__init__.py

# This file is part of beets.
# Copyright 2016, Adrian Sampson.
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.

"""A Web interface to beets."""

import base64
import json
import os

import flask
from flask import g, jsonify
from unidecode import unidecode
from werkzeug.routing import BaseConverter, PathConverter

import beets.library
from beets import ui, util
from beets.plugins import BeetsPlugin

# Utilities.


def _rep(obj, expand=False):
    """Get a flat -- i.e., JSON-ish -- representation of a beets Item or
    Album object. For Albums, `expand` dictates whether tracks are
    included.
    """
    out = dict(obj)

    if isinstance(obj, beets.library.Item):
        if app.config.get("INCLUDE_PATHS", False):
            out["path"] = util.displayable_path(out["path"])
        else:
            del out["path"]

        # Filter all bytes attributes and convert them to strings.
        for key, value in out.items():
            if isinstance(out[key], bytes):
                out[key] = base64.b64encode(value).decode("ascii")

        # Get the size (in bytes) of the backing file. This is useful
        # for the Tomahawk resolver API.
        try:
            out["size"] = os.path.getsize(util.syspath(obj.path))
        except OSError:
            out["size"] = 0

        return out

    elif isinstance(obj, beets.library.Album):
        if app.config.get("INCLUDE_PATHS", False):
            out["artpath"] = util.displayable_path(out["artpath"])
        else:
            del out["artpath"]
        if expand:
            out["items"] = [_rep(item) for item in obj.items()]
        return out


def json_generator(items, root, expand=False):
    """Generator that dumps list of beets Items or Albums as JSON

    :param root:  root key for JSON
    :param items: list of :class:`Item` or :class:`Album` to dump
    :param expand: If true every :class:`Album` contains its items in the json
                   representation
    :returns:     generator that yields strings
    """
    yield '{"%s":[' % root
    first = True
    for item in items:
        if first:
            first = False
        else:
            yield ","
        yield json.dumps(_rep(item, expand=expand))
    yield "]}"


def is_expand():
    """Returns whether the current request is for an expanded response."""

    return flask.request.args.get("expand") is not None


def is_delete():
    """Returns whether the current delete request should remove the selected
    files.
    """

    return flask.request.args.get("delete") is not None


def get_method():
    """Returns the HTTP method of the current request."""
    return flask.request.method


def resource(name, patchable=False):
    """Decorates a function to handle RESTful HTTP requests for a resource."""

    def make_responder(retriever):
        def responder(ids):
            entities = [retriever(id) for id in ids]
            entities = [entity for entity in entities if entity]

            if get_method() == "DELETE":
                if app.config.get("READONLY", True):
                    return flask.abort(405)

                for entity in entities:
                    entity.remove(delete=is_delete())

                return flask.make_response(jsonify({"deleted": True}), 200)

            elif get_method() == "PATCH" and patchable:
                if app.config.get("READONLY", True):
                    return flask.abort(405)

                for entity in entities:
                    entity.update(flask.request.get_json())
                    entity.try_sync(True, False)  # write, don't move

                if len(entities) == 1:
                    return flask.jsonify(_rep(entities[0], expand=is_expand()))
                elif entities:
                    return app.response_class(
                        json_generator(entities, root=name),
                        mimetype="application/json",
                    )

            elif get_method() == "GET":
                if len(entities) == 1:
                    return flask.jsonify(_rep(entities[0], expand=is_expand()))
                elif entities:
                    return app.response_class(
                        json_generator(entities, root=name),
                        mimetype="application/json",
                    )
                else:
                    return flask.abort(404)

            else:
                return flask.abort(405)

        responder.__name__ = f"get_{name}"

        return responder

    return make_responder


def resource_query(name, patchable=False):
    """Decorates a function to handle RESTful HTTP queries for resources."""

    def make_responder(query_func):
        def responder(queries):
            entities = query_func(queries)

            if get_method() == "DELETE":
                if app.config.get("READONLY", True):
                    return flask.abort(405)

                for entity in entities:
                    entity.remove(delete=is_delete())

                return flask.make_response(jsonify({"deleted": True}), 200)

            elif get_method() == "PATCH" and patchable:
                if app.config.get("READONLY", True):
                    return flask.abort(405)

                for entity in entities:
                    entity.update(flask.request.get_json())
                    entity.try_sync(True, False)  # write, don't move

                return app.response_class(
                    json_generator(entities, root=name),
                    mimetype="application/json",
                )

            elif get_method() == "GET":
                return app.response_class(
                    json_generator(
                        entities, root="results", expand=is_expand()
                    ),
                    mimetype="application/json",
                )

            else:
                return flask.abort(405)

        responder.__name__ = f"query_{name}"

        return responder

    return make_responder


def resource_list(name):
    """Decorates a function to handle RESTful HTTP request for a list of
    resources.
    """

    def make_responder(list_all):
        def responder():
            return app.response_class(
                json_generator(list_all(), root=name, expand=is_expand()),
                mimetype="application/json",
            )

        responder.__name__ = f"all_{name}"
        return responder

    return make_responder


def _get_unique_table_field_values(model, field, sort_field):
    """retrieve all unique values belonging to a key from a model"""
    if field not in model.all_keys() or sort_field not in model.all_keys():
        raise KeyError
    with g.lib.transaction() as tx:
        rows = tx.query(
            "SELECT DISTINCT '{}' FROM '{}' ORDER BY '{}'".format(
                field, model._table, sort_field
            )
        )
    return [row[0] for row in rows]


class IdListConverter(BaseConverter):
    """Converts comma separated lists of ids in urls to integer lists."""

    def to_python(self, value):
        ids = []
        for id in value.split(","):
            try:
                ids.append(int(id))
            except ValueError:
                pass
        return ids

    def to_url(self, value):
        return ",".join(str(v) for v in value)


class QueryConverter(PathConverter):
    """Converts slash separated lists of queries in the url to string list."""

    def to_python(self, value):
        queries = value.split("/")
        """Do not do path substitution on regex value tests"""
        return [
            query if "::" in query else query.replace("\\", os.sep)
            for query in queries
        ]

    def to_url(self, value):
        return "/".join([v.replace(os.sep, "\\") for v in value])


class EverythingConverter(PathConverter):
    part_isolating = False
    regex = ".*?"


# Flask setup.

app = flask.Flask(__name__)
app.url_map.converters["idlist"] = IdListConverter
app.url_map.converters["query"] = QueryConverter
app.url_map.converters["everything"] = EverythingConverter


@app.before_request
def before_request():
    g.lib = app.config["lib"]


# Items.


@app.route("/item/<idlist:ids>", methods=["GET", "DELETE", "PATCH"])
@resource("items", patchable=True)
def get_item(id):
    return g.lib.get_item(id)


@app.route("/item/")
@app.route("/item/query/")
@resource_list("items")
def all_items():
    return g.lib.items()


@app.route("/item/<int:item_id>/file")
def item_file(item_id):
    item = g.lib.get_item(item_id)

    # On Windows under Python 2, Flask wants a Unicode path. On Python 3, it
    # *always* wants a Unicode path.
    if os.name == "nt":
        item_path = util.syspath(item.path)
    else:
        item_path = os.fsdecode(item.path)

    base_filename = os.path.basename(item_path)
    # FIXME: Arguably, this should just use `displayable_path`: The latter
    # tries `_fsencoding()` first, but then falls back to `utf-8`, too.
    if isinstance(base_filename, bytes):
        try:
            unicode_base_filename = base_filename.decode("utf-8")
        except UnicodeError:
            unicode_base_filename = util.displayable_path(base_filename)
    else:
        unicode_base_filename = base_filename

    try:
        # Imitate http.server behaviour
        base_filename.encode("latin-1", "strict")
    except UnicodeError:
        safe_filename = unidecode(base_filename)
    else:
        safe_filename = unicode_base_filename

    response = flask.send_file(
        item_path, as_attachment=True, download_name=safe_filename
    )
    return response


@app.route("/item/query/<query:queries>", methods=["GET", "DELETE", "PATCH"])
@resource_query("items", patchable=True)
def item_query(queries):
    return g.lib.items(queries)


@app.route("/item/path/<everything:path>")
def item_at_path(path):
    query = beets.library.PathQuery("path", path.encode("utf-8"))
    item = g.lib.items(query).get()
    if item:
        return flask.jsonify(_rep(item))
    else:
        return flask.abort(404)


@app.route("/item/values/<string:key>")
def item_unique_field_values(key):
    sort_key = flask.request.args.get("sort_key", key)
    try:
        values = _get_unique_table_field_values(
            beets.library.Item, key, sort_key
        )
    except KeyError:
        return flask.abort(404)
    return flask.jsonify(values=values)


# Albums.


@app.route("/album/<idlist:ids>", methods=["GET", "DELETE"])
@resource("albums")
def get_album(id):
    return g.lib.get_album(id)


@app.route("/album/")
@app.route("/album/query/")
@resource_list("albums")
def all_albums():
    return g.lib.albums()


@app.route("/album/query/<query:queries>", methods=["GET", "DELETE"])
@resource_query("albums")
def album_query(queries):
    return g.lib.albums(queries)


@app.route("/album/<int:album_id>/art")
def album_art(album_id):
    album = g.lib.get_album(album_id)
    if album and album.artpath:
        return flask.send_file(album.artpath.decode())
    else:
        return flask.abort(404)


@app.route("/album/values/<string:key>")
def album_unique_field_values(key):
    sort_key = flask.request.args.get("sort_key", key)
    try:
        values = _get_unique_table_field_values(
            beets.library.Album, key, sort_key
        )
    except KeyError:
        return flask.abort(404)
    return flask.jsonify(values=values)


# Artists.


@app.route("/artist/")
def all_artists():
    with g.lib.transaction() as tx:
        rows = tx.query("SELECT DISTINCT albumartist FROM albums")
    all_artists = [row[0] for row in rows]
    return flask.jsonify(artist_names=all_artists)


# Library information.


@app.route("/stats")
def stats():
    with g.lib.transaction() as tx:
        item_rows = tx.query("SELECT COUNT(*) FROM items")
        album_rows = tx.query("SELECT COUNT(*) FROM albums")
    return flask.jsonify(
        {
            "items": item_rows[0][0],
            "albums": album_rows[0][0],
        }
    )


# UI.


@app.route("/")
def home():
    return flask.render_template("index.html")


# Plugin hook.


class WebPlugin(BeetsPlugin):
    def __init__(self):
        super().__init__()
        self.config.add(
            {
                "host": "127.0.0.1",
                "port": 8337,
                "cors": "",
                "cors_supports_credentials": False,
                "reverse_proxy": False,
                "include_paths": False,
                "readonly": True,
            }
        )

    def commands(self):
        cmd = ui.Subcommand("web", help="start a Web interface")
        cmd.parser.add_option(
            "-d",
            "--debug",
            action="store_true",
            default=False,
            help="debug mode",
        )

        def func(lib, opts, args):
            args = ui.decargs(args)
            if args:
                self.config["host"] = args.pop(0)
            if args:
                self.config["port"] = int(args.pop(0))

            app.config["lib"] = lib
            # Normalizes json output
            app.config["JSONIFY_PRETTYPRINT_REGULAR"] = False

            app.config["INCLUDE_PATHS"] = self.config["include_paths"]
            app.config["READONLY"] = self.config["readonly"]

            # Enable CORS if required.
            if self.config["cors"]:
                self._log.info(
                    "Enabling CORS with origin: {0}", self.config["cors"]
                )
                from flask_cors import CORS

                app.config["CORS_ALLOW_HEADERS"] = "Content-Type"
                app.config["CORS_RESOURCES"] = {
                    r"/*": {"origins": self.config["cors"].get(str)}
                }
                CORS(
                    app,
                    supports_credentials=self.config[
                        "cors_supports_credentials"
                    ].get(bool),
                )

            # Allow serving behind a reverse proxy
            if self.config["reverse_proxy"]:
                app.wsgi_app = ReverseProxied(app.wsgi_app)

            # Start the web application.
            app.run(
                host=self.config["host"].as_str(),
                port=self.config["port"].get(int),
                debug=opts.debug,
                threaded=True,
            )

        cmd.func = func
        return [cmd]


class ReverseProxied:
    """Wrap the application in this middleware and configure the
    front-end server to add these headers, to let you quietly bind
    this to a URL other than / and to an HTTP scheme that is
    different than what is used locally.

    In nginx:
    location /myprefix {
        proxy_pass http://192.168.0.1:5001;
        proxy_set_header Host $host;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Scheme $scheme;
        proxy_set_header X-Script-Name /myprefix;
        }

    From: http://flask.pocoo.org/snippets/35/

    :param app: the WSGI application
    """

    def __init__(self, app):
        self.app = app

    def __call__(self, environ, start_response):
        script_name = environ.get("HTTP_X_SCRIPT_NAME", "")
        if script_name:
            environ["SCRIPT_NAME"] = script_name
            path_info = environ["PATH_INFO"]
            if path_info.startswith(script_name):
                environ["PATH_INFO"] = path_info[len(script_name) :]

        scheme = environ.get("HTTP_X_SCHEME", "")
        if scheme:
            environ["wsgi.url_scheme"] = scheme
        return self.app(environ, start_response)