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

#if defined(_WIN32) || defined(_WIN64)
    #define HAVE_WINDOWS 1
#else
    #define HAVE_WINDOWS 0
#endif

#if HAVE_WINDOWS && (defined(_MSC_BUILD) || defined(_MSC_VER) || defined(_MSC_EXTENSIONS))
    #define HAVE_MSVC 1
#else
    #define HAVE_MSVC 0
#endif

#if HAVE_WINDOWS && (defined(__MINGW32__) || defined(__MINGW64__))
    #define HAVE_MINGW 1
#else
    #define HAVE_MINGW 0
#endif

#if HAVE_WINDOWS
    #if HAVE_MSVC
        #include <io.h>
        #if !defined(F_OK)
            #define F_OK 0
        #endif
        typedef long long ssize_t;
        typedef unsigned long long size_t;
    #endif

    #if HAVE_MINGW
        #include <dirent.h>
    #endif

    #include <direct.h>
    #include <windows.h>
    #define DIRSEP_C '\\'
    #define DIRSEP_S "\\"
    #define PATHSEP_C ';'
    #define PATHSEP_S ";"
    #define PATHVAR "path"
    #define mkdir(X, Y) mkdir(X)
    #define mkstemp _mktemp
#else
    #include <limits.h>
    #include <dirent.h>
    #include <sys/stat.h>
    #include <unistd.h>
    #include <pwd.h>
    #include <errno.h>
    #define DIRSEP_C '/'
    #define DIRSEP_S "/"
    #define PATHSEP_C ':'
    #define PATHSEP_S ":"
    #define PATHVAR "PATH"
#endif

#if !defined(PATH_MAX)
#define PATH_MAX 1024
#endif

#define ARG(X) strcmp(argv[i], X) == 0
#define ARG_VERIFY_NEXT() (argv[i+1] != NULL)

char *program_name;
char *homedir;
char journalroot[PATH_MAX] = {0};
char intermediates[PATH_MAX] = {0};
const char *VERSION = "1.0.0";
const char *FMT_HEADER = "## date:   %s\n"
                         "## time:   %s\n"
                         "## author: %s\n"
                         "## host:   %s\n";
const char *USAGE_STATEMENT = \
    "usage: %s [-h] [-V] [-dDy] [-]\n\n"
    "Weekly Report Generator v%s\n\n"
    "Options:\n"
    "--help             -h        Show this usage statement\n"
    "--dump-relative    -d        Dump records relative to current week\n"
    "--dump-absolute    -D        Dump records by week value\n"
    "--dump-year        -y        Set dump-[relative|absolute] year\n"
    "--version          -V        Show version\n";

void usage() {
    char *name;
    unsigned is_base;

    is_base = 0;
    name = strrchr(program_name, DIRSEP_C);
    if (name != NULL) {
        is_base = 1;
    }
    printf(USAGE_STATEMENT, is_base ? name + 1 : program_name, VERSION);
}

char *find_program(const char *name) {
    static char exe[PATH_MAX] = {0};
    char *token;
    char *pathvar;
    char *abs_prefix[] = {
        "/", "./", ".\\"
    };
    int found_extension;

    for (size_t i = 0; i < sizeof(abs_prefix) / sizeof(char *); i++) {
        if ((strlen(name) > 1 && name[1] == ':') || !strncmp(name, abs_prefix[i], strlen(abs_prefix[i]))) {
            strcpy(exe, name);
            return exe;
        }
    }

    pathvar = getenv(PATHVAR);
    if (!pathvar) {
        return NULL;
    }

    token = strtok(pathvar, PATHSEP_S);
    while (token != NULL) {
        char filename[PATH_MAX] = {0};
        sprintf(filename, "%s%c%s", token, DIRSEP_C, name);
#if HAVE_WINDOWS
        // I am aware of PATHEXT. Let's stick to binary executables and shell scripts
        char *ext[] = {".bat", ".cmd", ".com", ".exe"};
        char filename_orig[PATH_MAX] = {0};

        found_extension = 0;
        for (size_t i = 0; i < sizeof(ext) / sizeof(char *); i++) {
            if (strstr(filename, ext[i]) != NULL) {
                found_extension = 1;
                break;
            }
        }
        if (!found_extension) {
            for (size_t i = 0; i < sizeof(ext) / sizeof(char *); i++) {
                strcpy(filename_orig, filename);
                strcat(filename, ext[i]);
                if (access(filename, F_OK) == 0) {
                    strcpy(exe, filename);
                    return exe;
                }
                strcpy(filename, filename_orig);
            }
        } else {
            if (access(filename, F_OK) == 0) {
                strcpy(exe, filename);
                return exe;
            }
        }
#else
        if (access(filename, F_OK) == 0) {
            strcpy(exe, filename);
            return exe;
        }
#endif
        token = strtok(NULL, PATHSEP_S);
    }
    return NULL;
}

int edit_file(const char *filename) {
    char editor[255] = {0};
    char editor_cmd[PATH_MAX] = {0};
    int result;
    const char *user_editor;

    // Allow the user to override the default editor (vi/notepad)
    user_editor = getenv("EDITOR");
    if (user_editor != NULL) {
        strcpy(editor, find_program(user_editor));
    } else {
        char *editor_path;
        editor_path = find_program("vim");
        if (editor_path != NULL) {
            strcpy(editor, editor_path);
        }
#if HAVE_WINDOWS
        else {
            strcpy(editor, "notepad");
        }
#endif
    }

    if (!find_program(editor)) {
        fprintf(stderr, "Unable to find editor: %s\n", editor);
        exit(1);
    }

    // Tell editor to jump to the end of the file (when supported)
    if(strstr(editor, "vim") || strstr(editor, "vi")) {
        strcat(editor, " +");
    } else if (strstr(editor, "nano") != NULL) {
        strcat(editor, " +9999");
    }

    sprintf(editor_cmd, "%s %s", editor, filename);
    result = system(editor_cmd);
    return result;
}

int make_path(char *basepath) {
    return mkdir(basepath, 0755);
}

char *make_output_path(char *basepath, char *path, int year, int week, int day_of_week) {
    strcpy(path, basepath);
    // Add trailing slash if it's not there
    if (strlen(basepath) > 0 && strlen(basepath) - 1 != DIRSEP_C) {
        strcat(path, DIRSEP_S);
    }

    make_path(path);
    // year
    sprintf(path + strlen(path), "%d%c", year, DIRSEP_C);
    make_path(path);
    // week of year
    sprintf(path + strlen(path), "%d%c", week, DIRSEP_C);
    make_path(path);
    // day of that week
    sprintf(path + strlen(path), "%d", day_of_week);

    return path;
}

ssize_t get_file_size(const char *filename) {
    ssize_t result;
    FILE *fp;
    fp = fopen(filename, "r");
    if (!fp) {
        return -1;
    }
    fseek(fp, 0, SEEK_END);
    result = ftell(fp);
    fclose(fp);
    return result;
}

char *init_tempfile(const char *basepath, char *data) {
    FILE *fp;
    static char tempfile[PATH_MAX];
    sprintf(tempfile, "%s%cweekly.XXXXXX", basepath, DIRSEP_C);
    if ((mkstemp(tempfile)) < 0) {
        return NULL;
    }
    unlink(tempfile);

    fp = fopen(tempfile, "w+");
    if (data != NULL) {
        fprintf(fp, "%s\n", data);
    }
    fclose(fp);

    if (chmod(tempfile, 0600) < 0) {
        return NULL;
    }
    return tempfile;
}

int append_stdin(const char *filename) {
    FILE *fp;
    size_t bufsz;
    char *buf;

    bufsz = BUFSIZ;
    buf = malloc(bufsz);
    if (!buf) {
        return -1;
    }

    fp = fopen(filename, "a");
    if (!fp) {
        perror(filename);
        return -1;
    }

#if HAVE_WINDOWS
    while (fgets(buf, (int) bufsz, stdin) != NULL) {
        fprintf(fp, "%s", buf);
    }
#else
    while (getline(&buf, &bufsz, stdin) >= 0) {
        fprintf(fp, "%s", buf);
    }
#endif
    free(buf);
    fclose(fp);
    return 0;
}

int append_contents(const char *dest, const char *src) {
    char buf[BUFSIZ] = {0};
    FILE *fpi, *fpo;

    fpi = fopen(src, "r");
    if (!fpi) {
        perror(src);
        return -1;
    }

    fpo = fopen(dest, "a");
    if (!fpo) {
        perror(dest);
        return -1;
    }

    // Append source file to destination file
    while (fgets(buf, sizeof(buf), fpi) != NULL) {
        fprintf(fpo, "%s", buf);
    }
    fprintf(fpo, "\n");

    fclose(fpo);
    fclose(fpi);
    return 0;
}

int dump_file(const char *filename) {
    char buf[BUFSIZ] = {0};
    FILE *fp;
    fp = fopen(filename, "r");
    if (!fp) {
        return -1;
    }
    while ((fgets(buf, BUFSIZ, fp)) != NULL) {
        printf("%s", buf);
    }
    fclose(fp);
    return 0;
}

#if HAVE_MSVC
int dir_empty (const char *path) {
    HANDLE hd;
    WIN32_FIND_DATA data;
    size_t i;
    char winpath[PATH_MAX] = {0};

    i = 0;
    sprintf(winpath, "%s%c*.*", path, DIRSEP_C);
    if ((hd = FindFirstFile(path, &data)) != INVALID_HANDLE_VALUE) {
        do {
            i++;
        } while (FindNextFile(hd, &data) != 0);
        FindClose(hd);
    } else {
        return -1;
    }
    return i != 0;
}
#else
int dir_empty(const char *path) {
    DIR *dir;
    struct dirent *dp;
    size_t i;

    dir = opendir(path);
    if (!dir) {
        return -1;
    }

    i = 0;
    while ((dp = readdir(dir)) != NULL) {
        if (strcmp(dp->d_name, ".") == 0 || strcmp(dp->d_name, "..") == 0) {
            continue;
        }
        i++;
    }
    closedir(dir);
    return i != 0;
}
#endif

int dump_week(const char *root, int year, int week) {
    char path_week[PATH_MAX] = {0};
    char path_year[PATH_MAX] = {0};
    const int max_days = 7;

    sprintf(path_year, "%s%c%d", root, DIRSEP_C, year);
    sprintf(path_week, "%s%c%d%c%d", root, DIRSEP_C, year, DIRSEP_C, week);

    if (!dir_empty(path_year)) {
        return -1;
    }

    for (int i = 0; i < max_days; i++) {
        char tmp[PATH_MAX];
        sprintf(tmp, "%s%c%d", path_week, DIRSEP_C, i);
        dump_file(tmp);
    }
    return 0;
}

int main(int argc, char *argv[]) {
    // System info
    char sysname[255] = {0};
    char username[255] = {0};
#if HAVE_WINDOWS
    DWORD usernamesz;
    usernamesz = sizeof(username);
    DWORD sysnamesz;
    sysnamesz = sizeof(sysname);
    homedir = getenv("USERPROFILE");
#else
    struct passwd *user;
    homedir = getenv("HOME");
#endif

    // Time and datestamp
    time_t t;
    struct tm *tm_;
    int year, week, day_of_week;
    char datestamp[255] = {0};
    char timestamp[255] = {0};

    // Path and data buffers
    char *tempfile;
    char journalfile[PATH_MAX] = {0};
    char header[255];

    // Argument triggers
    int do_stdin;
    int do_dump;
    int do_year;
    int uyear;
    char *uyear_error;
    int uweek;
    char *uweek_error;

    // Set program name
    program_name = argv[0];
    // Get current time
    t = time(NULL);
    // Populate tm struct
    tm_ = localtime(&t);
    // Time data fix ups
    year = tm_->tm_year + 1900;
    week = (tm_->tm_yday + 7 - (tm_->tm_wday ? (tm_->tm_wday - 1) : 6)) / 7;
    day_of_week = tm_->tm_wday;

#if HAVE_WINDOWS
    // Get system name
    if(!GetComputerName(sysname, &sysnamesz)) {
        perror("Unable to get system host name");
        strcpy(sysname, "unknown");
    }
    // Get user information
    if(!GetUserName(username, &usernamesz)) {
        perror("Unable to read account information");
        strcpy(username, "unknown");
    }
#else
    // Get system name
    if (gethostname(sysname, sizeof(sysname) - 1) < 0) {
        perror("Unable to get system host name");
        strcpy(sysname, "unknown");
    }

    // Get user information
    user = getpwuid(getuid());
    if (user == NULL) {
        perror("Unable to read account information");
        strcpy(username, "unknown");
    } else {
        strcpy(username, user->pw_name);
    }
#endif
    // Get data;
    strftime(datestamp, sizeof(datestamp) - 1, "%m/%d/%Y", tm_);
    strftime(timestamp, sizeof(timestamp) - 1, "%H:%M:%S", tm_);

    // Populate header string
#if HAVE_WINDOWS
    sprintf(header, FMT_HEADER, datestamp, timestamp, username, sysname);
    sprintf(journalroot, "%s%c.weekly", homedir, DIRSEP_C);
#else
    sprintf(header, FMT_HEADER, datestamp, timestamp, user->pw_name, sysname);
    sprintf(journalroot, "%s%c.weekly", homedir, DIRSEP_C);
#endif
    sprintf(intermediates, "%s%ctmp", journalroot, DIRSEP_C);

    // Prime argument triggers
    do_stdin = 0;
    do_dump = 0;
    do_year = 0;
    uyear = year;
    uweek = week;

    // Parse user arguments
    for (int i = 1; i < argc; i++) {
        if (ARG("-h") || ARG("--help")) {
            usage();
            exit(0);
        }
        if (ARG("-V") || ARG("--version")) {
            puts(VERSION);
            exit(0);
        }
        if (ARG("-")) {
            do_stdin = 1;
        }
        if (ARG("-d") || ARG("--dump-relative")) {
            if (ARG_VERIFY_NEXT()) {
                uweek = (int) strtol(argv[i + 1], &uweek_error, 10);
                if (*uweek_error != '\0') {
                    fprintf(stderr, "Invalid integer\n");
                    exit(1);
                }
                week -= uweek;
            }
            do_dump = 1;
        }
        if (ARG("-D") || ARG("--dump-absolute")) {
            if (ARG_VERIFY_NEXT()) {
                uweek = (int) strtol(argv[i + 1], &uweek_error, 10);
                if (*uweek_error != '\0') {
                    fprintf(stderr, "Invalid integer\n");
                    exit(1);
                }
                week = uweek;
            }
            do_dump = 1;
        }
        if (ARG("-y") || ARG("--dump-year")) {
            if (!ARG_VERIFY_NEXT()) {
                fprintf(stderr, "--dump-year (-y) requires an integer year\n");
                exit(1);
            }
            uyear = (int) strtol(argv[i + 1], &uyear_error, 10);
            if (*uyear_error != '\0') {
                fprintf(stderr, "Invalid integer\n");
                exit(1);
            }
            year = uyear;
            do_year = 1;
        }
    }

    if (do_year && !do_dump) {
        fprintf(stderr, "Option --dump-year (-y) requires options -d or -D\n");
        exit(1);
    }

    if (do_dump) {
        if (week < 0) {
            week = 0;
        }
        if (dump_week(journalroot, year, week) < 0) {
            fprintf(stderr, "No entries found for week %d of %d\n", week, year);
            exit(1);
        }
        exit(0);
    }

    // Create weekly root directory
    make_path(journalroot);

    // Write header string to temporary file
    make_path(intermediates);
    if ((tempfile = init_tempfile(intermediates, header)) == NULL) {
        perror("Unable to create temporary file");
        exit(1);
    }

    // Create new weekly journalfile path
    if (make_output_path(journalroot, journalfile, year, week, day_of_week) < 0) {
        fprintf(stderr, "Unable to create output path: %s (%s)\n", journalfile, strerror(errno));
        perror(journalfile);
        unlink(tempfile);
        exit(1);
    }

    // Get original size of the temporary file
    ssize_t tempfile_size;
    tempfile_size = get_file_size(tempfile);

    if (do_stdin) {
        if (append_stdin(tempfile) < 0) {
            fprintf(stderr, "Failed to read from stdin\n");
            exit(1);
        }
    } else {
        // Open the temporary file with an editor so the user can write their notes
        if (edit_file(tempfile) != 0) {
            fprintf(stderr, "Non-zero exit status from editor. Aborting.\n");
            fprintf(stderr, "Dead entry file: %s\n", tempfile);
            exit(1);
        }
    }

    // Test whether temporary file size increased. If not, die.
    ssize_t tempfile_newsize;
    tempfile_newsize = get_file_size(tempfile);
    if (tempfile_newsize <= tempfile_size) {
        fprintf(stderr, "Empty message, aborting.\n");
        unlink(tempfile);
        exit(1);
    }

    // Copy data from the temporary file to the weekly journal path
    if (append_contents(journalfile, tempfile) < 0) {
        fprintf(stderr, "Unable to append contents of '%s' to '%s' (%s)\n", tempfile, journalfile, strerror(errno));
        exit(1);
    }

    // Nuke the temporary file
    if (unlink(tempfile) < 0) {
        fprintf(stderr, "Unable to remove temporary file: %s (%s)\n", tempfile, strerror(errno));
        exit(1);
    }

    // Inform the user
    printf("Message written to: %s\n", journalfile);
    return 0;
}