/* vi: set expandtab sw=4 sts=4: */
/* opkg_archive.c - the opkg package management system

   Copyright (C) 2014 Paul Barker

   This program is free software; you can redistribute it and/or
   modify it under the terms of the GNU General Public License as
   published by the Free Software Foundation; either version 2, or (at
   your option) any later version.

   This program is distributed in the hope that it will be useful, but
   WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   General Public License for more details.
*/

#include "config.h"

#include <archive.h>
#include <archive_entry.h>
#include <malloc.h>
#include <stdio.h>
#include <string.h>

#include "opkg_message.h"
#include "opkg_archive.h"
#include "file_util.h"
#include "sprintf_alloc.h"
#include "xfuncs.h"

/*******************************************************************************
 * internal functions
 */

struct inner_data {
    /* Pointer to the original archive file we're extracting from. */
    struct archive *outer;

    /* Buffer for extracted data. */
    void *buffer;
};

static ssize_t inner_read(struct archive *a, void *client_data,
                          const void **buff)
{
    (void)a;

    struct inner_data *data = (struct inner_data *)client_data;

    *buff = data->buffer;
    return archive_read_data(data->outer, data->buffer, EXTRACT_BUFFER_LEN);
}

static int inner_close(struct archive *inner, void *client_data)
{
    (void)inner;

    struct inner_data *data = (struct inner_data *)client_data;

    archive_read_free(data->outer);
    free(data->buffer);
    free(data);

    return ARCHIVE_OK;
}

/* Read data from an archive into a buffer. Returns 0 on error as the return
 * value is an unsigned size_t. If an eof pointer is provided, it will be set to
 * 1 on EOF or 0 otherwise.
 */
static size_t read_data(struct archive *a, void *buffer, size_t len, int *eof)
{
    ssize_t r;
    int retries = 0;

    if (eof)
        *eof = 0;

 retry:
    /* Read data into buffer. */
    r = archive_read_data(a, buffer, len);
    if (r > 0) {
        /* We got good data. */
        return (size_t) r;
    }
    switch (r) {
    case 0:
        /* We reached EOF. */
        if (eof)
            *eof = 1;
        return 0;

    case ARCHIVE_WARN:
        /* We don't know the size read so we have to treat this
         * as an error.
         */
        opkg_msg(ERROR, "Warning when reading data from archive: %s\n",
                 archive_error_string(a));
        return 0;

    case ARCHIVE_RETRY:
        opkg_msg(ERROR, "Failed to read data from archive: %s\n",
                 archive_error_string(a));
        if (retries++ < 3) {
            opkg_msg(NOTICE, "Retrying...");
            goto retry;
        } else
            return 0;

    default:
        opkg_msg(ERROR, "Failed to read data from archive: %s\n",
                 archive_error_string(a));
        return 0;
    }
}

static int copy_to_stream(struct archive *a, FILE * stream)
{
    void *buffer;
    size_t sz_out, sz_in;
    int eof;
    size_t len = EXTRACT_BUFFER_LEN;

    buffer = xmalloc(len);

    while (1) {
        sz_in = read_data(a, buffer, len, &eof);
        if (eof) {
            free(buffer);
            return 0;
        }
        if (sz_in == 0)
            goto err_cleanup;

        /* Now write data to the output stream. */
        sz_out = fwrite(buffer, 1, sz_in, stream);
        if (sz_out < sz_in) {
            opkg_msg(ERROR, "Failed to write data to stream: %s\n",
                     strerror(errno));
            goto err_cleanup;
        }
    }

 err_cleanup:
    free(buffer);
    return -1;
}

/* Join left and right path components without intervening '/' as left may end
 * with a prefix to be applied to the names of extracted files.
 *
 * The right path component is stripped of leading '/' or './' components. If
 * the right path component is simply '.' after stripping, it should not be
 * created.
 *
 * Returns the joined path, or NULL if the resulting path should not be created.
 */
static char *join_paths(const char *left, const char *right)
{
    char *path;

    /* Skip leading '/' or './' in right-hand path if present. */
    while (right[0] == '.' && right[1] == '/')
        right += 2;
    while (right[0] == '/')
        right++;

    /* Don't create '.' directory. */
    if (right[0] == '.' && right[1] == '\0')
        return NULL;

    /* Don't extract empty paths. */
    if (right[0] == '\0')
        return NULL;

    if (!left)
        return xstrdup(right);

    sprintf_alloc(&path, "%s%s", left, right);
    return path;
}

/* Transform the destination path of the given entry.
 *
 * Returns 0 on success, 1 where the file does not need to be extracted and <0
 * on error.
 */
static int transform_dest_path(struct archive_entry *entry, const char *dest)
{
    char *path;
    const char *filename;

    filename = archive_entry_pathname(entry);

    path = join_paths(dest, filename);
    if (!path)
        return 1;

    archive_entry_set_pathname(entry, path);
    free(path);

    return 0;
}

/* Transform all path components of the given entry. This includes hardlink and
 * symlink paths as well as the destination path.
 *
 * Returns 0 on success, 1 where the file does not need to be extracted and <0
 * on error.
 */
static int transform_all_paths(struct archive_entry *entry, const char *dest)
{
    char *path;
    const char *filename;
    int r;

    r = transform_dest_path(entry, dest);
    if (r)
        return r;

    /* Next transform hardlink and symlink destinations. */
    filename = archive_entry_hardlink(entry);
    if (filename) {
        /* Apply the same transform to the hardlink path as was applied
         * to the destination path.
         */
        path = join_paths(dest, filename);
        if (!path) {
            opkg_msg(ERROR, "Not extracting '%s': Hardlink to nowhere.\n",
                     archive_entry_pathname(entry));
            return 1;
        }

        archive_entry_set_hardlink(entry, path);
        free(path);
    }

    /* Currently no transform to perform for symlinks. */

    return 0;
}

/* Read a header from the given archive object and handle all possible outcomes.
 * The returned pointer is managed by libarchive and should not be freed by the
 * caller.
 *
 * If the caller needs to know whether EOF was hit without an error, they can
 * pass an eof pointer which will be set to 1 in this case or 0 otherwise.
 */
static struct archive_entry *read_header(struct archive *ar, int *eof)
{
    struct archive_entry *entry;
    int r;
    int retries = 0;

    if (eof)
        *eof = 0;

 retry:
    r = archive_read_next_header(ar, &entry);
    switch (r) {
    case ARCHIVE_OK:
        break;

    case ARCHIVE_WARN:
        opkg_msg(NOTICE, "Warning when reading ar archive header: %s\n",
                 archive_error_string(ar));
        break;

    case ARCHIVE_EOF:
        if (eof)
            *eof = 1;
        return NULL;

    case ARCHIVE_RETRY:
        opkg_msg(ERROR, "Failed to read archive header: %s\n",
                 archive_error_string(ar));
        if (retries++ < 3)
            goto retry;
        else
            return NULL;

    default:
        opkg_msg(ERROR, "Failed to read archive header: %s\n",
                 archive_error_string(ar));
        return NULL;
    }

    return entry;
}

/* Extact a single file from an open archive, writing data to an open stream.
 * Returns 0 on success or <0 on error.
 */
static int extract_file_to_stream(struct archive *a, const char *name,
                                  FILE * stream)
{
    struct archive_entry *entry;
    const char *path;

    while (1) {
        entry = read_header(a, NULL);
        if (!entry)
            return -1;

        /* Cleanup the path of the entry incase it starts with './' or
         * other prefixes.
         *
         * We ignore the return value of transform_dest_path as bad
         * paths simply won't match the requested path name.
         */
        transform_dest_path(entry, NULL);

        path = archive_entry_pathname(entry);
        if (strcmp(path, name) == 0)
            /* We found the requested file. */
            return copy_to_stream(a, stream);
    }
}

/* Extact the paths of files contained in an open archive, writing data to an
 * open stream.  Returns 0 on success or <0 on error.
 */
static int extract_paths_to_stream(struct archive *a, FILE * stream)
{
    struct archive_entry *entry;
    int r;
    const char *path;
    int eof;

    while (1) {
        entry = read_header(a, &eof);
        if (eof)
            return 0;
        if (!entry)
            return -1;

        path = archive_entry_pathname(entry);
        r = fprintf(stream, "%s\n", path);
        if (r <= 0) {
            opkg_msg(ERROR, "Failed to path to stream: %s\n", strerror(errno));
            return -1;
        }
    }
}

static struct archive *open_disk(int flags)
{
    struct archive *disk;
    int r;

    disk = archive_write_disk_new();
    if (!disk) {
        opkg_msg(ERROR, "Failed to create disk archive object.\n");
        return NULL;
    }

    r = archive_write_disk_set_options(disk, flags);
    if (r == ARCHIVE_WARN)
        opkg_msg(NOTICE, "Warning when setting disk options: %s\n",
                 archive_error_string(disk));
    else if (r != ARCHIVE_OK) {
        opkg_msg(ERROR, "Failed to set disk options: %s\n",
                 archive_error_string(disk));
        goto err_cleanup;
    }

    r = archive_write_disk_set_standard_lookup(disk);
    if (r == ARCHIVE_WARN)
        opkg_msg(NOTICE,
                 "Warning when setting user/group lookup functions: %s\n",
                 archive_error_string(disk));
    else if (r != ARCHIVE_OK) {
        opkg_msg(ERROR, "Failed to set user/group lookup functions: %s\n",
                 archive_error_string(disk));
        goto err_cleanup;
    }

    return disk;

 err_cleanup:
    archive_write_free(disk);
    return NULL;
}

/* Print destination paths at DEBUG level. */
static void print_paths(struct archive_entry *entry)
{
    const char *path = archive_entry_pathname(entry);
    const char *hardlink = archive_entry_hardlink(entry);
    const char *symlink = archive_entry_symlink(entry);
    if (hardlink)
        opkg_msg(DEBUG, "Extracting '%s', hardlink to '%s'.\n", path, hardlink);
    else if (symlink)
        opkg_msg(DEBUG, "Extracting '%s', symlink to '%s'.\n", path, symlink);
    else
        opkg_msg(DEBUG, "Extracting '%s'.\n", path);

}

/* Extract an entry to disk, returns 0 on success or <0 on error. */
static int extract_entry(struct archive *a, struct archive_entry *entry,
                         struct archive *disk)
{
    int r;
    int retries = 0;

 retry:
    r = archive_read_extract2(a, entry, disk);
    switch (r) {
    case ARCHIVE_OK:
        break;

    case ARCHIVE_WARN:
        opkg_msg(NOTICE, "Warning when extracting archive entry: %s\n",
                 archive_error_string(a));
        break;

    case ARCHIVE_RETRY:
        opkg_msg(ERROR, "Failed to extract archive entry '%s': %s\n",
                 archive_entry_pathname(entry), archive_error_string(a));
        if (retries++ < 3) {
            opkg_msg(NOTICE, "Retrying...\n");
            goto retry;
        } else
            return -1;

    default:
        opkg_msg(ERROR, "Failed to extract archive entry '%s': %s\n",
                 archive_entry_pathname(entry), archive_error_string(a));
        return -1;
    }

    return 0;
}

/* Extract all files in an archive to the filesystem under the path given by
 * dest. Returns 0 on success or <0 on error.
 */
static int extract_all(struct archive *a, const char *dest, int flags)
{
    struct archive *disk;
    struct archive_entry *entry;
    int r;
    int eof;

    disk = open_disk(flags);
    if (!disk)
        return -1;

    while (1) {
        entry = read_header(a, &eof);
        if (eof)
            break;
        if (!entry) {
            r = -1;
            goto err_cleanup;
        }

        r = transform_all_paths(entry, dest);
        if (r == 1)
            continue;
        if (r < 0) {
            opkg_msg(ERROR, "Failed to transform path.\n");
            goto err_cleanup;
        }

        print_paths(entry);

        r = extract_entry(a, entry, disk);
        if (r < 0)
            goto err_cleanup;
    }

    r = ARCHIVE_OK;
 err_cleanup:
    archive_write_free(disk);
    return (r == ARCHIVE_OK) ? 0 : -1;
}

/* Open an outer archive with the given filename. */
static struct archive *open_outer(const char *filename)
{
    struct archive *outer;
    int r;

    outer = archive_read_new();
    if (!outer) {
        opkg_msg(ERROR, "Failed to create outer archive object.\n");
        return NULL;
    }

    /* Outer package is in 'ar' format, uncompressed. */
    r = archive_read_support_format_ar(outer);
    if (r != ARCHIVE_OK) {
        opkg_msg(ERROR, "Ar format not supported: %s\n",
                 archive_error_string(outer));
        goto err_cleanup;
    }

    r = archive_read_open_filename(outer, filename, EXTRACT_BUFFER_LEN);
    if (r != ARCHIVE_OK) {
        opkg_msg(ERROR, "Failed to open package '%s': %s\n", filename,
                 archive_error_string(outer));
        goto err_cleanup;
    }

    return outer;

 err_cleanup:
    archive_read_free(outer);
    return NULL;
}

/* Open an inner archive at the current position within the given outer archive. */
static struct archive *open_inner(struct archive *outer)
{
    struct archive *inner;
    struct inner_data *data;
    int r;

    inner = archive_read_new();
    if (!inner) {
        opkg_msg(ERROR, "Failed to create inner archive object.\n");
        return NULL;
    }

    data = (struct inner_data *)xmalloc(sizeof(struct inner_data));
    data->buffer = xmalloc(EXTRACT_BUFFER_LEN);
    data->outer = outer;

    /* Inner package is in 'tar' format, gzip compressed. */
    r = archive_read_support_filter_gzip(inner);
    if (r == ARCHIVE_WARN) {
        /* libarchive returns ARCHIVE_WARN if the filter is provided by
         * an external program.
         */
        opkg_msg(INFO, "Gzip support provided by external program.\n");
    } else if (r != ARCHIVE_OK) {
        opkg_msg(ERROR, "Gzip format not supported.\n");
        goto err_cleanup;
    }

    r = archive_read_support_format_tar(inner);
    if (r != ARCHIVE_OK) {
        opkg_msg(ERROR, "Tar format not supported: %s\n",
                 archive_error_string(outer));
        goto err_cleanup;
    }

    r = archive_read_open(inner, data, NULL, inner_read, inner_close);
    if (r != ARCHIVE_OK) {
        opkg_msg(ERROR, "Failed to open inner archive: %s\n",
                 archive_error_string(inner));
        goto err_cleanup;
    }

    return inner;

 err_cleanup:
    archive_read_free(inner);
    free(data->buffer);
    free(data);
    return NULL;
}

/* Locate an inner archive with the given name in the given outer archive.
 * Returns 0 if the item was found, <0 otherwise.
 */
static int find_inner(struct archive *outer, const char *arname)
{
    const char *path;
    struct archive_entry *entry;

    while (1) {
        entry = read_header(outer, NULL);
        if (!entry)
            return -1;

        /* Cleanup the path of the entry incase it starts with './' or
         * other prefixes.
         *
         * We ignore the return value of transform_dest_path as bad
         * paths simply won't match the requested path name.
         */
        transform_dest_path(entry, NULL);

        path = archive_entry_pathname(entry);
        if (strcmp(path, arname) == 0) {
            /* We found the requested file. */
            return 0;
        }
    }
}

/* Prepare to extract 'control.tar.gz' or 'data.tar.gz' from the outer package
 * archive, returning a `struct archive *` for the enclosed file. On error,
 * return NULL.
 */
static struct archive *extract_outer(const char *filename, const char *arname)
{
    int r;
    struct archive *inner;
    struct archive *outer;

    outer = open_outer(filename);
    if (!outer)
        return NULL;

    r = find_inner(outer, arname);
    if (r < 0)
        goto err_cleanup;

    inner = open_inner(outer);
    if (!inner)
        goto err_cleanup;

    return inner;

 err_cleanup:
    archive_read_free(outer);
    return NULL;
}

static struct archive *open_compressed_file(const char *filename)
{
    struct archive *ar;
    int r;

    ar = archive_read_new();
    if (!ar) {
        opkg_msg(ERROR,
                 "Failed to create archive object for compressed file.\n");
        return NULL;
    }

    /* Support raw data in gzip compression format. */
    r = archive_read_support_filter_gzip(ar);
    if (r == ARCHIVE_WARN) {
        /* libarchive returns ARCHIVE_WARN if the filter is provided by
         * an external program.
         */
        opkg_msg(INFO, "Gzip support provided by external program.\n");
    } else if (r != ARCHIVE_OK) {
        opkg_msg(ERROR, "Gzip format not supported: %s\n",
                 archive_error_string(ar));
        goto err_cleanup;
    }

    r = archive_read_support_format_raw(ar);
    if (r != ARCHIVE_OK) {
        opkg_msg(ERROR, "Raw format not supported: %s\n",
                 archive_error_string(ar));
        goto err_cleanup;
    }

    /* Open input file and prepare for reading. */
    r = archive_read_open_filename(ar, filename, EXTRACT_BUFFER_LEN);
    if (r != ARCHIVE_OK) {
        opkg_msg(ERROR, "Failed to open compressed file '%s': %s\n", filename,
                 archive_error_string(ar));
        goto err_cleanup;
    }

    return ar;

 err_cleanup:
    archive_read_free(ar);
    return NULL;
}

/*******************************************************************************
 * Glue layer.
 */

struct opkg_ar *ar_open_pkg_control_archive(const char *filename)
{
    struct opkg_ar *ar;

    ar = (struct opkg_ar *)xmalloc(sizeof(struct opkg_ar));

    ar->ar = extract_outer(filename, "control.tar.gz");
    if (!ar->ar) {
        free(ar);
        return NULL;
    }

    /* We don't want to set ownership and permissions of control files
     * incase they're incorrect in the archive. They should instead be owned
     * by the user who ran opkg (usually root) and given permissions
     * according to the current umask.
     */
    ar->extract_flags = 0;

    return ar;
}

struct opkg_ar *ar_open_pkg_data_archive(const char *filename)
{
    struct opkg_ar *ar;

    ar = (struct opkg_ar *)xmalloc(sizeof(struct opkg_ar));

    ar->ar = extract_outer(filename, "data.tar.gz");
    if (!ar->ar) {
        free(ar);
        return NULL;
    }

    /** Flags:
     *
     * TODO: Do we want to support ACLs, extended flags and extended
     * attributes? (ARCHIVE_EXTRACT_ACL, ARCHIVE_EXTRACT_FFLAGS,
     * ARCHIVE_EXTRACT_XATTR).
     */
    ar->extract_flags = ARCHIVE_EXTRACT_OWNER | ARCHIVE_EXTRACT_PERM |
        ARCHIVE_EXTRACT_TIME | ARCHIVE_EXTRACT_UNLINK;

    return ar;
}

struct opkg_ar *ar_open_compressed_file(const char *filename)
{
    struct opkg_ar *ar;
    struct archive_entry *entry;

    ar = (struct opkg_ar *)xmalloc(sizeof(struct opkg_ar));

    ar->ar = open_compressed_file(filename);
    if (!ar->ar)
        goto err_cleanup;

    /* Flags aren't used when handling compressed files. */
    ar->extract_flags = 0;

    /* As ar represents a single compressed file it should just have one
     * header. We skip over this header here so that the caller doesn't need
     * to know about it.
     */
    entry = read_header(ar->ar, NULL);
    if (!entry)
        goto err_cleanup;

    return ar;

 err_cleanup:
    if (ar->ar)
        archive_read_free(ar->ar);
    free(ar);

    return NULL;
}

int ar_copy_to_stream(struct opkg_ar *ar, FILE * stream)
{
    return copy_to_stream(ar->ar, stream);
}

int ar_extract_file_to_stream(struct opkg_ar *ar, const char *filename,
                              FILE * stream)
{
    return extract_file_to_stream(ar->ar, filename, stream);
}

int ar_extract_paths_to_stream(struct opkg_ar *ar, FILE * stream)
{
    return extract_paths_to_stream(ar->ar, stream);
}

int ar_extract_all(struct opkg_ar *ar, const char *prefix)
{
    return extract_all(ar->ar, prefix, ar->extract_flags);
}

void ar_close(struct opkg_ar *ar)
{
    archive_read_free(ar->ar);
    free(ar);
}