/* 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 ...
 *
 * Hashes are converted into binary form and stored in lists in a tree.
 * 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 "trace_macros.h"
#include "hex_conversion.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)
/* The tree can easily cause an immense memory overhead */
#define TREE_MAX_DEPTH          4
#define TREE_BRANCHES           32

struct list_node {
    struct list_node *next;
    unsigned char data[FULL_DATABLOCK_SIZE];
};

struct list_head {
    struct list_node *first_node;
    struct list_node *last_node;
#ifdef DEBUGBUILD
    size_t head_nr;
    size_t length;
#endif
};

struct tree_branch {
    struct tree_branch *branches[TREE_BRANCHES];
    struct list_head *list;
};

struct tree_root {
    struct tree_branch *branches[256];
};

#ifdef DEBUGBUILD
size_t head_numbers = 0;
size_t freed = 0;
#endif

struct list_head *create_list_head();
void destroy_list(struct list_head *head);
int insert_data_into_list(struct list_head *head, unsigned char *data);
int remove_data_from_list(struct list_head *head, char *data);
int check_list_for_data(struct list_head *head, unsigned char *data);
struct tree_root *create_tree_root();
void destroy_tree_branches(struct tree_branch *branch);
void destroy_tree(struct tree_root *root);
int insert_into_tree(struct tree_root *root, unsigned char *data);
int check_tree_for_data(struct tree_root *root, unsigned char *data);
void print_list_plain(struct list_head *head, FILE *fd);
void print_tree_branch(struct tree_branch *branch, FILE *fd);
void print_tree(struct tree_root *root, FILE *fd);



inline struct list_head *create_list_head() {
    struct list_head *head = calloc(1, sizeof(struct list_head));
    if (head == NULL) {
        /* If the following masked fprintf calls fail there was a chance */
        LOGERR("ERROR: Failed to allocate memory for list_head: ");
        fputs(strerror(errno), stderr);
        fputc('\n', stderr);
        return NULL;
    }
    head->first_node = NULL;
    head->last_node = NULL;
#ifdef DEBUGBUILD
    head->head_nr = head_numbers++;
    LOGERR("DEBUG: Create head_nr %lu\n", head->head_nr);
    head->length = 0;
#endif
    return head;
}

inline void destroy_list(struct list_head *head) {
    struct list_node *ptr=NULL;
    if (head == NULL) return;
#ifdef DEBUGBUILD
    char *out = calloc(42,sizeof(char));
    fprintf(stderr, "\n\n\n");
    LOGERR("DEBUG: freed so far %lu\n", freed++);
//if (head->head_nr == 15) {
    LOGERR("DEBUG: head  0x%p\n", head);
    LOGERR("DEBUG: first_node %p\n", head->first_node);
    LOGERR("DEBUG: last_node  %p\n", head->last_node);
    LOGERR("DEBUG: head_nr    %lu\n", head->head_nr);
    LOGERR("DEBUG: length     %lu\n", head->length);
//}
#endif
    while (head->first_node !=  NULL) {
        ptr = head->first_node;
#ifdef DEBUGBUILD
//if (head->head_nr == 15) {
        LOGERR("DEBUG: first_node %p\n", head->first_node);
        LOGERR("ptr        %p\n", ptr);
        LOGERR("ptr->next  %p\n", ptr->next);
        out = convert_from_binary(ptr->data, 20, out);
        LOGERR("data: %p (converted plaintext value: '%s'\n", ptr->data, out);
//}
#endif
        head->first_node = head->first_node->next;
        free(ptr);
    }
    free(head);
    head = NULL;

#ifdef DEBUGBUILD
    free(out);
#endif
}

/* No time consuming duplicate check, data to be processed is expected to be gone sorted through uniq */
inline int insert_data_into_list(struct list_head *head, unsigned char *data) {
    struct list_node *node;
    if (head == NULL || data == NULL) {
        LOGERR("ERROR: Improper arguments.\n");
        return -1;
    }
    if ((node = calloc(1, sizeof(struct list_node))) == NULL) {
        LOGERR("ERROR: Failed to allocate %lu bytes memory for list node: %s\n",
                sizeof(struct list_node), strerror(errno));
        return -2;
    }
    memcpy(node->data, data, FULL_DATABLOCK_SIZE);
    node->next = NULL;
#ifdef DEBUGBUILD
    LOGERR("DEBUG: node %p / node->next %p (nil expected)\n", node, node->next);
#endif
    do {
        if (head->first_node == NULL) {
            head->first_node = node;
            head->last_node = node;
#ifdef DEBUGBUILD
            LOGERR("DEBUG: head %p (nr %lu) / head->first_node %p / head->last_node %p\n",
                    head, head->head_nr, head->first_node, head->last_node);
#endif
            break;
        }
        head->last_node->next = node;
        head->last_node = node;
#ifdef DEBUGBUILD
        LOGERR("DEBUG: head %p (nr %lu) / head->last_node %p / node %p\n",
                head, head->head_nr, head->last_node, node);
#endif
    } while (0);
#ifdef DEBUGBUILD
    head->length++;
#endif
    return 0;
}


inline int remove_data_from_list(struct list_head *head, char *data) {
    struct list_node *node, *prev;
    if (head == NULL || data == NULL) {
        LOGERR("ERROR: Improper arguments.\n");
        return -1;
    }
    node = head->first_node;
    if (node == NULL) {
        return 1;
    }
    /* Check first node in list */
    if (memcmp(node->data, data, FULL_DATABLOCK_SIZE) == 0) {
        head->first_node = node->next;
        free(node);
#ifdef DEBUGBUILD
        head->length--;
#endif
        return 0;
    }

    prev = head->first_node;
    node = head->first_node->next;

    /**/
    while (node != NULL) {
        if (memcmp(node->data, data, FULL_DATABLOCK_SIZE) == 0) {
            prev->next = node->next;
            free(node);
#ifdef DEBUGBUILD
            head->length--;
#endif
            return 0;
        }
        prev = node;
        node = node->next;
    }

    return 1;
}


/* Thread safety mandatory in case mechanisms to remove found entries shall be
 * removed to safe time with future checks. However, in case the input file is
 * sorted, Thread safety has negative performance impact.
 */
inline int check_list_for_data(struct list_head *head, unsigned char *data) {
    struct list_node *node;
    int rc = 1;
    if (head == NULL || data == NULL) {
        LOGERR("ERROR: Improper arguments.\n");
        return -1;
    }

    node = head->first_node;
    while(node != NULL) {
        if (memcmp(node->data, data, FULL_DATABLOCK_SIZE) == 0) {
            rc = 0;
            break;
        }
        node = node->next;
    }

    return rc;
}


inline struct tree_root *create_tree_root() {
    struct tree_root *root = calloc(1, sizeof(struct tree_root));
    if (root == NULL) {
        LOGERR("ERROR: Failed to allocate memory for tree_root");
        fputs(strerror(errno),stderr);
        fputc('\n', stderr);
        return NULL;
    }
    return root;
}

inline void destroy_tree_branches(struct tree_branch *branch) {
    uint16_t i = 0;
    if (branch == NULL)
        return;
    if (branch->list != NULL) {
        destroy_list(branch->list);
    }
    branch->list = NULL;
    for (i=0; i<TREE_BRANCHES; i++) {
        destroy_tree_branches(branch->branches[i]);
        branch->branches[i] = NULL;
    }
}

inline void destroy_tree(struct tree_root *root) {
    uint16_t i;

    for (i=0; i<256; i++) {
        if (root->branches[i] != NULL) {
            destroy_tree_branches(root->branches[i]);
            root->branches[i] = NULL;
        }
    }
    free(root);
}

inline int insert_into_tree(struct tree_root *root, unsigned char *data) {
    int depth = 0, i =0;
    struct tree_branch *ptr = NULL;
    unsigned char uc = 0;

    if (root == NULL || data == NULL) {
        LOGERR("ERROR: Empty argument\n");
        return -1;
    }

    /* tree_root always covers 256 bytes/branches, in order to improve search
     * performance in case the data is sorted use the last byte in this step
     * for parallel searches, less wait-time due to locks. */
    uc = (unsigned char)data[FULL_DATABLOCK_SIZE-1];
    ptr = root->branches[uc];
    if (ptr == NULL) {
        if ((root->branches[uc] = calloc(1, sizeof(struct tree_branch))) == NULL) {
            LOGERR("ERROR: Failed to allocate memory for new tree branch %02X for the root\n", uc);
            return -2;
        }
        ptr = root->branches[uc];
    }
    for (depth = 0; depth < TREE_MAX_DEPTH-1; depth++) {
        uc = ((unsigned char)data[depth]) % TREE_BRANCHES;
        if (ptr->branches[uc] == NULL) {
            if ((ptr->branches[uc]=calloc(1,sizeof(struct tree_branch))) == NULL) {
                LOGERR("ERROR: Failed to allocate memory for new tree branch %02X at depth %d\n", uc, depth);
                return -3;
            }
            for (i=0;i<TREE_BRANCHES;i++) { ptr->branches[uc]->branches[i] = NULL; }
            ptr->branches[uc]->list = NULL;
        }
        ptr = ptr->branches[uc];
    }

    if (ptr->list == NULL) {
        if ((ptr->list = create_list_head()) == NULL) {
            return -4;
        }
    }

    return insert_data_into_list(ptr->list, data);
}



/* Return values:
 * < 0  ERROR  | == 0 FOUND | > 0 NOT FOUND */
inline int check_tree_for_data(struct tree_root *root, unsigned char *data) {
    int depth = 0;
    struct tree_branch *ptr;
    unsigned char uc;
    if (root == NULL || data == NULL) {
        LOGERR("ERROR: Empty argument.\n");
        return -1;
    }
    uc = (unsigned char)data[FULL_DATABLOCK_SIZE-1];
    ptr = root->branches[uc];
    if (ptr == NULL) return 1;

    for (depth=0; depth < TREE_MAX_DEPTH-1; depth++) {
        uc = ((unsigned char)data[depth]) % TREE_BRANCHES;
        if (ptr->branches[uc] == NULL)
            return 1;
        ptr = ptr->branches[uc];
    }
    return check_list_for_data(ptr->list, data);
}


void print_list_plain(struct list_head *head, FILE *fd) {
    struct list_node *ptr = NULL;
    char *out = NULL;

    if (head == NULL) return;

    if (fd == NULL) {
        fd = stdout;
    }

    ptr = head->first_node;
    while (ptr != NULL) {
        out = convert_from_binary(ptr->data, FULL_DATABLOCK_SIZE, out);
        fputs(out, fd);
        fputc('\n', fd);
        ptr = ptr->next;
    }
}


void print_tree_branch(struct tree_branch *branch, FILE *fd) {
    uint16_t i;
    if (branch == NULL) return;
    if (fd == NULL) fd = stdout;
    if (branch->list != NULL)
        print_list_plain(branch->list, fd);
    for (i=0; i<TREE_BRANCHES; i++) {
        print_tree_branch(branch->branches[i], fd);
    }
}

void print_tree(struct tree_root *root, FILE *fd) {
    uint16_t i;
    if (root == NULL) {
        return;
    }
    for (i=0; i<256;i++) {
        print_tree_branch(root->branches[i], fd);
    }
}


struct tree_root *read_file_into_tree(char *filename) {
    size_t line_nr=0;
    struct tree_root *root = NULL;
    FILE *fd = NULL;
    char *line = NULL;
    unsigned char *data = NULL;

    if (filename == NULL || strlen(filename) == 0) {
        return NULL;
    }

    if ((root=create_tree_root()) == NULL) {
        return NULL;
    }

    if ((line=calloc(LINELENGTH,sizeof(char))) == NULL) {
        free(root);
        LOGERR("ERROR: Failed to allocate %d bytes for line buffer\n", LINELENGTH);
        return NULL;
    }

    if ((data=calloc(LINELENGTH/2,sizeof(char))) == NULL) {
        free(root);
        free(line);
        LOGERR("ERROR: Failed to allocate %d bytes for data buffer\n", LINELENGTH/2);
        return NULL;
    }

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

    while (fgets(line, LINELENGTH, fd) != NULL) {
        line_nr++;
        if (convert_line(line)<0) {
            LOGERR("ERROR: Failed to prepare line %lu for conversion.\n", line_nr);
            free(data);
            free(line);
            destroy_tree(root);
            fclose(fd);
            return NULL;
        }

        if (convert_to_binary(line, data) == NULL) {
            free(data);
            free(line);
            destroy_tree(root);
            fclose(fd);
            LOGERR("ERROR: Failed to convert line %lu into binary data.\n", line_nr);
            return NULL;
        }

        if (insert_into_tree(root, data) != 0) {
            free(data);
            free(line);
            destroy_tree(root);
            fclose(fd);
            LOGERR("ERROR: Failed to insert line %lu in binary form into tree.\n", line_nr);
            return NULL;
        }
    }
    free(data);
    free(line);
    fclose(fd);
    return root;
}


int filter_file_with_tree(char *filename, FILE *output, struct tree_root *root) {
    size_t line_nr=0;
    FILE *fd = NULL;
    char *line = NULL;
    unsigned char *data = NULL;
    int check_result = 0;
    int rc = 0;

    if (filename == NULL || root == NULL|| strlen(filename) == 0) {
        return -1;
    }

    if ((line=calloc(LINELENGTH,sizeof(char))) == NULL) {
        LOGERR("ERROR: Failed to allocate %d bytes for line buffer\n", LINELENGTH);
        return -2;
    }

    if ((data=calloc(LINELENGTH/2,sizeof(char))) == NULL) {
        free(line);
        LOGERR("ERROR: Failed to allocate %d bytes for data buffer\n", LINELENGTH/2);
        return -3;
    }

    if ((fd=fopen(filename, "r")) == NULL) {
        free(line);
        free(data);
        LOGERR("ERROR: Failed to open file '%s': %s\n", filename, strerror(errno));
        return -4;
    }

    while (fgets(line, LINELENGTH, fd) != NULL) {
        line_nr++;
        if (convert_line(line)<0) {
            LOGERR("ERROR: Failed to prepare line %lu for conversion.\n", line_nr);
            rc++;
            continue;
        }

        if (convert_to_binary(line, data) == NULL) {
            LOGERR("ERROR: Failed to convert line %lu into binary data.\n", line_nr);
            rc++;
            continue;
        }

        check_result = check_tree_for_data(root, data);
        if (check_result > 0) { /* Not found => print */
            fputs(line, output);
            fputc('\n', output);
        } else if (check_result <  0) {
            LOGERR("ERROR: check function called with invalid arguments at line %lu\n", line_nr);
            rc++;
            continue;
        }
    }
    free(data);
    free(line);
    fclose(fd);

    return rc;
}


#ifdef DEBUGBUILD
int test_list() {
    char *content[20] = {
        "2bc4b40c334a098593dc80d87213862d64ca3651",
        "cc20639230abd1fb3fab4a6416b9587ab8cc62b4",
        "dbb2d4efda208d7004dc9da3dc73e8b428caa4a8",
        "7ce204f222956171dfcd271d6742f337b3be8711",
        "098323d451251c7794829790d40104fccb7cc40f",
        "f0d00ea6c1f155a95bd857faad3502ef1634bc4a",
        "8ced992112e8bd26ead5c5891cc6641bf058a689",
        "2049ffda6ff1cc5daf80bf11e22c2a4731ab7638",
        "f40d8c300351ef8623b365652b0c3e49208e2a08",
        "af5d07d66a9f502c6541b01387daa0a07376c217",
        "2bcdcc73d8f7c8d905b6c9c12ac76ebaed7b6b1c",
        "d6162568f67beddf9322f9f7ac8da2a7913a1cc6",
        "e432a240228a839fa63d600174733c63572f73ab",
        "0b2a5c0f8ef6ba73599e2d5feefd72741cdf8c98",
        "f60619a4ab9a43149b314fc5cbd74edbc7159cce",
        "08416eabffe9fb7a24629ad88b6a519180cd81c0",
        "00031125caea9639a51997e9aa59f5bde49e0417",
        "704163e6519e928d2fc261a515576f556973391c",
        "9485eaf154c185617c2b04ab8d359011ec0c528a",
        "f02ac509cbe3e7634b51030c9058164a36f80815"
    };
    struct list_head *lh = NULL;
    int i = 0, rc = 0;
    unsigned char *data = NULL;

    LOGERR("=== BEGIN LIST TEST ===\n\n");

    data=calloc(LINELENGTH/2, sizeof(unsigned char));

    lh = create_list_head();
    if (lh == NULL) {
        LOGERR("FAILURE: Failed to intialize list head\n");
        rc++;
        return rc;
    }
    for (i=0; i<20; i++) {
        convert_to_binary(content[i],data);
        if (insert_data_into_list(lh, data) != 0) {
            LOGERR("FAILURE: Failed to insert '%s' in binary form into list.\n", content[i]);
            rc++;
        }
    }

    LOGERR("=> Print full list\n");
    print_list_plain(lh, NULL);

    destroy_list(lh);
    LOGERR("\n=== FINISHED LIST TEST ===\n\n");
    return rc;
}


int test_tree() {
    char *content[20] = {
        "2bc4b40c334a098593dc80d87213862d64ca3651",
        "cc20639230abd1fb3fab4a6416b9587ab8cc62b4",
        "dbb2d4efda208d7004dc9da3dc73e8b428caa4a8",
        "7ce204f222956171dfcd271d6742f337b3be8711",
        "098323d451251c7794829790d40104fccb7cc40f",
        "f0d00ea6c1f155a95bd857faad3502ef1634bc4a",
        "8ced992112e8bd26ead5c5891cc6641bf058a689",
        "2049ffda6ff1cc5daf80bf11e22c2a4731ab7638",
        "f40d8c300351ef8623b365652b0c3e49208e2a08",
        "af5d07d66a9f502c6541b01387daa0a07376c217",
        "2bcdcc73d8f7c8d905b6c9c12ac76ebaed7b6b1c",
        "d6162568f67beddf9322f9f7ac8da2a7913a1cc6",
        "e432a240228a839fa63d600174733c63572f73ab",
        "0b2a5c0f8ef6ba73599e2d5feefd72741cdf8c98",
        "f60619a4ab9a43149b314fc5cbd74edbc7159cce",
        "08416eabffe9fb7a24629ad88b6a519180cd81c0",
        "00031125caea9639a51997e9aa59f5bde49e0417",
        "704163e6519e928d2fc261a515576f556973391c",
        "9485eaf154c185617c2b04ab8d359011ec0c528a",
        "f02ac509cbe3e7634b51030c9058164a36f80815"
    };
    struct tree_root *root = NULL;
    int i = 0, rc = 0;
    unsigned char *data = NULL;

    LOGERR("=== BEGIN TREE TEST ===\n\n");

    data=calloc(LINELENGTH/2, sizeof(unsigned char));

    root = create_tree_root();
    if (root == NULL) {
        LOGERR("FAILURE: Failed to intialize tree root\n");
        rc++;
        return rc;
    }
    for (i=0; i<20; i++) {
        convert_to_binary(content[i],data);
        if (insert_into_tree(root, data) != 0) {
            LOGERR("FAILURE: Failed to insert '%s' in binary form into list.\n", content[i]);
            rc++;
        }
    }

    print_tree(root, NULL);

    destroy_tree(root);
    LOGERR("\n=== FINISHED TREE TEST ===\n\n");
    return rc;
}
#endif


int main(int argc, char **argv) {
    FILE *output = NULL;
    struct tree_root *root = NULL;
    int filter_rc = 0;

#ifdef DEBUGBUILD
    if (test_list() != 0) {
        LOGERR("ABORT OTHER TESTS.\n");
        return EXIT_FAILURE;
    }
    if (test_tree() != 0) {
        LOGERR("ABORT OTHER TESTS.\n");
        return EXIT_FAILURE;
    }
    return EXIT_SUCCESS;
#endif

    if (argc != 4) {
        fprintf(stderr, "Usage: %s raw_data filter_file output_file\n", argv[0]);
        fprintf(stderr, "\toutput_file - if set to 'stdout' the stream is used\n");
        fprintf(stderr, "\t            - appends to file, not overwrite\n");
        return EXIT_FAILURE;
    }

    fprintf(stderr, "raw data %s\n", argv[1]);
    fprintf(stderr, "filter   %s\n", argv[2]);
    fprintf(stderr, "output   %s\n", argv[3]);


    if (strncmp(argv[3], "stdout", 7) == 0) {
        output = stdout;
    } else {
        if ((output = fopen(argv[3], "a")) == NULL) {
            LOGERR("ERROR: Failed to open file '%s': %s\n", argv[3], strerror(errno));
            return EXIT_FAILURE;
        }
    }

    fprintf(stderr, "Read file '%s' into memory\n", argv[2]);
    root = read_file_into_tree(argv[2]);
    fprintf(stderr, "Begin filtering file '%s'\n", argv[1]);
    filter_rc = filter_file_with_tree(argv[1], output, root);
    fflush(output);
    fclose(output);
    fprintf(stderr, "Filtering finished, cleaning up.\n");
    destroy_tree(root);

    if (filter_rc != 0) {
        LOGERR("problems during application of filter, check stderr for error messages\n");
    }

    return filter_rc;
}