                    buffer[start] = '\0';
                }
                printf("\n"); // give space for response
                save_command_history(buffer);
                position = 0;
                return buffer;
            }
            case 127: // backspace
                if (buf_len >= 1) {
                    position--;
                    for (int i = position; i < buf_len; i++) {
                        // shift the buffer
                        buffer[i] = buffer[i + 1];
                    }
                    backspaced = true;
                    moved = false;
                }
                break;
            case 27: // arrow keys comes at three characters, 27, 91, then 65-68
                if (getchar() == 91) {
                    int arrow_key = getchar();
                    if (arrow_key == 65) { // up
                        // read history file and fill prompt with latest command
                        char *last_command = read_command(1);
                        if (last_command != NULL) {
                            strcpy(buffer, last_command);
                            navigated = true;
                        }
                        moved = false;
                        break;
                    } else if (arrow_key == 66) { // down
                        char *last_command = read_command(0);
                        if (last_command != NULL) {
                            strcpy(buffer, last_command);
                            navigated = true;
                        }
                        moved = false;
                        break;
                    } else if (arrow_key == 67) { // right
                        if (position < buf_len) {
                            shiftright(1);
                            position++;
                        }
                        moved = true;
                        break;
                    } else if (arrow_key == 68) { // left
                        if (position >= 1) {
                            shiftleft(1);
                            position--;
                        }
                        moved = true;
                        break;
                    } 
                }
            default:
                if (c > 31 && c < 127) {
                    if (position == buf_len) {
                        // Append character to the end of the buffer
                        buffer[buf_len] = c;
                        buffer[buf_len + 1] = '\0';
                        moved = false;
                        navigated = false;
                    } else {
                        // Insert character at the current position
                        memmove(&buffer[position + 1], &buffer[position], buf_len - position + 1);
                        buffer[position] = c;
                        shiftright(1);
                        insertatmiddle = true;
                    }
                    position++;
                }
        }
        if (navigated && buf_len >= 1) {
            if (position != 0) {
                shiftleft(buf_len);  // move cursor to the beginning
                printf("\033[K"); // clear line to the right of cursor
            }
        }
        buf_len = strlen(buffer);
        if (moved) {
            moved = false;
            continue;
        }
        if (!navigated) {
            if (position != buf_len) {
                // not at normal place
                if (backspaced) {
                    shiftleft(position + 1);
                } else {
                    shiftleft(position);  // move cursor to the beginning
                }
            } else if (buf_len > 1) {
                if (backspaced) {
                    shiftleft(buf_len + 1);  // move cursor to the beginning
                } else {
                    shiftleft(buf_len - 1);  // move cursor to the beginning
                }
            } else if (buf_len == 1) {
                if (backspaced) {
                    shiftleft(2);
                }
            } else if (buf_len == 0) {
                if (backspaced) {
                    shiftleft(1);    
                }
            }
            printf("\033[K"); // clear line to the right of cursor
        } else {
            navigated = false;
        }
        char *cmd_part = strchr(buffer, ' ');
        char *command_without_arg = NULL;
        int cmd_len = 0;
        bool valid;

        if (cmd_part != NULL) {
            cmd_len = cmd_part - buffer;
            char *cmd = malloc(sizeof(char) * (cmd_len + 1));
            command_without_arg = malloc(sizeof(char) * (cmd_len + 1));
            if (cmd == NULL || command_without_arg == NULL) {
                fprintf(stderr, "rush: Error allocating memory\n");
                exit(EXIT_FAILURE);
            }
            for (int i = 0; i < (cmd_part - buffer); i++) {
                cmd[i] = buffer[i];
            }
            strcpy(command_without_arg, cmd);
            cmd[cmd_len] = '\0';
            command_without_arg[cmd_len] = '\0';
            valid = find_command(paths, cmd);
            free(cmd);
        } else {
            valid = find_command(paths, buffer);
        }

        if (valid) {
            if (command_without_arg != NULL) {
                buffer += cmd_len;
                printf("\x1b[38;2;137;180;250m%s\x1b[0m\x1b[38;2;255;255;255m%s\x1b[0m", command_without_arg, buffer); // print green as valid command, but only color the command, not the arguments
                buffer -= cmd_len;
            } else {
                printf("\x1b[38;2;137;180;250m%s\x1b[0m", buffer); // print green as valid command
            }
        } else {
            if (command_without_arg != NULL) {
                buffer += cmd_len;
                printf("\x1b[38;2;243;139;168m%s\x1b[0m\x1b[38;2;255;255;255m%s\x1b[0m", command_without_arg, buffer); // print green as valid command, but only color the command, not the arguments
                buffer -= cmd_len;
            } else {
                printf("\x1b[38;2;243;139;168m%s\x1b[0m", buffer); // print red as invalid command
            }
        }
        free(command_without_arg);
        
        if (backspaced) {
            if (buf_len != position) {
                shiftleft(buf_len - position);
            }
            backspaced = false;
        }
        if (insertatmiddle) {
            shiftleft(buf_len - position); // move cursor back to where it was
            insertatmiddle = false;

        }
        // If we have exceeded the buffer, reallocate.
        if ((buf_len + 1) >= bufsize) {
            bufsize += RL_BUFSIZE;
            buffer = realloc(buffer, bufsize);
            if (!buffer) {
                fprintf(stderr, "rush: Error allocating memory\n");
                exit(EXIT_FAILURE);
            }
        }
    }
}

// split line into arguments
char **argsplit(char *line) {
    int bufsize = TOK_BUFSIZE, position = 0;
    char **tokens = malloc(bufsize * sizeof(char*));
    char *token;

    if (!tokens) {
        fprintf(stderr, "rush: Error allocating memory\n");
        exit(EXIT_FAILURE);
    }

    token = strtok(line, TOK_DELIM);
    while (token != NULL) {
        tokens[position] = token;
        position++;

        if (position >= bufsize) {
            bufsize += TOK_BUFSIZE;
            tokens = realloc(tokens, bufsize * sizeof(char*));
            if (!tokens) {
                fprintf(stderr, "rush: Error allocating memory\n");
                exit(EXIT_FAILURE);
            }
        }

        token = strtok(NULL, TOK_DELIM);
    }
    // makes ls and diff have color without user typing it
    if (strcmp(tokens[0], "ls") == 0 || strcmp(tokens[0], "diff") == 0) {
        tokens[position] = "--color=auto";
    }
    position++;
    tokens[position] = NULL;
    return tokens;
}

// continously prompt for command and execute it
void command_loop(char **paths) {
    char *line;
    char **args;
    int status = 1;

    while (status) {
        time_t t = time(NULL);
        struct tm* current_time = localtime(&t); // get current time
        char timestr[256];
        char cwdstr[PATH_MAX];
        if (strftime(timestr, sizeof(timestr), "[%H:%M:%S]", current_time) == 0) { // format time string
            return;
        }
        if (getcwd(cwdstr, sizeof(cwdstr)) == NULL) { // get current working directory
            return;
        }
        char time[256];
        strcpy(time, timestr);
        color_text(time, lavender); // lavender colored time string
        char *cwd = malloc(sizeof(char) * (PATH_MAX + 2));
        sprintf(cwd, "[%s]", cwdstr);
        color_text(cwd, pink); // pink colored current directory
        char arrow[32] = "»";
        color_text(arrow, blue);
        printf("%s %s %s ", time, cwd, arrow);


        line = readline(paths);
        args = argsplit(line);
        status = execute(args);

        free(line);
        free(args);
        free(cwd);
    };
}

int main(int argc, char **argv) {
    // setup
    signal(SIGINT, quit_sig);
    signal(SIGTERM, quit_sig);
    signal(SIGQUIT, quit_sig);
    check_history_file();
    char **paths = setup_path_variable();
    change_terminal_attribute(1); // turn off echoing and disabling getchar requires pressing enter key to return

    command_loop(paths);

    // cleanup
    free(paths);
    change_terminal_attribute(0); // change back to default settings
    return EXIT_SUCCESS;
}