mylastool.py

"""My tool for working with LAS files in an azure storage container."""

import os
import sys
import azure.storage.blob


def get_container_url():
    """Get url for a container."""
    return os.environ['CONTAINER_URL']


def get_container_from_url(url):
    """Create container from a url."""
    return azure.storage.blob.ContainerClient.from_container_url(url)


def get_list_of_lasfiles(container):
    """Get list of LAS files in a container."""
    files = []
    for blob in container.list_blobs():
        if blob.name.upper().endswith('.LAS'):
            files.append(blob.name)
    return files


def print_list_of_lasfiles(container):
    """Print pretty directory listing LAS file in container."""
    files = get_list_of_lasfiles(container)
    for name in files:
        print(name)


def read_lasfile(container, filename):
    """Read given LAS file from container."""
    if not filename.upper().endswith('.LAS'):
        raise OSError("Probably not a LAS file")
    blob_client = container.get_blob_client(filename)
    data = blob_client.download_blob().content_as_bytes()
    lines = []
    for line in data.splitlines():
        lines.append(line.decode("ascii", errors='ignore'))
    return lines


def find_section_index(lines, prefix):
    """Find index of first line with given prefix."""
    for index, line in enumerate(lines):
        if line.strip().startswith(prefix):
            return index
    raise ValueError


def get_header_section(lines):
    """Return the lines for the header section."""
    return lines[:find_section_index(lines, '~A')]


def get_data_section(lines):
    """Return the lines for the data section."""
    return lines[find_section_index(lines, '~A')+1:]


def get_curve_section(lines):
    """Return the lines for the curve section."""
    start_idx = find_section_index(lines, '~C')
    end_idx = find_section_index(lines[start_idx+1:], '~')
    return lines[start_idx+1:start_idx+1+end_idx]


def get_curve_mnemonics(lines):
    """Get a list of curve names."""
    names = []
    for line in get_curve_section(lines):
        if line.strip().startswith("#"):
            continue
        curvename = line.split('.')[0].strip()
        names.append(curvename)
    return names

def print_header_section(lines):
    """Print the header section."""
    for line in get_header_section(lines):
        print(line)


def print_data_section(lines):
    """Print the data section."""
    for line in get_data_section(lines):
        print(line)


def print_curve_mnemonics(lines):
    """Pretty print the curve names."""
    print(*get_curve_mnemonics(lines), sep=' | ')


def print_helpmessage():
    """Print help message."""
    print("usage: mylastool.py <command> [file]")
    print("examples:")
    print("    python mylastool.py list")
    print("    python mylastool.py header A/B/C.LAS")
    print("    python mylastool.py data   A/B/C.LAS")
    print("    python mylastool.py curves A/B/C.LAS")
    print("also, remember to set CONTAINER_URL")



def main(argv):
    """Parse a list of arguments and do magic."""
    if len(argv) < 2:
        print_helpmessage()
        return 1

    command = argv[1]

    if command not in ('list', 'header', 'data', 'curves'):
        print('error: unknown command')
        print_helpmessage()
        return 1

    url = get_container_url()
    container = get_container_from_url(url)

    if command == 'list':
        print_list_of_lasfiles(container)
        return 0

    if len(argv) < 3:
        print('error: expected a filename')
        print_helpmessage()
        return 1

    lasfile = argv[2]
    lines = read_lasfile(container, lasfile)

    if command == 'header':
        print_header_section(lines)
        return 0

    if command == 'data':
        print_data_section(lines)
        return 0

    if command == 'curves':
        print_curve_mnemonics(lines)
        return 0

    print('Huh?')
    print_helpmessage()
    return 1


if __name__ == '__main__':
    sys.exit(main(sys.argv))

# References:
# https://www.cwls.org/wp-content/uploads/2017/02/Las2_Update_Feb2017.pdf
# https://docs.microsoft.com/en-us/python/api/azure-storage-blob/?view=azure-python