import os
import re
import shutil
from pathlib import Path
from typing import Any, Dict, Optional

import httpx
import typer
from wasabi import msg

from ..util import SimpleFrozenDict, download_file, ensure_path, get_checksum
from ..util import get_git_version, git_checkout, load_project_config
from ..util import parse_config_overrides, working_dir
from .main import PROJECT_FILE, Arg, Opt, app

# Whether assets are extra if `extra` is not set.
EXTRA_DEFAULT = False


@app.command(
    "assets",
    context_settings={"allow_extra_args": True, "ignore_unknown_options": True},
)
def project_assets_cli(
    # fmt: off
    ctx: typer.Context,  # This is only used to read additional arguments
    project_dir: Path = Arg(Path.cwd(), help="Path to cloned project. Defaults to current working directory.", exists=True, file_okay=False),
    sparse_checkout: bool = Opt(False, "--sparse", "-S", help="Use sparse checkout for assets provided via Git, to only check out and clone the files needed. Requires Git v22.2+."),
    extra: bool = Opt(False, "--extra", "-e", help="Download all assets, including those marked as 'extra'.")
    # fmt: on
):
    """Fetch project assets like datasets and pretrained weights. Assets are
    defined in the "assets" section of the project.yml. If a checksum is
    provided in the project.yml, the file is only downloaded if no local file
    with the same checksum exists.

    DOCS: https://github.com/explosion/weasel/tree/main/docs/tutorial/directory-and-assets.md
    """
    overrides = parse_config_overrides(ctx.args)
    project_assets(
        project_dir,
        overrides=overrides,
        sparse_checkout=sparse_checkout,
        extra=extra,
    )


def project_assets(
    project_dir: Path,
    *,
    overrides: Dict[str, Any] = SimpleFrozenDict(),
    sparse_checkout: bool = False,
    extra: bool = False,
) -> None:
    """Fetch assets for a project using DVC if possible.

    project_dir (Path): Path to project directory.
    sparse_checkout (bool): Use sparse checkout for assets provided via Git, to only check out and clone the files
                            needed.
    extra (bool): Whether to download all assets, including those marked as 'extra'.
    """
    project_path = ensure_path(project_dir)
    config = load_project_config(project_path, overrides=overrides)
    assets = [
        asset
        for asset in config.get("assets", [])
        if extra or not asset.get("extra", EXTRA_DEFAULT)
    ]
    if not assets:
        msg.warn(
            f"No assets specified in {PROJECT_FILE} (if assets are marked as extra, download them with --extra)",
            exits=0,
        )
    msg.info(f"Fetching {len(assets)} asset(s)")

    for asset in assets:
        dest = (project_dir / asset["dest"]).resolve()
        checksum = asset.get("checksum")
        if "git" in asset:
            git_err = (
                "Cloning Weasel project templates requires Git and the 'git' command. "
                "Make sure it's installed and that the executable is available."
            )
            get_git_version(error=git_err)
            if dest.exists():
                # If there's already a file, check for checksum
                if checksum and checksum == get_checksum(dest):
                    msg.good(
                        f"Skipping download with matching checksum: {asset['dest']}"
                    )
                    continue
                else:
                    if dest.is_dir():
                        shutil.rmtree(dest)
                    else:
                        dest.unlink()
            if "repo" not in asset["git"] or asset["git"]["repo"] is None:
                msg.fail(
                    "A git asset must include 'repo', the repository address.", exits=1
                )
            if "path" not in asset["git"] or asset["git"]["path"] is None:
                msg.fail(
                    "A git asset must include 'path' - use \"\" to get the entire repository.",
                    exits=1,
                )
            git_checkout(
                asset["git"]["repo"],
                asset["git"]["path"],
                dest,
                branch=asset["git"].get("branch"),
                sparse=sparse_checkout,
            )
            msg.good(f"Downloaded asset {dest}")
        else:
            url = asset.get("url")
            if not url:
                # project.yml defines asset without URL that the user has to place
                check_private_asset(dest, checksum)
                continue
            fetch_asset(project_path, url, dest, checksum)


def check_private_asset(dest: Path, checksum: Optional[str] = None) -> None:
    """Check and validate assets without a URL (private assets that the user
    has to provide themselves) and give feedback about the checksum.

    dest (Path): Destination path of the asset.
    checksum (Optional[str]): Optional checksum of the expected file.
    """
    if not Path(dest).exists():
        err = f"No URL provided for asset. You need to add this file yourself: {dest}"
        msg.warn(err)
    else:
        if not checksum:
            msg.good(f"Asset already exists: {dest}")
        elif checksum == get_checksum(dest):
            msg.good(f"Asset exists with matching checksum: {dest}")
        else:
            msg.fail(f"Asset available but with incorrect checksum: {dest}")


def fetch_asset(
    project_path: Path, url: str, dest: Path, checksum: Optional[str] = None
) -> None:
    """Fetch an asset from a given URL or path. If a checksum is provided and a
    local file exists, it's only re-downloaded if the checksum doesn't match.

    project_path (Path): Path to project directory.
    url (str): URL or path to asset.
    checksum (Optional[str]): Optional expected checksum of local file.
    RETURNS (Optional[Path]): The path to the fetched asset or None if fetching
        the asset failed.
    """
    dest_path = (project_path / dest).resolve()
    if dest_path.exists():
        # If there's already a file, check for checksum
        if checksum:
            if checksum == get_checksum(dest_path):
                msg.good(f"Skipping download with matching checksum: {dest}")
                return
        else:
            # If there's not a checksum, make sure the file is a possibly valid size
            if os.path.getsize(dest_path) == 0:
                msg.warn(f"Asset exists but with size of 0 bytes, deleting: {dest}")
                os.remove(dest_path)
    # We might as well support the user here and create parent directories in
    # case the asset dir isn't listed as a dir to create in the project.yml
    if not dest_path.parent.exists():
        dest_path.parent.mkdir(parents=True)
    with working_dir(project_path):
        url = convert_asset_url(url)
        try:
            download_file(url, dest_path)
            msg.good(f"Downloaded asset {dest}")
        except httpx.HTTPError as e:
            if Path(url).exists() and Path(url).is_file():
                # If it's a local file, copy to destination
                shutil.copy(url, str(dest_path))
                msg.good(f"Copied local asset {dest}")
            else:
                msg.fail(f"Download failed: {dest}", e)
    if checksum and checksum != get_checksum(dest_path):
        msg.fail(f"Checksum doesn't match value defined in {PROJECT_FILE}: {dest}")


def convert_asset_url(url: str) -> str:
    """Check and convert the asset URL if needed.

    url (str): The asset URL.
    RETURNS (str): The converted URL.
    """
    # If the asset URL is a regular GitHub URL it's likely a mistake
    if (
        re.match(r"(http(s?)):\/\/github.com", url)
        and "releases/download" not in url
        and "/raw/" not in url
    ):
        converted = url.replace("github.com", "raw.githubusercontent.com")
        converted = re.sub(r"/(tree|blob)/", "/", converted)
        msg.warn(
            "Downloading from a regular GitHub URL. This will only download "
            "the source of the page, not the actual file. Converting the URL "
            "to a raw URL.",
            converted,
        )
        return converted
    return url
