"""Build an instance as a static site suitable for serving via e.g. Nginx.

SPDX-FileCopyrightText: © 2022 Brian S. Stephan <bss@incorporeal.org>
SPDX-License-Identifier: AGPL-3.0-or-later
"""
import argparse
import os
import shutil
import stat
import tempfile

from termcolor import cprint

from incorporealcms import init_instance
from incorporealcms.pages import handle_markdown_file_path


def build():
    """Build the static site generated against an instance directory."""
    parser = argparse.ArgumentParser(
        description="Build the static site generated against an instance directory.",
    )
    parser.add_argument(
        'instance_dir', help="path to instance directory root (NOTE: the program will go into pages/)"
    )
    parser.add_argument(
        'output_dir', help="path to directory to output to (NOTE: the program must be able to write into its parent!)"
    )
    args = parser.parse_args()

    # check output path before doing work
    if not os.path.isdir(args.output_dir):
        # if it doesn't exist, great, we'll just move the temporary dir later;
        # if it exists and is a dir, that's fine, but if it's a file, we should error
        if os.path.exists(args.output_dir):
            raise ValueError(f"specified output path '{args.output_dir}' exists as a file!")

    output_dir = os.path.abspath(args.output_dir)
    instance_dir = os.path.abspath(args.instance_dir)
    pages_dir = os.path.join(instance_dir, 'pages')

    # initialize configuration with the path to the instance
    init_instance(instance_dir)

    # putting the temporary directory next to the desired output so we can safely rename it later
    tmp_output_dir = tempfile.mkdtemp(dir=os.path.dirname(output_dir))
    cprint(f"creating temporary directory '{tmp_output_dir}' for writing", 'green')

    # CORE CONTENT
    # render and/or copy into the output dir after changing into the instance dir (to simplify paths)
    os.chdir(pages_dir)
    for base_dir, subdirs, files in os.walk(pages_dir):
        # remove the absolute path of the pages directory from the base_dir
        base_dir = os.path.relpath(base_dir, pages_dir)
        # create subdirs seen here for subsequent depth
        for subdir in subdirs:
            dst = os.path.join(tmp_output_dir, base_dir, subdir)
            if os.path.islink(os.path.join(base_dir, subdir)):
                # keep the link relative to the output directory
                src = symlink_to_relative_dest(pages_dir, os.path.join(base_dir, subdir))
                print(f"creating directory symlink '{dst}' -> '{src}'")
                os.symlink(src, dst, target_is_directory=True)
            else:
                print(f"creating directory '{dst}'")
                os.mkdir(dst)

        # process and copy files
        for file_ in files:
            dst = os.path.join(tmp_output_dir, base_dir, file_)
            if os.path.islink(os.path.join(base_dir, file_)):
                # keep the link relative to the output directory
                src = symlink_to_relative_dest(pages_dir, os.path.join(base_dir, file_))
                print(f"creating symlink '{dst}' -> '{src}'")
                os.symlink(src, dst, target_is_directory=False)
            else:
                src = os.path.join(base_dir, file_)
                print(f"copying file '{src}' -> '{dst}'")
                shutil.copy2(src, dst)

                # render markdown as HTML
                if src.endswith('.md'):
                    rendered_file = dst.removesuffix('.md') + '.html'
                    try:
                        content = handle_markdown_file_path(src)
                    except UnicodeDecodeError:
                        # perhaps this isn't a markdown file at all for some reason; we
                        # copied it above so stick with tha
                        cprint(f"{src} has invalid bytes! skipping", 'yellow')
                        continue
                    with open(rendered_file, 'w') as dst_file:
                        dst_file.write(content)

    # TODO: STATIC DIR

    # move temporary dir to the destination
    old_output_dir = f'{output_dir}-old-{os.path.basename(tmp_output_dir)}'
    if os.path.exists(output_dir):
        cprint(f"renaming '{output_dir}' to '{old_output_dir}'", 'green')
        os.rename(output_dir, old_output_dir)
    cprint(f"renaming '{tmp_output_dir}' to '{output_dir}'", 'green')
    os.rename(tmp_output_dir, output_dir)
    os.chmod(output_dir,
             stat.S_IWUSR | stat.S_IRUSR | stat.S_IRGRP | stat.S_IROTH | stat.S_IXUSR | stat.S_IXGRP | stat.S_IXOTH)

    # TODO: unlink old dir above? arg flag?


def symlink_to_relative_dest(base_dir: str, source: str) -> str:
    """Given a symlink, make sure it points to something inside the instance and provide its real destination.

    Args:
        base_dir: the full absolute path of the instance's pages dir, which the symlink destination must be in.
        source: the symlink to check
    Returns:
        what the symlink points at
    """
    if not os.path.realpath(source).startswith(base_dir):
        raise ValueError(f"symlink destination {os.path.realpath(source)} is outside the instance!")
    # this symlink points to realpath inside base_dir, so relative to base_dir, the symlink dest is...
    return os.path.relpath(os.path.realpath(source), base_dir)