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

/**
 * Copyright 2026 Thorsten Töpper
 *
 * @file file_processor.c
 *
 * 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>


/* https://docs.openssl.org/master/man3/EVP_DigestInit/ */
#include <openssl/evp.h>

#include "file_processor.h"
#include "trace_macros.h"
#include "hex_conversion.h"
#include "kv_manager.h"
#include "database_interaction.h"
#include "options.h"

/*=========== DEFINES, CONSTANTS AND TYPES ===========*/

#ifndef BUFSIZE4MIB
/* Personnal observation: dd bs=4M usually gets good performance regardless of SSD/HDD or USB 2.x/3.x */
#define BUFSIZE4MIB 4194304
#endif


/**
 * Objects from the OpenSSL library
 * Improved later code readability by placing those together and manage outside the file handling code
 */
struct df_md_components {
    EVP_MD_CTX *mdctx_blake2;
    EVP_MD_CTX *mdctx_sha256;
    EVP_MD_CTX *mdctx_sha512;
};


/*=========== GLOBAL VARIABLES ===========*/

/** TODO: Should be set via command line parameter, move to handling when implementing
 */
size_t glbl_bufsize = BUFSIZE4MIB;

const EVP_MD *glbl_md_blake2 = NULL;
const EVP_MD *glbl_md_sha256 = NULL;
const EVP_MD *glbl_md_sha512 = NULL;



/*=========== FUNCTIONS ===========*/
struct df_md_components *init_md_components();
void destroy_md_components(struct df_md_components *pkg);
void print_fileinfo(struct df_fileinfo *info);

/**
 * Prepare a df_md_components struct for active usage.
 */
inline struct df_md_components *init_md_components() {
    struct df_md_components *pkg = NULL;

    if ((pkg=calloc(1,sizeof(struct df_md_components))) == NULL) {
        LOGERR("ERROR: Failed to allocate heap memory for a struct df_md_components errno %d: %s\n",
                errno, strerror(errno));
        return NULL;
    }

    /* TODO: research whether performance difference is really worth this additional complexity,
     * the util is processing files from storage as single thread, not tons of <1KiB blobs in parallel.
     * So a few nano- or microseconds are mostly insignificant compared to the I/O throttle. */
    if (glbl_md_blake2 == NULL) {
        glbl_md_blake2 = EVP_blake2b512();
        if (glbl_md_blake2 == NULL) {
            LOGERR("ERROR: Failed to fetch EVP_MD for BLAKE2\n");
            return NULL;
        }
    }
    if (glbl_md_sha256 == NULL) {
        glbl_md_sha256 = EVP_sha256();
        if (glbl_md_sha256 == NULL) {
            LOGERR("ERROR: Failed to fetch EVP_MD for SHA2_256\n");
            return NULL;
        }
    }
    if (glbl_md_sha512 == NULL) {
        glbl_md_sha512 = EVP_sha512();
        if (glbl_md_sha512 == NULL) {
            LOGERR("ERROR: Failed to fetch EVP_MD for SHA2_512\n");
            return NULL;
        }
    }

    /* Create the contexts */
    if ((pkg->mdctx_blake2 = EVP_MD_CTX_new()) == NULL) {
        LOGERR("ERROR: Failed to create context for BLAKE2\n");
        free(pkg);
        return NULL;
    }

    if ((pkg->mdctx_sha256 = EVP_MD_CTX_new()) == NULL) {
        LOGERR("ERROR: Failed to create context for SHA256\n");
        EVP_MD_CTX_free(pkg->mdctx_blake2);
        free(pkg);
        return NULL;
    }

    if ((pkg->mdctx_sha512 = EVP_MD_CTX_new()) == NULL) {
        LOGERR("ERROR: Failed to create context for SHA512\n");
        EVP_MD_CTX_free(pkg->mdctx_blake2);
        EVP_MD_CTX_free(pkg->mdctx_sha256);
        free(pkg);
        return NULL;
    }

    /* Initialize them */
    if (EVP_DigestInit_ex2(pkg->mdctx_blake2, glbl_md_blake2, NULL) != 1) {
        LOGERR("ERROR: Failed to initialize BLAKE2 context\n");
        EVP_MD_CTX_free(pkg->mdctx_blake2);
        EVP_MD_CTX_free(pkg->mdctx_sha256);
        EVP_MD_CTX_free(pkg->mdctx_sha512);
        free(pkg);
        return NULL;
    }

    if (EVP_DigestInit_ex2(pkg->mdctx_sha256, glbl_md_sha256, NULL) != 1) {
        LOGERR("ERROR: Failed to initialize SHA256 context\n");
        EVP_MD_CTX_free(pkg->mdctx_blake2);
        EVP_MD_CTX_free(pkg->mdctx_sha256);
        EVP_MD_CTX_free(pkg->mdctx_sha512);
        free(pkg);
        return NULL;
    }

    if (EVP_DigestInit_ex2(pkg->mdctx_sha512, glbl_md_sha512, NULL) != 1) {
        LOGERR("ERROR: Failed to initialize SHA512 context\n");
        EVP_MD_CTX_free(pkg->mdctx_blake2);
        EVP_MD_CTX_free(pkg->mdctx_sha256);
        EVP_MD_CTX_free(pkg->mdctx_sha512);
        free(pkg);
        return NULL;
    }

    return pkg;
}

/**
 * Free all memory related to the given struct including itself
 * @param pkg the struct to destroy
 */
inline void destroy_md_components(struct df_md_components *pkg) {
    if (pkg == NULL) {
        return;
    }
    if (pkg->mdctx_blake2 != NULL) {
        EVP_MD_CTX_free(pkg->mdctx_blake2);
    }
    if (pkg->mdctx_sha256 != NULL) {
        EVP_MD_CTX_free(pkg->mdctx_sha256);
    }
    if (pkg->mdctx_sha512 != NULL) {
        EVP_MD_CTX_free(pkg->mdctx_sha512);
    }
    free(pkg);
}


/**
 * Read the file defined by path and name in the argument struct, and add stat
 * results and binary represented hashes of the file into the struct.
 *
 * @param info struct contains the path of the file to read, results will be
 *             stored there.
 *
 * @return 1 if skipped
 *         0 on success
 *        -1 on failure
 */
int process_file(struct df_fileinfo *info) {
    FILE *fdin = NULL;
    char fullpath[4096];
    unsigned char buffer[glbl_bufsize];
    size_t bytes_read;
    struct df_md_components *ctx_pkg;
    bool error_in_loop = false;
    struct df_fileinfo info_from_db;

    unsigned char md_val[EVP_MAX_MD_SIZE];
    unsigned int md_len;

    if (info == NULL || info->name == NULL || info->path == NULL ||
        info->name[0] == '\0' || info->path[0] == '\0') {
        LOGERR("ERROR: Not enough information to construct a full path.\n");
        return -1;
    }


    if (snprintf(fullpath, 4096, "%s/%s", info->path, info->name) < 0) {
        LOGERR("ERROR: Failed to print fullpath string into stack memory: %s (errno %d)\n",
                strerror(errno), errno);
        return -1;
    }

    if (lstat(fullpath, &(info->statbuf)) == -1) {
        LOGERR("ERROR: lstat() call failed for file %s: %s (errno %d)\n",
                fullpath, strerror(errno), errno);
        return -1;
    }

    if ((info->statbuf.st_mode & S_IFMT) != S_IFREG) {
        LOGERR("ERROR: Non-regular files are not processed.\n");
        return -1;
    }

    /* filesystem information collected check whether the DB has a corresponding value,
     * if so check by size and time whether it looks modified if not, skip
     */
    info_from_db.path = info->path;
    info_from_db.name = info->name;
    if ( ! option_force_scan &&
        (dbi_fill_fileinfo(&info_from_db) == 0) &&
        (info->statbuf.st_size == info_from_db.statbuf.st_size) &&
        (info->statbuf.st_mtim.tv_sec < info_from_db.last_seen) &&
        (info->statbuf.st_mtim.tv_sec == info_from_db.statbuf.st_mtim.tv_sec) &&
        (info->statbuf.st_mtim.tv_nsec == info_from_db.statbuf.st_mtim.tv_nsec)) {
        if ( ! option_quiet ) {
            LOGERR("Skip file '%s' file unchanged according to metadata\n", fullpath);
        }
        dbi_update_fileinfo_last_seen(info_from_db.id);
        return 1;
    }


    if ((ctx_pkg = init_md_components()) == NULL) {
        LOGERR("ERROR: Failed to initialize/create md contexts to be used with %s\n",
                fullpath);
        return -1;
    }

    if ((fdin=fopen(fullpath, "rb")) == NULL) {
        LOGERR("ERROR: Failed to open file '%s' %s\n", fullpath, strerror(errno));
        destroy_md_components(ctx_pkg);
        return -1;
    }

    if ( ! option_quiet ) {
        LOGERR("Calculating hashes for file '%s'\n", fullpath);
    }

    /* TODO: proper fread related error handling */
    while (true) {
        bytes_read = fread(buffer, sizeof(unsigned char), glbl_bufsize, fdin);

        if (EVP_DigestUpdate(ctx_pkg->mdctx_blake2, buffer, bytes_read) != 1) {
            LOGERR("ERROR: Failed to update message digest BLAKE2 of file '%s'\n", fullpath);
            error_in_loop = true;
            break;
        }
        if (EVP_DigestUpdate(ctx_pkg->mdctx_sha256, buffer, bytes_read) != 1) {
            LOGERR("ERROR: Failed to update message digest SHA256 of file '%s'\n", fullpath);
            error_in_loop = true;
            break;
        }
        if (EVP_DigestUpdate(ctx_pkg->mdctx_sha512, buffer, bytes_read) != 1) {
            LOGERR("ERROR: Failed to update message digest SHA512 of file '%s'\n", fullpath);
            error_in_loop = true;
            break;
        }
        if (bytes_read != glbl_bufsize) {
            if (feof(fdin) != 0) {
                break;
            }
            if (ferror(fdin) != 0) {
                LOGERR("ERROR: Failed to read from %s: %s (errno %d)\n",
                        fullpath, strerror(errno), errno);
                error_in_loop = true;
                break;
            }
        }
    }
    fclose(fdin);
    fdin = NULL;
    if (error_in_loop) {
        destroy_md_components(ctx_pkg);
        return -1;
    }

    if (EVP_DigestFinal_ex(ctx_pkg->mdctx_blake2, md_val, &md_len) != 1) {
        LOGERR("ERROR: Failed to finalize MD BLAKE2 of file '%s'\n", fullpath);
        destroy_md_components(ctx_pkg);
        return -1;
    }
    convert_from_binary(md_val, md_len, info->hashes.blake2);

    if (EVP_DigestFinal_ex(ctx_pkg->mdctx_sha256, md_val, &md_len) != 1) {
        LOGERR("ERROR: Failed to finalize MD SHA256 of file '%s'\n", fullpath);
        destroy_md_components(ctx_pkg);
        return -1;
    }
    convert_from_binary(md_val, md_len, info->hashes.sha256);

    if (EVP_DigestFinal_ex(ctx_pkg->mdctx_sha512, md_val, &md_len) != 1) {
        LOGERR("ERROR: Failed to finalize MD SHA512 of file '%s'\n", fullpath);
        destroy_md_components(ctx_pkg);
        return -1;
    }
    convert_from_binary(md_val, md_len, info->hashes.sha512);

    destroy_md_components(ctx_pkg);
    return 0;
}

/**
 * Return a file info struct with path and filename fields filled.
 * @param key the fullpath used as key in the gdbm.
 * @return NULL on failure
 */
struct df_fileinfo *prepare_fileinfo(char *key) {
    char *tmp;
    char *fname = NULL;
    size_t plen=0, flen=0;
    struct df_fileinfo *info = NULL;

    if (key == NULL || key[0] == '\0') {
        return NULL;
    }
    if ((fname=strrchr(key, '/')) == NULL) {
        LOGERR("ERROR: path<->filename separation failed with '%s'\n", key);
        return NULL;
    }

    /* At this point the address of fname will always be equal or larger than keys */
    plen = (size_t) (fname - key);
    fname++; /* drop the / */
    flen = strlen(fname);

    if ((info=calloc(1, sizeof(struct df_fileinfo))) == NULL) {
        return NULL;
    }

    if ((tmp = calloc(plen+1, sizeof(char))) == NULL) {
        free(info);
        return NULL;
    }
    memcpy(tmp, key, plen);
    info->path = tmp;

    if ((tmp = calloc(flen+1, sizeof(char))) == NULL) {
        free(info->path);
        free(info);
        return NULL;
    }
    memcpy(tmp, fname, flen);
    info->name = tmp;

    DBGTRC("DEBUG: key '%s' | fname '%s' | info->path '%s' | info->name '%s'\n",
            key, fname, info->path, info->name);

    return info;
}

/**
 * Iterate over the whole gdbm content. If an entry is an unprocessed file,
 * process it, place the information in the database and set it as processed
 * in the storage.
 * @return 0 on success
 *        <0 on failure
 */
int process_gdbm_content() {
    char *key, *tmpkey;
    struct df_fileinfo *info;
    int dbrc = 0, fsrc = 0;

    key = kv_first_key();
    while (key != NULL) {
        DBGTRC("DEBUG: key '%s' | processed:  '%c' | type '%c'\n",
                key, (kv_get_bool(key)) ? 'T' : 'F', kv_get_type(key));

        /* file? already processed? */
        if (kv_get_type(key) == 'D' || kv_get_bool(key)) {
            DBGTRC("DEBUG: Skip directory\n");
            tmpkey = key;
            key = kv_next_key(tmpkey);
            free(tmpkey);
            continue;
        }

        info = prepare_fileinfo(key);
        if (info == NULL) {
            LOGERR("ERROR: Preparing struct for key %s failed.\n", key);
            return -1;
        }
        fsrc = process_file(info);
        if (fsrc < 0) {
            LOGERR("ERROR: Failed to process file %s\n", key);
            free(info->path);
            free(info->name);
            free(info);
            free(key);
            return -1;
        }

#ifdef DEBUGBUILD
        print_fileinfo(info);
#endif
        /* process_file 1 -> skip hashes etc not copied */
        if (fsrc == 0) {
            dbrc = dbi_insert_fileinfo(info);
        }
        free(info->path);
        free(info->name);
        free(info);
        if (dbrc < 0) {
            LOGERR("ERROR: Aborting after database error.\n");
            free(key);
            return -1;
        }


        kv_set_bool(key, true);

        tmpkey = key;
        key = kv_next_key(tmpkey);
        free(tmpkey);
    }

    return 0;
}

inline void print_fileinfo(struct df_fileinfo *info) {
    fprintf(stderr, "info->path = \"%s\"\n", info->path);
    fprintf(stderr, "info->name = \"%s\"\n", info->name);
    fprintf(stderr, "info->hashes.blake2 = \"%s\"\n", info->hashes.blake2);
    fprintf(stderr, "info->hashes.sha256 = \"%s\"\n", info->hashes.sha256);
    fprintf(stderr, "info->hashes.sha512 = \"%s\"\n", info->hashes.sha512);
    fprintf(stderr, "info->statbuf.st_size = \"%ld\"\n", info->statbuf.st_size);
}