/*
 * MiniVHD	Minimalist VHD implementation in C.
 *
 *		This file is part of the MiniVHD Project.
 *
 *		VHD management functions (open, close, read write etc)
 *
 * Version:	@(#)manage.c	1.0.4	2021/04/16
 *
 * Authors:	Sherman Perry, <shermperry@gmail.com>
 *		Fred N. van Kempen, <waltje@varcem.com>
 *
 *		Copyright 2019-2021 Sherman Perry.
 *		Copyright 2021 Fred N. van Kempen.
 *
 *		MIT License
 *
 *		Permission is hereby granted, free of  charge, to any person
 *		obtaining a copy of this software  and associated documenta-
 *		tion files (the "Software"), to deal in the Software without
 *		restriction, including without limitation the rights to use,
 *		copy, modify, merge, publish, distribute, sublicense, and/or
 *		sell copies of  the Software, and  to permit persons to whom
 *		the Software is furnished to do so, subject to the following
 *		conditions:
 *
 *		The above  copyright notice and this permission notice shall
 *		be included in  all copies or  substantial  portions of  the
 *		Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING  BUT NOT LIMITED TO THE  WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A  PARTICULAR PURPOSE AND NONINFRINGEMENT. IN  NO EVENT  SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER  IN AN ACTION OF  CONTRACT, TORT OR  OTHERWISE, ARISING
 * FROM, OUT OF  O R IN  CONNECTION WITH THE  SOFTWARE OR  THE USE  OR  OTHER
 * DEALINGS IN THE SOFTWARE.
 */
#ifndef _FILE_OFFSET_BITS
# define _FILE_OFFSET_BITS 64
#endif
#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>
#include <stdbool.h>
#include <string.h>
#include <time.h>
#include "minivhd.h"
#include "internal.h"
#include "version.h"
#include "cwalk.h"
#include "xml2_encoding.h"


struct MVHDPaths {
    char     dir_path[MVHD_MAX_PATH_BYTES];
    char     file_name[MVHD_MAX_PATH_BYTES];
    char     w2ku_path[MVHD_MAX_PATH_BYTES];
    char     w2ru_path[MVHD_MAX_PATH_BYTES];
    char     joined_path[MVHD_MAX_PATH_BYTES];
    uint16_t tmp_src_path[MVHD_MAX_PATH_CHARS];
};


int mvhd_errno = 0;


static char tmp_open_path[MVHD_MAX_PATH_BYTES] = {0};


/**
 * \brief Populate data stuctures with content from a VHD footer
 *
 * \param [in] vhdm MiniVHD data structure
 */
static void
read_footer(MVHDMeta* vhdm)
{
    uint8_t buffer[MVHD_FOOTER_SIZE];

    mvhd_fseeko64(vhdm->f, -MVHD_FOOTER_SIZE, SEEK_END);
    (void) !fread(buffer, sizeof buffer, 1, vhdm->f);
    mvhd_buffer_to_footer(&vhdm->footer, buffer);
}


/**
 * \brief Populate data stuctures with content from a VHD sparse header
 *
 * \param [in] vhdm MiniVHD data structure
 */
static void
read_sparse_header(MVHDMeta* vhdm)
{
    uint8_t buffer[MVHD_SPARSE_SIZE] = { 0 };

    mvhd_fseeko64(vhdm->f, vhdm->footer.data_offset, SEEK_SET);
    (void) !fread(buffer, sizeof buffer, 1, vhdm->f);
    mvhd_buffer_to_header(&vhdm->sparse, buffer);
}


/**
 * \brief Validate VHD footer checksum
 *
 * This works by generating a checksum from the footer, and comparing it against the stored checksum.
 *
 * \param [in] vhdm MiniVHD data structure
 */
static bool
footer_checksum_valid(MVHDMeta* vhdm)
{
    return vhdm->footer.checksum == mvhd_gen_footer_checksum(&vhdm->footer);
}


/**
 * \brief Validate VHD sparse header checksum
 *
 * This works by generating a checksum from the sparse header, and comparing it against the stored checksum.
 *
 * \param [in] vhdm MiniVHD data structure
 */
static bool
sparse_checksum_valid(MVHDMeta* vhdm)
{
    return vhdm->sparse.checksum == mvhd_gen_sparse_checksum(&vhdm->sparse);
}


/**
 * \brief Read BAT into MiniVHD data structure
 *
 * The Block Allocation Table (BAT) is the structure in a sparse and differencing VHD which stores
 * the 4-byte sector offsets for each data block. This function allocates enough memory to contain
 * the entire BAT, and then reads the contents of the BAT into the buffer.
 *
 * \param [in] vhdm MiniVHD data structure
 * \param [out] err this is populated with MVHD_ERR_MEM if the calloc fails
 *
 * \retval -1 if an error occurrs. Check value of err in this case
 * \retval 0 if the function call succeeds
 */
static int
read_bat(MVHDMeta *vhdm, MVHDError* err)
{
    vhdm->block_offset = calloc(vhdm->sparse.max_bat_ent, sizeof *vhdm->block_offset);
    if (vhdm->block_offset == NULL) {
        *err = MVHD_ERR_MEM;
        return -1;
    }

    mvhd_fseeko64(vhdm->f, vhdm->sparse.bat_offset, SEEK_SET);

    for (uint32_t i = 0; i < vhdm->sparse.max_bat_ent; i++) {
        (void) !fread(&vhdm->block_offset[i], sizeof *vhdm->block_offset, 1, vhdm->f);
        vhdm->block_offset[i] = mvhd_from_be32(vhdm->block_offset[i]);
    }
    return 0;
}


/**
 * \brief Perform a one-time calculation of some sparse VHD values
 *
 * \param [in] vhdm MiniVHD data structure
 */
static void
calc_sparse_values(MVHDMeta* vhdm)
{
    vhdm->sect_per_block = vhdm->sparse.block_sz / MVHD_SECTOR_SIZE;
    int bm_bytes = vhdm->sect_per_block / 8;
    vhdm->bitmap.sector_count = bm_bytes / MVHD_SECTOR_SIZE;

    if (bm_bytes % MVHD_SECTOR_SIZE > 0) {
        vhdm->bitmap.sector_count++;
    }
}


/**
 * \brief Allocate memory for a sector bitmap.
 *
 * Each data block is preceded by a sector bitmap. Each bit indicates whether the corresponding sector
 * is considered 'clean' or 'dirty' (for sparse VHD images), or whether to read from the parent or current
 * image (for differencing images).
 *
 * \param [in] vhdm MiniVHD data structure
 * \param [out] err this is populated with MVHD_ERR_MEM if the calloc fails
 *
 * \retval -1 if an error occurrs. Check value of err in this case
 * \retval 0 if the function call succeeds
 */
static int
init_sector_bitmap(MVHDMeta* vhdm, MVHDError* err)
{
    vhdm->bitmap.curr_bitmap = calloc(vhdm->bitmap.sector_count, MVHD_SECTOR_SIZE);
    if (vhdm->bitmap.curr_bitmap == NULL) {
        *err = MVHD_ERR_MEM;
        return -1;
    }

    vhdm->bitmap.curr_block = -1;

    return 0;
}


/**
 * \brief Check if the path for a given platform code exists
 *
 * From the available paths, both relative and absolute, construct a full path
 * and attempt to open a file at that path.
 *
 * Note, this function makes no attempt to verify that the path is the correct
 * VHD image, or even a VHD image at all.
 *
 * \param [in] paths a struct containing all available paths to work with
 * \param [in] the platform code to try and obtain a path for. Setting this to zero
 * will try using the directory of the child image
 *
 * \retval true if a file is found
 * \retval false if a file is not found
 */
static bool
mvhd_parent_path_exists(struct MVHDPaths* paths, uint32_t plat_code)
{
    FILE* f;
    int ferr;
    size_t cwk_ret;
    enum cwk_path_style style;

    memset(paths->joined_path, 0, sizeof paths->joined_path);
    style = cwk_path_guess_style((const char*)paths->dir_path);
    cwk_path_set_style(style);
    cwk_ret = 1;

    if (plat_code == MVHD_DIF_LOC_W2RU && *paths->w2ru_path) {
        cwk_ret = cwk_path_join((const char*)paths->dir_path, (const char*)paths->w2ru_path, paths->joined_path, sizeof paths->joined_path);
    } else if (plat_code == MVHD_DIF_LOC_W2KU && *paths->w2ku_path) {
        memcpy(paths->joined_path, paths->w2ku_path, (sizeof paths->joined_path) - 1);
        cwk_ret = 0;
    } else if (plat_code == 0) {
        cwk_ret = cwk_path_join((const char*)paths->dir_path, (const char*)paths->file_name, paths->joined_path, sizeof paths->joined_path);
    }
    if (cwk_ret > MVHD_MAX_PATH_BYTES) {
        return false;
    }

    f = mvhd_fopen((const char*)paths->joined_path, "rb", &ferr);
    if (f != NULL) {
        /* We found a file at the requested path! */
        memcpy(tmp_open_path, paths->joined_path, (sizeof paths->joined_path) - 1);
        tmp_open_path[sizeof tmp_open_path - 1] = '\0';
        fclose(f);
        return true;
    }

    return false;
}


/**
 * \brief attempt to obtain a file path to a file that may be a valid VHD image
 *
 * Differential VHD images store both a UTF-16BE file name (or path), and up to
 * eight "parent locator" entries. Using this information, this function tries to
 * find a parent image.
 *
 * This function does not verify if the path returned is a valid parent image.
 *
 * \param [in] vhdm current MiniVHD data structure
 * \param [out] err any errors that may occurr. Check this if NULL is returned
 *
 * \return a pointer to the global string `tmp_open_path`, or NULL if a path could
 * not be found, or some error occurred
 */
static char*
get_diff_parent_path(MVHDMeta* vhdm, int* err)
{
    int utf_outlen, utf_inlen, utf_ret;
    char *par_fp = NULL;
    struct MVHDPaths *paths;
    size_t dirlen;

    /* We can't resolve relative paths if we don't have an absolute
       path to work with */
    if (!cwk_path_is_absolute((const char*)vhdm->filename)) {
        *err = MVHD_ERR_PATH_REL;
        goto end;
    }

    paths = calloc(1, sizeof *paths);
    if (paths == NULL) {
        *err = MVHD_ERR_MEM;
        goto end;
    }
    cwk_path_get_dirname((const char*)vhdm->filename, &dirlen);
    if (dirlen >= sizeof paths->dir_path) {
        *err = MVHD_ERR_PATH_LEN;
        goto paths_cleanup;
    }
    memcpy(paths->dir_path, vhdm->filename, dirlen);

    /* Get the filename field from the sparse header. */
    utf_outlen = (int)sizeof paths->file_name;
    utf_inlen = (int)sizeof vhdm->sparse.par_utf16_name;
    utf_ret = UTF16BEToUTF8((unsigned char*)paths->file_name, &utf_outlen, (const unsigned char*)vhdm->sparse.par_utf16_name, &utf_inlen);
    if (utf_ret < 0) {
        mvhd_set_encoding_err(utf_ret, err);
        goto paths_cleanup;
    }

    /* Now read the parent locator entries, both relative and absolute, if they exist */
    unsigned char* loc_path;

    for (int i = 0; i < 8; i++) {
        utf_outlen = MVHD_MAX_PATH_BYTES - 1;
        if (vhdm->sparse.par_loc_entry[i].plat_code == MVHD_DIF_LOC_W2RU) {
            loc_path = (unsigned char*)paths->w2ru_path;
        } else if (vhdm->sparse.par_loc_entry[i].plat_code == MVHD_DIF_LOC_W2KU) {
            loc_path = (unsigned char*)paths->w2ku_path;
        } else {
            continue;
        }

        utf_inlen = vhdm->sparse.par_loc_entry[i].plat_data_len;
        if (utf_inlen > MVHD_MAX_PATH_BYTES) {
            *err = MVHD_ERR_PATH_LEN;
            goto paths_cleanup;
        }
        mvhd_fseeko64(vhdm->f, vhdm->sparse.par_loc_entry[i].plat_data_offset, SEEK_SET);
        (void) !fread(paths->tmp_src_path, sizeof (uint8_t), utf_inlen, vhdm->f);

        /* Note, the W2*u parent locators are UTF-16LE, unlike the filename field previously obtained,
           which is UTF-16BE */
        utf_ret = UTF16LEToUTF8(loc_path, &utf_outlen, (const unsigned char*)paths->tmp_src_path, &utf_inlen);
        if (utf_ret < 0) {
            mvhd_set_encoding_err(utf_ret, err);
            goto paths_cleanup;
        }
    }

    /* We have paths in UTF-8. We should have enough info to try and find the parent VHD */
    /* Does the relative path exist? */
    if (mvhd_parent_path_exists(paths, MVHD_DIF_LOC_W2RU)) {
        par_fp = tmp_open_path;
        goto paths_cleanup;
    }

    /* What about trying the child directory? */
    if (mvhd_parent_path_exists(paths, 0)) {
        par_fp = tmp_open_path;
        goto paths_cleanup;
    }

    /* Well, all else fails, try the stored absolute path, if it exists */
    if (mvhd_parent_path_exists(paths, MVHD_DIF_LOC_W2KU)) {
        par_fp = tmp_open_path;
        goto paths_cleanup;
    }

    /* If we reach this point, we could not find a path with a valid file */
    par_fp = NULL;
    *err = MVHD_ERR_PAR_NOT_FOUND;

paths_cleanup:
    free(paths);
    paths = NULL;

end:
    return par_fp;
}


/**
 * \brief Attach the read/write function pointers to read/write functions
 *
 * Depending on the VHD type, different sector reading and writing functions are used.
 * The functions are called via function pointers stored in the vhdm struct.
 *
 * \param [in] vhdm MiniVHD data structure
 */
static void
assign_io_funcs(MVHDMeta* vhdm)
{
    switch (vhdm->footer.disk_type) {
        case MVHD_TYPE_FIXED:
            vhdm->read_sectors = mvhd_fixed_read;
            vhdm->write_sectors = mvhd_fixed_write;
            break;

        case MVHD_TYPE_DYNAMIC:
            vhdm->read_sectors = mvhd_sparse_read;
            vhdm->write_sectors = mvhd_sparse_diff_write;
            break;

        case MVHD_TYPE_DIFF:
            vhdm->read_sectors = mvhd_diff_read;
            vhdm->write_sectors = mvhd_sparse_diff_write;
            break;
    }

    if (vhdm->readonly)
        vhdm->write_sectors = mvhd_noop_write;
}


/**
 * \brief Return the library version as a string
 */
MVHDAPI const char *
mvhd_version(void)
{
    return LIB_VERSION_4;
}


/**
 * \brief Return the library version as a number
 */
MVHDAPI uint32_t
mvhd_version_id(void)
{
    return (LIB_VER_MAJOR << 24) | (LIB_VER_MINOR << 16) |
           (LIB_VER_REV << 16) | LIB_VER_PATCH;
}


/**
 * \brief A simple test to see if a given file is a VHD
 *
 * \param [in] f file to test
 *
 * \retval 1 if f is a VHD
 * \retval 0 if f is not a VHD
 */
MVHDAPI int
mvhd_file_is_vhd(FILE* f)
{
    uint8_t con_str[8] = { 0 };

    if (f == NULL)
        return 0;

    mvhd_fseeko64(f, -MVHD_FOOTER_SIZE, SEEK_END);
    (void) !fread(con_str, sizeof con_str, 1, f);
    if (mvhd_is_conectix_str(con_str))
        return 1;

    return 0;
}


MVHDAPI MVHDGeom
mvhd_calculate_geometry(uint64_t size)
{
    MVHDGeom chs = { 0 };
    uint32_t ts = (uint32_t)(size / MVHD_SECTOR_SIZE);
    uint32_t spt, heads, cyl, cth;

    if (ts > 65535 * 16 * 255)
        ts = 65535 * 16 * 255;

    if (ts >= 65535 * 16 * 63) {
        spt = 255;
        heads = 16;
        cth = ts / spt;
    } else {
        spt = 17;
        cth = ts / spt;
        heads = (cth + 1023) / 1024;
        if (heads < 4)
            heads = 4;
        if (cth >= (heads * 1024) || heads > 16) {
            spt = 31;
            heads = 16;
            cth = ts / spt;
        }
        if (cth >= (heads * 1024)) {
            spt = 63;
            heads = 16;
            cth = ts / spt;
        }
    }

    cyl = cth / heads;
    chs.heads = heads;
    chs.spt = spt;
    chs.cyl = cyl;

    return chs;
}


MVHDAPI MVHDMeta*
mvhd_open(const char* path, int readonly, int* err)
{
    MVHDError open_err = { 0 };

    MVHDMeta *vhdm = calloc(sizeof *vhdm, 1);
    if (vhdm == NULL) {
        *err = MVHD_ERR_MEM;
        goto end;
    }

    if (strlen(path) >= sizeof vhdm->filename) {
        *err = MVHD_ERR_PATH_LEN;
        goto cleanup_vhdm;
    }

    //This is safe, as we've just checked for potential overflow above
    strcpy(vhdm->filename, path);

    if (readonly)
        vhdm->f = mvhd_fopen((const char*)vhdm->filename, "rb", err);
    else
        vhdm->f = mvhd_fopen((const char*)vhdm->filename, "rb+", err);
    if (vhdm->f == NULL) {
        /* note, mvhd_fopen sets err for us */
        goto cleanup_vhdm;
    }
    vhdm->readonly = readonly;

    if (!mvhd_file_is_vhd(vhdm->f)) {
        *err = MVHD_ERR_NOT_VHD;
        goto cleanup_file;
    }

    read_footer(vhdm);
    if (!footer_checksum_valid(vhdm)) {
        *err = MVHD_ERR_FOOTER_CHECKSUM;
        goto cleanup_file;
    }
    if (vhdm->footer.disk_type == MVHD_TYPE_DIFF || vhdm->footer.disk_type == MVHD_TYPE_DYNAMIC) {
        read_sparse_header(vhdm);
        if (!sparse_checksum_valid(vhdm)) {
            *err = MVHD_ERR_SPARSE_CHECKSUM;
            goto cleanup_file;
        }
        if (read_bat(vhdm, &open_err) == -1) {
            *err = open_err;
            goto cleanup_file;
        }
        calc_sparse_values(vhdm);
        if (init_sector_bitmap(vhdm, &open_err) == -1) {
            *err = open_err;
            goto cleanup_bat;
        }
    } else if (vhdm->footer.disk_type != MVHD_TYPE_FIXED) {
        *err = MVHD_ERR_TYPE;
        goto cleanup_bitmap;
    }
    assign_io_funcs(vhdm);

    vhdm->format_buffer.zero_data = calloc(64, MVHD_SECTOR_SIZE);
    if (vhdm->format_buffer.zero_data == NULL) {
        *err = MVHD_ERR_MEM;
        goto cleanup_bitmap;
    }

    vhdm->format_buffer.sector_count = 64;
    if (vhdm->footer.disk_type == MVHD_TYPE_DIFF) {
        char* par_path = get_diff_parent_path(vhdm, err);
        if (par_path == NULL)
            goto cleanup_format_buff;

        uint32_t par_mod_ts = mvhd_file_mod_timestamp(par_path, err);
        if (*err != 0)
            goto cleanup_format_buff;

        if (vhdm->sparse.par_timestamp != par_mod_ts) {
            /* The last-modified timestamp is to fragile to make this a fatal error.
               Instead, we inform the caller of the potential problem. */
            *err = MVHD_ERR_TIMESTAMP;
        }
        vhdm->parent = mvhd_open(par_path, true, err);
        if (vhdm->parent == NULL)
            goto cleanup_format_buff;

        if (memcmp(vhdm->sparse.par_uuid, vhdm->parent->footer.uuid, sizeof vhdm->sparse.par_uuid) != 0) {
            *err = MVHD_ERR_INVALID_PAR_UUID;
            goto cleanup_format_buff;
        }
    }

    /*
     * If we've reached this point, we are good to go,
     * so skip the cleanup steps.
     */
    goto end;

cleanup_format_buff:
    free(vhdm->format_buffer.zero_data);
    vhdm->format_buffer.zero_data = NULL;

cleanup_bitmap:
    free(vhdm->bitmap.curr_bitmap);
    vhdm->bitmap.curr_bitmap = NULL;

cleanup_bat:
    free(vhdm->block_offset);
    vhdm->block_offset = NULL;

cleanup_file:
    fclose(vhdm->f);
    vhdm->f = NULL;

cleanup_vhdm:
    free(vhdm);
    vhdm = NULL;

end:
    return vhdm;
}


MVHDAPI void
mvhd_close(MVHDMeta* vhdm)
{
    if (vhdm == NULL)
        return;

    if (vhdm->parent != NULL)
        mvhd_close(vhdm->parent);

    fclose(vhdm->f);

    if (vhdm->block_offset != NULL) {
        free(vhdm->block_offset);
        vhdm->block_offset = NULL;
    }
    if (vhdm->bitmap.curr_bitmap != NULL) {
        free(vhdm->bitmap.curr_bitmap);
        vhdm->bitmap.curr_bitmap = NULL;
    }
    if (vhdm->format_buffer.zero_data != NULL) {
        free(vhdm->format_buffer.zero_data);
        vhdm->format_buffer.zero_data = NULL;
    }

    free(vhdm);
}


MVHDAPI int
mvhd_diff_update_par_timestamp(MVHDMeta* vhdm, int* err)
{
    uint8_t sparse_buff[1024] = { 0 };

    if (vhdm == NULL || err == NULL) {
        *err = MVHD_ERR_INVALID_PARAMS;
        return -1;
    }
    if (vhdm->footer.disk_type != MVHD_TYPE_DIFF) {
        *err = MVHD_ERR_TYPE;
        return -1;
    }
    char* par_path = get_diff_parent_path(vhdm, err);
    if (par_path == NULL) {
        return -1;
    }
    uint32_t par_mod_ts = mvhd_file_mod_timestamp(par_path, err);
    if (*err != 0) {
        return -1;
    }

    /* Update the timestamp and sparse header checksum */
    vhdm->sparse.par_timestamp = par_mod_ts;
    vhdm->sparse.checksum = mvhd_gen_sparse_checksum(&vhdm->sparse);

    /* Generate and write the updated sparse header */
    mvhd_header_to_buffer(&vhdm->sparse, sparse_buff);
    mvhd_fseeko64(vhdm->f, (int64_t)vhdm->footer.data_offset, SEEK_SET);
    fwrite(sparse_buff, sizeof sparse_buff, 1, vhdm->f);

    return 0;
}


MVHDAPI int
mvhd_read_sectors(MVHDMeta* vhdm, uint32_t offset, int num_sectors, void* out_buff)
{
    return vhdm->read_sectors(vhdm, offset, num_sectors, out_buff);
}


MVHDAPI int
mvhd_write_sectors(MVHDMeta* vhdm, uint32_t offset, int num_sectors, void* in_buff)
{
    return vhdm->write_sectors(vhdm, offset, num_sectors, in_buff);
}


MVHDAPI int
mvhd_format_sectors(MVHDMeta* vhdm, uint32_t offset, int num_sectors)
{
    int num_full = num_sectors / vhdm->format_buffer.sector_count;
    int remain = num_sectors % vhdm->format_buffer.sector_count;

    for (int i = 0; i < num_full; i++) {
        vhdm->write_sectors(vhdm, offset, vhdm->format_buffer.sector_count, vhdm->format_buffer.zero_data);
        offset += vhdm->format_buffer.sector_count;
    }

    vhdm->write_sectors(vhdm, offset, remain, vhdm->format_buffer.zero_data);

    return 0;
}


MVHDAPI MVHDType
mvhd_get_type(MVHDMeta* vhdm)
{
    return vhdm->footer.disk_type;
}