#!/usr/bin/env python3

from __future__ import print_function

import argparse
import codecs
import math
import operator
import os
import sys
from subprocess import Popen, PIPE
from tempfile import mkstemp


def check_sparse(filename):
    magic = 3978755898
    with open(filename, 'rb') as i:
        word = i.read(4)
        if magic == int(codecs.encode(word[::-1], 'hex'), 16):
            return True
    return False


def shell_command(comm_list):
    command = Popen(comm_list, stdout=PIPE, stderr=PIPE)
    command.communicate()
    command.wait()
    if command.returncode != 0:
        sys.exit(1)


def parse_input(input_file):
    parsed_lines = list()
    lines = input_file.readlines()
    for line in lines:
        line = line.strip()
        if not line or line[0] == "#":
            continue
        params = line.split()
        if len(params) == 3:
            for param in params:
                # interprete file paths such as $OUT/system.img
                param = os.path.expandvars(param)
            parsed_lines.append(params)

    partitions = list()
    num_used = set()
    for line in parsed_lines:
        partition_info = dict()
        partition_info["path"] = line[0]
        partition_info["label"] = line[1]
        # round up by 1M
        sizeByMb = str(math.ceil(os.path.getsize(line[0]) / 1024 / 1024))
        partition_info["sizeByMb"] = sizeByMb

        try:
            partition_info["num"] = int(line[2])
        except ValueError:
            print("'%s' cannot be converted to int" % (line[2]))
            sys.exit(1)

        # check if the partition number is out of range
        if partition_info["num"] > len(lines) or partition_info["num"] < 0:
            print("Invalid partition number: %d, range [1..%d]" % \
                  (partition_info["num"], len(lines)))
            sys.exit(1)

        # check if the partition number is duplicated
        if partition_info["num"] in num_used:
            print("Duplicated partition number:%d" % (partition_info["num"]))
            sys.exit(1)
        num_used.add(partition_info["num"])
        partitions.append(partition_info)

    partitions.sort(key=operator.itemgetter("num"))
    return partitions


def write_partition(partition, output_file, offset):
    # $ dd if=/path/to/image of=/path/to/output conv=notrunc,sync \
    #   ibs=1024k obs=1024k seek=<offset>
    dd_comm = ['dd', 'if=' + partition["path"], 'of=' + output_file, 'conv=notrunc,sync',
               'ibs=1024k', 'obs=1024k', 'seek=' + str(offset)]
    shell_command(dd_comm)
    return


def unsparse_partition(partition):
    # if the input image is in sparse format, unsparse it
    simg2img = os.environ.get('SIMG2IMG', 'simg2img')
    print("Unsparsing %s" % (partition["path"]), end=' ')
    partition["fd"], temp_file = mkstemp()
    shell_command([simg2img, partition["path"], temp_file])
    partition["path"] = temp_file
    print("Done")
    return


def clear_partition_table(filename):
    sgdisk = os.environ.get('SGDISK', 'sgdisk')
    print("%s --clear %s" % (sgdisk, filename))
    shell_command([sgdisk, '--clear', filename])
    return


def add_partition(partition, output_file):
    sgdisk = os.environ.get('SGDISK', 'sgdisk')
    num = str(partition["num"])
    new_comm = '--new=' + num + ':' + partition["start"] + ':' + partition["end"]
    type_comm = '--type=' + num + ':8300'
    name_comm = '--change-name=' + num + ':' + partition["label"]
    # build partition table in order. for example:
    # $ sgdisk --new=1:2048:5244927 --type=1:8300 --change-name=1:system \
    #   /path/to/output
    shell_command([sgdisk, new_comm, type_comm, name_comm, output_file])
    return


def main():
    # check usage:
    parser = argparse.ArgumentParser()
    parser.add_argument("-i", "--input",
                        type=str, help="input configuration file",
                        default="image_config")
    parser.add_argument("-o", "--output",
                        type=str, help="output filename",
                        default=os.environ.get("OUT", ".") + "/combined.img")
    args = parser.parse_args()

    output_filename = os.path.expandvars(args.output)

    # remove the output_filename.qcow2
    print("removing " + output_filename + ".qcow2")
    shell_command(['rm', '-rf', output_filename + ".qcow2"])

    # check input file
    config_filename = args.input
    if not os.path.exists(config_filename):
        print("Invalid config file name " + config_filename)
        sys.exit(1)

    # read input file
    config = open(config_filename, "r")
    partitions = parse_input(config)
    config.close()

    # take a shortcut in build environment
    if os.path.exists(output_filename) and len(partitions) == 2:
        print("updating " + output_filename + " ...")
        shell_command(['dd', "if=" + partitions[0]["path"], "of=" + output_filename,
                       "conv=notrunc,sync", "ibs=1024k", "obs=1024k", "seek=1"])
        shell_command(['dd', "if=" + partitions[1]["path"], "of=" + output_filename,
                       "conv=notrunc,sync", "ibs=1024k", "obs=1024k", "seek=2"])
        print("done")
        sys.exit(0)
    elif len(partitions) == 2:
        gptprefix = partitions[0]["sizeByMb"] + "_" + partitions[1]["sizeByMb"]
        prebuilt_gpt_dir = os.path.dirname(os.path.abspath( __file__ )) + "/prebuilt/gpt/" + gptprefix
        gpt_head = prebuilt_gpt_dir + "/head.img"
        gpt_tail = prebuilt_gpt_dir + "/head.img"
        if os.path.exists(gpt_head) and os.path.exists(gpt_tail):
            print("found prebuilt gpt header and footer, use it")
            shell_command(['dd', "if=" + gpt_head, "of=" + output_filename, "bs=1024k",
                    "conv=notrunc,sync", "count=1"])
            shell_command(['dd', "if=" + partitions[0]["path"], "of=" + output_filename,
                    "bs=1024k", "conv=notrunc,sync", "seek=1"])
            shell_command(['dd', "if=" + partitions[1]["path"], "of=" + output_filename,
                    "bs=1024k", "conv=notrunc,sync", "seek=" + str(1 + int(partitions[0]["sizeByMb"]))])
            shell_command(['dd', "if=" + gpt_tail, "of=" + output_filename,
                    "bs=1024k", "conv=notrunc,sync",
                    "seek=" + str(1 + int(partitions[0]["sizeByMb"]) + int(partitions[1]["sizeByMb"]))])
            print("done")
            sys.exit(0)

    # combine the images
    # add padding
    shell_command(['dd', 'if=/dev/zero', 'of=' + output_filename, 'ibs=1024k', 'count=1'])

    for partition in partitions:
        offset = os.path.getsize(output_filename)
        partition["start"] = str(offset // 512)
        # dectect sparse file format
        if check_sparse(partition["path"]):
            unsparse_partition(partition)

        # TODO: extract the partition if the image file is already formatted

        write_partition(partition, output_filename, offset // 1024 // 1024)
        offset = os.path.getsize(output_filename)
        partition["end"] = str(offset // 512 - 1)

    # add padding
    # $ dd if=/dev/zero of=/path/to/output conv=notrunc bs=1 \
    #   count=1024k seek=<offset>
    offset = os.path.getsize(output_filename) // 1024 // 1024
    shell_command(['dd', 'if=/dev/zero', 'of=' + output_filename,
                   'conv=notrunc', 'bs=1024k', 'count=1', 'seek=' + str(offset)])

    # make partition table
    # $ sgdisk --clear /path/to/output
    clear_partition_table(output_filename)

    for partition in partitions:
        add_partition(partition, output_filename)
        # clean up, delete any unsparsed image files generated
        if 'fd' in partition:
            os.close(partition["fd"])
            os.remove(partition["path"])


if __name__ == "__main__":
    main()