/* SPDX-License-Identifier: Apache-2.0 */

/* Copyright 2025 Thorsten Töpper
 *
 * Compare two files with a single SHA1 hash per line
 * useful when comparing filesystem content:
 * find fs_to_check -type f -exec sha1sum "{}" \; > output_1.txt
 * awk ...
 *
 * vim:ts=4:sw=4:expandtab
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <stdbool.h>
#include <stdint.h>
#include <errno.h>
#include <ctype.h>
#include <inttypes.h>

#include "output.h"
#include "hex_conversion.h"
#include "time_utils.h"


#ifndef LINELENGTH
#define LINELENGTH 1024
#endif

/* 8 bytes pointer to a smaller char array? As there are strict conditions in
 * regards to the data which will be processed work with fix size arrays and
 * do math hard coded at compile time. */
#define NON_CONVERTED_SIZE      40
#define FULL_DATABLOCK_SIZE     (NON_CONVERTED_SIZE/2)


struct data_field {
    unsigned char data[FULL_DATABLOCK_SIZE]; /* keep this as first element for bsearch */
#ifdef RAW_DATA_IN_MEMORY
    /* In order to work with streams, the filters and not the raw data is loaded, therefore
     * the field is not required. Keeping it as brain trigger in case this changes in the
     * future. */
    bool active;
#endif
};

struct data_array {
    struct data_field *fields;
    size_t length;
    size_t entry_points[256]; /* performance optimization reduces search area*/
};


void apply_filter_to_array(struct data_field *array, unsigned char *data);
int compare_data_fields(const void *a, const void *b);
int compare_string_data_field(const void *a, const void *b);
void fprint_array(FILE *fd, struct data_array *array);
struct data_array *import_file_into_array(char *filename);
bool is_valid_raw_data(char *s, bool cut);
bool run_file_on_filter_array(struct data_array *da, char *filename, FILE *output);
bool search_data_in_array(struct data_array *da, unsigned char *data);
void sort_array(struct data_array *da);


/* === IMPLEMENTATION === */

/* bsearch, qsort etc. */
int compare_data_fields(const void *a, const void *b) {
    return memcmp(((struct data_field*)a)->data,
            ((struct data_field*)b)->data, FULL_DATABLOCK_SIZE);
}


int compare_string_data_field(const void *a, const void *b) {
    return memcmp((unsigned char*)a,
            ((struct data_field*)b)->data, FULL_DATABLOCK_SIZE);
}


inline bool search_data_in_array(struct data_array *array, unsigned char *data) {
    struct data_field *df;
    size_t entry = 0, rest_length = array->length;

    if (array == NULL || data == NULL) {
        LOGERR("ERROR: Missing argument%s%s\n",
                (array==NULL) ? " array" : "",
                (data ==NULL) ? " data"  : "");
        return false;
    }

    entry = array->entry_points[data[0]];
    if (data[0] == 255 || array->entry_points[data[0]+1] == 0) {
        rest_length = array->length - entry;
    } else {
        rest_length = array->entry_points[data[0]+1] - entry;
    }

    DBGTRC("DEBUG: data[0] = %d (dec) / entry = %lu / rest_length = %lu\n",
            data[0], entry, rest_length);

    df = bsearch(data, &(array->fields[entry]),
            rest_length, sizeof(struct data_field),
            compare_string_data_field);

    /*
    df = bsearch(data, array->fields,
            array->length, sizeof(struct data_field),
            compare_string_data_field);
    */
    if (df != NULL) {
        return true;
    }
    return false;
}


inline void sort_array(struct data_array *da) {
    size_t i = 0, p = 0;
    struct data_field *f;

    if (da == NULL) return;

    qsort(da->fields, da->length, sizeof(struct data_field), compare_data_fields);

    /* set entry points */
    f = da->fields;
    for (i=1,p=0; i<da->length; i++, p++) {
        if (f[p].data[0] != f[i].data[0]) {
            da->entry_points[f[i].data[0]] = i;
            if (f[i].data[0] == 255) {
                break;
            }
        }
    }
}


inline bool is_valid_raw_data(char *s, bool cut) {
    size_t length = 0;
    if (s == NULL) return false;

    length = strlen(s);
    if (length < NON_CONVERTED_SIZE)
            return false;

    if (s[NON_CONVERTED_SIZE] == '\n') {
        length = NON_CONVERTED_SIZE;
    } else {
        while (isspace(s[length-1])) {
            length--;
        }
        if (length != NON_CONVERTED_SIZE)
            return false;
    }

    if ( ! ishex_string(s,NON_CONVERTED_SIZE))
        return false;

    if (cut)
        s[length] = '\0';

    return true;
}


struct data_array *import_file_into_array(char *filename) {
    FILE *fd = NULL;
    char line[LINELENGTH];
    unsigned char data[FULL_DATABLOCK_SIZE];
    size_t line_nr = 0, fpos = 0;
    struct data_array *array = NULL;

    if (filename == NULL || filename[0] == '\0') {
        LOGERR("ERROR: no filename given.\n");
        return NULL;
    }

    if ((fd = fopen(filename, "r")) == NULL) {
        LOGERR("ERROR: Failed to open file '%s': %s (errno %d)\n",
                filename, strerror(errno), errno);
        return NULL;
    }

    /* Count the number of valid lines */
    while (fgets(line, LINELENGTH, fd) != NULL) {
        if (is_valid_raw_data(line, false)) {
            line_nr++;
        }
    }
    fclose(fd);

    /* only complete close and open worked reliably, let's just hope nobody modified the file
     * TODO: compare stat() mtime? */
    if ((fd = fopen(filename, "r")) == NULL) {
        LOGERR("ERROR: Failed to open file '%s': %s (errno %d)\n",
                filename, strerror(errno), errno);
        return NULL;
    }

    if ((array=calloc(1,sizeof(struct data_array))) == NULL) {
        fclose(fd);
        LOGERR("ERROR: Failed to allocate <32 bytes...\n");
        return NULL;
    }
    array->length = line_nr;

    if ((array->fields=calloc(array->length,sizeof(struct data_field))) == NULL) {
        fclose(fd);
        LOGERR("ERROR: Failed to allocate %lu bytes...\n", (array->length * sizeof(struct data_field)));
        return NULL;
    }
    DBGTRC("DEBUG: array->fields[] size is %lu bytesi\n", (array->length * sizeof(struct data_field)));


    while ((fgets(line, LINELENGTH, fd) != NULL) &&
            fpos < array->length) {
        if ( ! is_valid_raw_data(line, true)) {
            continue;
        }

        if (convert_to_binary(line, data) == NULL) {
            LOGERR("ERROR: Failed to convert line %lu into binary data. '%s'\n", line_nr, line);
            free(array->fields);
            free(array);
            fclose(fd);
            return NULL;
        }

        memcpy(array->fields[fpos].data, data, FULL_DATABLOCK_SIZE);
#ifdef RAW_DATA_IN_MEMORY
        array->fields[fpos].active = true;
#endif
        fpos++;
    }

    DBGTRC("DEBUG: valid lines read %lu\n", line_nr);
    fclose(fd);

    return array;
}


bool run_file_on_filter_array(struct data_array *da, char *filename, FILE *output) {
    FILE *fd = NULL, *fdout = output;
    size_t line_nr = 0;
    char line[LINELENGTH];
    unsigned char data[FULL_DATABLOCK_SIZE];

    if (da == NULL || filename == NULL || filename[0] == '\0') {
        LOGERR("ERROR: compromised arguments at call.\n");
        return false;
    }

    if (output == NULL)
        fdout = stdout;

    if ((fd=fopen(filename, "r")) == NULL) {
        LOGERR("ERROR: Failed to open file '%s': %s (errno %d)\n",
                filename, strerror(errno), errno);
        return false;
    }

    /* Be nice and skip and not abort */
    while (fgets(line, LINELENGTH, fd) != NULL) {
        line_nr++;
        DBGTRC("READ LINE %lu: %s", line_nr, line);
        if ( ! is_valid_raw_data(line, true) ) {
            continue;
        }
        if (convert_to_binary(line, data) == NULL) {
            LOGERR("ERROR: Failed to convert line %lu into binary data.\n", line_nr);
            continue;
        }

        if ( ! search_data_in_array(da, data) ) {
            convert_line(line); /* for us only a toupper() loop */
            fputs(line, fdout);
            fputc('\n', fdout);
        }
    }

    fclose(fd);

    return true;
}


void fprint_array(FILE *fd, struct data_array *da) {
    FILE *fdout = stdout;
    char plaintext[NON_CONVERTED_SIZE+1];
    size_t pos;
    if (da == NULL) { return; }
    if (fd != NULL) { fdout = fd; }
    plaintext[NON_CONVERTED_SIZE] = '\0';
    for (pos=0; pos < da->length; pos++) {
        convert_from_binary(da->fields[pos].data, FULL_DATABLOCK_SIZE, plaintext);
        fputs(plaintext, fdout);
        fputc('\n', fdout);
    }
}


int main(int argc, char **argv) {
    FILE *output = NULL;
    int i = 3;
    size_t  s = 0;
    struct data_array *array;
    struct timespec t1, t2, tdiff;

    if (argc < 3) {
        fprintf(stderr, "Usage: %s output filter_file data_file...\n\n", argv[0]);
        fprintf(stderr, "Loads filters into memory, does NOT remove duplicates\n");
        return EXIT_FAILURE;
    }

    s = strlen(argv[1]);
    if (s == 6 && (strncmp("stdout", argv[1], 6) == 0)) {
        output = stdout;
    } else {
        if ((output=fopen(argv[1], "w")) == NULL) {
            LOGERR("ERROR: Failed to open file '%s': %s (errno %d)\n",
                    argv[1], strerror(errno), errno);
            return EXIT_FAILURE;
        }
    }

    LOGERR("IMPORT FILE %s\n", argv[2]);
    array = import_file_into_array(argv[2]);
    if (array == NULL) {
        return EXIT_FAILURE;
    }

    LOGERR("run qsort on in-memory data\n");
    TU_MEASURE_TIME( CLOCK_PROCESS_CPUTIME_ID, &t1, &t2,
    sort_array(array);
    );
    difftime_timespec(t1, t2, &tdiff);
    LOGERR("Sorted in %lu s and %lu ns process CPU time\n", tdiff.tv_sec, tdiff.tv_nsec );

    for (i=3; i<argc; i++) {
        LOGERR("APPLY FILTER ON FILE %s\n", argv[i]);
        if (!run_file_on_filter_array(array, argv[i], output)) {
            LOGERR("ERROR: Aborting.\n");
            return EXIT_FAILURE;
        }
    }
    fflush(output);
    fclose(output);

    free(array->fields);
    free(array);

    return EXIT_SUCCESS;
}