// Setting _DEFAULT_SOURCE is necessary to activate visibility of
// certain header file contents on GNU/Linux systems.
#define _DEFAULT_SOURCE

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

#include <sys/types.h>
#include <sys/stat.h>
#include <fts.h>

// err.h contains various nonstandard BSD extensions, but they are
// very handy.
#include <err.h>

#include <pthread.h>

#include "job_queue.h"

struct job_queue q;

int fauxgrep_file(char const *needle, char const *path) {
    FILE *f = fopen(path, "r");

    if (f == NULL) {
        warn("failed to open %s", path);
        return -1;
    }

    char *line = NULL;
    size_t linelen = 0;
    int lineno = 1;

    while (getline(&line, &linelen, f) != -1) {
        if (strstr(line, needle) != NULL) {
            printf("%s:%d: %s", path, lineno, line);
        }

        lineno++;
    }

    free(line);
    fclose(f);

    return 0;
}

void* fauxgrep_thread(void* arg) {
    char* needle = arg;
    char const* path;
    while (job_queue_pop(&q, (void**) &path) == 0) {
        fauxgrep_file(needle, path);
    }
    return NULL;
}

int main(int argc, char * const *argv) {
    if (argc < 3 || (argc == 4 && strcmp(argv[1], "-n") == 0)) {
        err(1, "usage: [-n INT] STRING paths...");
        exit(1);
    }

    int num_threads = 1;
    char const *needle = argv[1];
    char * const *paths = &argv[2];


    if (argc > 3 && strcmp(argv[1], "-n") == 0) {
        // Since atoi() simply returns zero on syntax errors, we cannot
        // distinguish between the user entering a zero, or some
        // non-numeric garbage.    In fact, we cannot even tell whether the
        // given option is suffixed by garbage, i.e. '123foo' returns
        // '123'.    A more robust solution would use strtol(), but its
        // interface is more complicated, so here we are.
        num_threads = atoi(argv[2]);

        if (num_threads < 1) {
            err(1, "invalid thread count: %s", argv[2]);
        }

        needle = argv[3];
        paths = &argv[4];

    } else {
        needle = argv[1];
        paths = &argv[2];
    }

    job_queue_init(&q, 64);
    pthread_t threads[num_threads];

    for (int i = 0 ; i < num_threads ; i++) {
        pthread_create(&threads[i], NULL, fauxgrep_thread, strdup(needle));
    }

    // FTS_LOGICAL = follow symbolic links
    // FTS_NOCHDIR = do not change the working directory of the process
    //
    // (These are not particularly important distinctions for our simple
    // uses.)
    int fts_options = FTS_LOGICAL | FTS_NOCHDIR;

    FTS *ftsp;
    if ((ftsp = fts_open(paths, fts_options, NULL)) == NULL) {
        err(1, "fts_open() failed");
        return -1;
    }

    FTSENT *p;
    while ((p = fts_read(ftsp)) != NULL) {
        switch (p->fts_info) {
        case FTS_D:
            break;
        case FTS_F:
            job_queue_push(&q, strdup(p->fts_path));
            break;
        default:
            break;
        }
    }

    fts_close(ftsp);

    job_queue_destroy(&q);

    for (int i = 0 ; i < num_threads ; i++) {
        pthread_join(threads[i], NULL);
    }

    return 0;
}
