import hashlib
import json
import os
from contextlib import contextmanager
from threading import Lock

import fasteners

from conan.errors import ConanException
from conan.internal.util.dates import timestamp_now
from conan.internal.util.files import load, save, remove_if_dirty


class DownloadCache:
    """ The download cache has 3 folders
    - "s": SOURCE_BACKUP for the files.download(internet_url) backup sources feature
    - "c": CONAN_CACHE: for caching Conan packages artifacts
    - "locks": The LOCKS folder containing the file locks for concurrent access to the cache
    """
    _LOCKS = "locks"
    _SOURCE_BACKUP = "s"
    _CONAN_CACHE = "c"

    def __init__(self, path: str):
        self._path: str = path

    def source_path(self, sha256):
        return os.path.join(self._path, self._SOURCE_BACKUP, sha256)

    def cached_path(self, url):
        md = hashlib.sha256()
        md.update(url.encode())
        h = md.hexdigest()
        return os.path.join(self._path, self._CONAN_CACHE, h), h

    _thread_locks = {}  # Needs to be shared among all instances

    @contextmanager
    def lock(self, lock_id):
        lock = os.path.join(self._path, self._LOCKS, lock_id)
        with fasteners.InterProcessLock(lock):  # TODO: Abstract away when necessary for concurrency
            # Once the process has access, make sure multithread is locked too
            # as SimpleLock doesn't work multithread
            thread_lock = self._thread_locks.setdefault(lock, Lock())
            thread_lock.acquire()
            try:
                yield
            finally:
                thread_lock.release()

    def get_backup_sources_files(self, excluded_urls, package_list=None, only_upload=True):
        """Get list of backup source files currently present in the cache,
        either all of them if no package_list is give, or filtered by those belonging to the references in the package_list

        Will exclude the sources that come from URLs present in excluded_urls

        @param excluded_urls: a list of URLs to exclude backup sources files if they come from any of these URLs
        @param package_list: a PackagesList object to filter backup files from (The files should have been downloaded form any of the references in the package_list)
        @param only_upload: if True, only return the files for packages that are set to be uploaded"""
        path_backups = os.path.join(self._path, self._SOURCE_BACKUP)

        if not os.path.exists(path_backups):
            return []

        if excluded_urls is None:
            excluded_urls = []

        def has_excluded_urls(backup_urls):
            return all(any(url.startswith(excluded_url)
                           for excluded_url in excluded_urls)
                       for url in backup_urls)

        def should_upload_sources(package):
            return any(prev.get("upload") for prev in package["revisions"].values())

        all_refs = set()
        if package_list is not None:
            for k, ref in package_list.refs().items():
                packages = ref.get("packages", {}).values()
                if not only_upload or ref.get("upload") or any(should_upload_sources(p) for p in packages):
                    all_refs.add(str(k))

        path_backups_contents = []

        dirty_ext = ".dirty"
        for path in os.listdir(path_backups):
            if remove_if_dirty(os.path.join(path_backups, path)):
                continue
            if path.endswith(dirty_ext):
                # TODO: Clear the dirty file marker if it does not have a matching downloaded file
                continue
            if not path.endswith(".json"):
                path_backups_contents.append(path)

        files_to_upload = []

        for path in path_backups_contents:
            blob_path = os.path.join(path_backups, path)
            metadata_path = os.path.join(blob_path + ".json")
            if not os.path.exists(metadata_path):
                raise ConanException(f"Missing metadata file for backup source {blob_path}")
            metadata = json.loads(load(metadata_path))
            refs = metadata["references"]
            for ref, urls in refs.items():
                if not has_excluded_urls(urls) and (not only_upload
                                                    or package_list is None
                                                    or ref in all_refs):
                    files_to_upload.append(metadata_path)
                    files_to_upload.append(blob_path)
                    break
        return files_to_upload

    @staticmethod
    def update_backup_sources_json(cached_path, conanfile, urls):
        """ create or update the sha256.json file with the references and new urls used
        """
        summary_path = cached_path + ".json"
        if os.path.exists(summary_path):
            summary = json.loads(load(summary_path))
        else:
            summary = {"references": {}, "timestamp": timestamp_now()}

        try:
            summary_key = str(conanfile.ref)
        except AttributeError:
            # The recipe path would be different between machines
            # So best we can do is to set this as unknown
            summary_key = "unknown"

        if not isinstance(urls, (list, tuple)):
            urls = [urls]
        existing_urls = summary["references"].setdefault(summary_key, [])
        existing_urls.extend(url for url in urls if url not in existing_urls)
        conanfile.output.verbose(f"Updating ${summary_path} summary file")
        summary_dump = json.dumps(summary)
        conanfile.output.debug(f"New summary: ${summary_dump}")
        save(summary_path, json.dumps(summary))
