#!/usr/bin/env python3
import math

pageSize = 128
sectorsPerTrack = 256
blockSize = 16384
pagesPerBlock = 128
maxDirs = 128
dirBlocks = 1


def addBootloader(name):
    loader = open(name, 'rb')
    b = loader.read()

    if len(b) > pageSize:
        raise RuntimeError("Bootloader binary cannot be larger than one page")

    out.seek(0)
    out.write(b)

def addOS(cpmName, biosName):
    cpm = open(cpmName, 'rb')
    bios = open(biosName, 'rb')

    b = cpm.read()
    out.seek(pageSize)
    out.write(b)

    b = bios.read()
    out.seek(pageSize + 0x1600)
    out.write(b)

def seekBlock(i):
    # Blocks start at track 1, sector 0
    out.seek(pageSize*sectorsPerTrack + i*blockSize)

def initDirs():
    seekBlock(0)
    out.write(bytearray(([0xe5] + [0x00] * 31) * maxDirs))

fileCounter = 0
allocationCounter = 1
def addFile(filename, n, t):
    global fileCounter
    global allocationCounter

    if fileCounter > maxDirs:
        raise RuntimeError("Max dir entries has been reached")

    if len(n) > 8:
        raise RuntimeError("Filename cannot be longer than 8")

    if len(t) > 3:
        raise RuntimeError("Filetype cannot be longer than 3")

    f = open(filename, 'rb')
    b = f.read()

    total_records = math.ceil(len(b)/pageSize)
    records = (total_records - 1) % pagesPerBlock + 1
    extends = math.ceil(total_records/pagesPerBlock)

    if extends >= 8:
        RuntimeError("File is to big to be stored in one entry, multple entries are not implemented")

    seekBlock(0)
    out.seek(32*fileCounter, 1)

    # Write user (assume 0 for now)
    out.write(bytearray(1))

    # Write the name
    out.write(n.upper().encode("ascii"))
    out.write((" " * (8-len(n))).encode("ascii"))

    # Write the type
    out.write(t.upper().encode("ascii"))
    out.write((" " * (3-len(t))).encode("ascii"))

    # Write extend
    # @todo This is actually wrong, as the order is EX S1 S2 with S1 being unused, however we never deal with files that big
    out.write((extends-1).to_bytes(1, byteorder='little'))

    # Reserved byte
    out.write(bytearray(2))

    # Number of records

    out.write(records.to_bytes(1, byteorder='little'))

    allocationCounterOld = allocationCounter
    # We are assuming one block per file for now, so we can use fileCounter
    for i in range(extends):
        out.write(allocationCounter.to_bytes(2, byteorder='little'))
        allocationCounter += 1

    seekBlock(allocationCounterOld)
    out.write(b)

    fileCounter += 1


def main():
    # @todo Load the config from a file that we specify instead of hardcoding everything
    # We can probably keep the os part hardcoded as that is not something we really need to change between different projects
    global out
    out = open('disk.img', 'wb')

    addBootloader('../../software/loader/.build/loader.bin')
    addOS('../../software/cpm/.build/cpm22.bin', '../../software/cpm/.build/bios.bin')

    initDirs()

    addFile("../../software/monitor/.build/MONITOR.COM", "MONITOR", "COM")
    addFile("../../software/tetris/.build/tetris.com", "TETRIS", "COM")
    addFile("bin/STAT.COM", "STAT", "COM")
    addFile("bin/MBASIC.COM", "MBASIC", "COM")

if __name__ == "__main__":
    main()