#!/usr/bin/python3
from __future__ import annotations

import os
import re
import json
import tomllib
import sys
import argparse
import asyncio
import signal
from abc import ABC, abstractmethod
from datetime import datetime
from zoneinfo import ZoneInfo
from pathlib import Path
from hashlib import sha256
from jinja2 import Template
from ttrss.client import TTRClient

import google_reader

#%% Configuration

class Config:
    def __init__(self):
        with open("config.default.toml", "rb") as f:
            default_config = tomllib.load(f)

        config_path = Path(os.environ.get("CONFIG_PATH") or "config.toml")
        if config_path.exists():
            with config_path.open("rb") as f:
                config = tomllib.load(f)
        elif "CONFIG_PATH" in os.environ:
            print(f"Configuration file {config_path} does not exist; create it or change the CONFIG_PATH environment variable to another path")
            exit(1)
        else:
            config = {}

        def get_config(category, field, can_default=True):
            env_name = f"{category.upper()}_{field.upper()}"
            c = config.get(category, {})
            if env_name in os.environ:
                return os.environ[env_name]
            elif field in c:
                return c[field]
            elif can_default:
                return default_config[category][field]
            else:
                print(f"Error while loading configuration: {category}.{field} not found in {config_path} nor in environment variable {env_name}", file=sys.stderr)
                exit(1)

        # Get config fields
        self.html_root: Path = Path(get_config("directories", "reader"))
        self.json_root: Path = Path(get_config("directories", "data"))

        self.server_api: str = str(get_config("server", "api"))
        self.server_url: str = str(get_config("server", "url", False))
        self.server_user: str = str(get_config("server", "user", False))
        self.server_password: str = str(get_config("server", "password", False))
        self.items_per_query: int = int(get_config("server", "items_per_request"))

        self.timezone: ZoneInfo = ZoneInfo(str(get_config("datetime", "timezone")))
        self.time_format: str = str(get_config("datetime", "format"))

        self.item_template: Template = Template(str(get_config("html", "template")), autoescape=True)
        self.item_filename_template: Template = Template(str(get_config("html", "filename_template")), autoescape=False)
        self.item_category_template: Template = Template(str(get_config("html", "category_template")), autoescape=False)
        self.max_filename_length: int = int(get_config("html", "max_filename_length"))
        self.filename_translation = str.maketrans(get_config("html", "filename_replacement"))

        self.daemon_sync_up_every: int = int(get_config("daemon", "sync_up_every"))
        self.daemon_sync_down_every: int = int(get_config("daemon", "sync_down_every"))

        # Computed config fields
        self.update_lock = self.json_root / "update.lock"

        # Create missing directories
        self.html_root.mkdir(exist_ok=True)
        self.json_root.mkdir(exist_ok=True)

#%% Interaction with server

type Id = int | str

class Article(ABC):
    id: Id
    title: str = ""
    published: int = 0
    updated: int = 0
    author: str = ""
    summary: str = ""
    content: str = ""
    feed_title: str = ""
    feed_url: str = ""
    feed_icon_url: str = ""
    feed_order: int = 0
    article_url: str = ""
    comments_url: str = ""
    language: str = ""
    image_url: str = ""

    def asdict(self):
        return {
            "id": self.id,
            "title": self.title,
            "published": self.published,
            "updated": self.updated,
            "author": self.author,
            "summary": self.summary,
            "content": self.content,
            "feed_title": self.feed_title,
            "feed_url": self.feed_url,
            "feed_icon_url": self.feed_icon_url,
            "feed_order": self.feed_order,
            "article_url": self.article_url,
            "comments_url": self.comments_url,
            "language": self.language,
            "image_url": self.image_url,
        }

class GReaderArticle(Article):
    def __init__(self, session: GReaderSession, item_content):
        self.id = item_content.id
        self.title = item_content.title
        self.published = item_content.published
        self.updated = item_content.updated
        self.author = item_content.author
        self.summary = item_content.summary.content
        self.content = item_content.content.content
        self.feed_title = item_content.origin.title
        self.feed_url = item_content.origin.html_url
        self.article_url = item_content.canonical[0].href

class TTRArticle(Article):
    def __init__(self, session: TRRSession, article):
        self.id = article.id
        self.title = article.title
        self.published = article.updated.timestamp()
        self.updated = article.updated.timestamp()
        self.author = article.author
        self.summary = article.excerpt
        self.content = article.content
        self.feed_title = article.feed_title
        self.feed_url = article.site_url
        self.feed_icon_url = session.feeds[article.feed_id]["icon"]
        self.feed_order = session.feeds[article.feed_id]["order"]
        self.article_url = article.link
        self.comments_url = article.comments_link
        self.language = article.lang
        self.image_url = article.flavor_image

class Category:
    id: Id
    title: str
    parents: list[Category]
    order: int = 0

    def __init__(self, id, title, parents=[], order=0):
        self.id = id
        self.title = title
        self.parents = parents
        self.order = order
    
    def asdict(self):
        return {
            "id": self.id,
            "title": self.title,
            "parents": [ dir.asdict() for dir in self.parents ],
            "order": self.order
        }

class ClientSession(ABC):
    @abstractmethod
    def mark_as_read(self, item_ids: list[Id]):
        """
        Mark all the given articles as read.
        """
        pass
    
    @abstractmethod
    def list_categories(self) -> list[Category]:
        """
        Returns a list of all the categories on the server.
        """
        pass

    @abstractmethod
    def get_unread_articles_in_category(self, category_id: Id, limit: int, continuation: int=0) -> list[Article]:
        """
        Returns a list of Articles in the given category. limit and continuation are required for pagination.
        """
        pass

label_name = re.compile("user/.*/label/(.*)")
class GReaderSession(ClientSession):
    greader: google_reader.Client
    auth_token: str
    csrf_token: str

    def __init__(self, config: Config):
        self.greader = google_reader.Client(config.server_url)
        self.auth_token = self.greader.login(config.server_user, config.server_password)
        self.csrf_token = self.greader.get_token(self.auth_token)
    
    def mark_as_read(self, item_ids: list[Id]):
        self.greader.edit_tags(self.auth_token, self.csrf_token, item_ids=item_ids, add_tags=[google_reader.STREAM_READ])
    
    def list_categories(self):
        categories = [tag for tag in self.greader.list_tags(self.auth_token) if tag.type == "folder"]
        l = []
        for category in categories:
            category_name = category.label or label_name.search(category.id).group(1)
            category_id = category.id
            l.append(Category(id=category_id, title=category_name))
        return l
    
    def get_unread_articles_in_category(self, category_id, limit=500, continuation=0):
        items_ids = self.greader.get_stream_items_ids(self.auth_token, stream_id=category_id, exclude_target="user/-/state/com.google/read", limit=limit, continuation=continuation)
        item_contents = self.greader.get_stream_items_contents(self.auth_token, self.csrf_token, item_ids=[item.id for item in items.item_refs])
        return [ GReaderArticle(self, item_content) for item_content in item_contents.items ]

class TRRSession(ClientSession):
    ttrss: TTRClient
    feeds: dict

    def __init__(self, config: Config):
        self.ttrss = TTRClient(config.server_url, config.server_user, config.server_password, auto_login=True)
        self.ttrss.login()
        self.feeds = {}
    
    def mark_as_read(self, item_ids):
        self.ttrss.mark_read(item_ids)

    def list_categories(self):
        self.feeds = {}
        def get_categories_recursive(parent_category, parent_categories=[]):
            categories = []
            index = 0
            for item in parent_category["items"]:
                # skip special categories and feeds
                if item["bare_id"] <= 0:
                    continue
                # category
                elif item.get("type") == "category":
                    category = Category(id=item["bare_id"], parents=parent_categories, title=item["name"], order=index)
                    categories.append(category)                    
                    categories += get_categories_recursive(item, parent_categories+[category])
                # feeds
                elif "type" not in item:
                    self.feeds[item["bare_id"]] = item
                    self.feeds[item["bare_id"]]["order"] = index
                index += 1
            return categories
        tree = self.ttrss.get_feed_tree()
        return get_categories_recursive(tree["categories"])
    
    def get_unread_articles_in_category(self, category_id, limit=100, continuation=0):
        headlines = self.ttrss.get_headlines(feed_id=category_id, limit=limit, skip=continuation, is_cat=True, show_excerpt=True, show_content=True, view_mode="unread", include_attachments=True, include_nested=False)
        return [ TTRArticle(self, headline) for headline in headlines ]

def make_client_session(config: Config) -> ClientSession:
    api = config.server_api
    if api == "googlereader":
        return GReaderSession(config)
    elif api == "ttrss":
        return TRRSession(config)
    else:
        print(f"Configuration error: server.api must be either ttrss or googlereader", file=sys.stderr)
        exit(1)

#%% Regular feather operations

def mark_deleted_as_read(config, client_session):
    # Mark items that are in the JSON directory but with missing HTML file as read on the server
    if config.update_lock.exists():
        print("The previous synchronization was aborted, not marking any item as read in order to avoid collateral damage")
        return

    marked_as_read = 0
    to_mark_as_read = []
    for json_path in config.json_root.glob("*.json"):
        item_json = json.load(json_path.open("r"))
        html_path = config.html_root / item_json["html_path"]
        if not html_path.exists():
            to_mark_as_read.append(item_json["id"])
            # delete JSON file
            json_path.unlink()
            marked_as_read += 1

    for i in range(0, len(to_mark_as_read), config.items_per_query):
        client_session.mark_as_read(to_mark_as_read[i:i+500])

    print(f"Marked {marked_as_read} items as read")

def escape_filename(config, filename):
    return filename.translate(config.filename_translation)

def truncate_filename(config, filename):
    max_filename_length = config.max_filename_length
    filename_utf8 = filename.encode("utf-8")
    if len(filename_utf8) <= max_filename_length:
        return filename
    else:
        suffix = Path(filename).suffix
        max_basename_length = max_filename_length - len(suffix.encode("utf-8"))
        cutoff = len(filename.encode('utf-8')[:max_basename_length].decode('utf-8', errors="ignore"))
        return filename[:cutoff] + '…' + suffix

def get_html_path(config, item_json):
    category_directory = config.html_root
    for category in item_json["category"]["parents"]:
        category_directory /= escape_filename(config, config.item_category_template.render(category))
    category_directory /= escape_filename(config, config.item_category_template.render(item_json["category"]))
    category_directory.mkdir(parents=True, exist_ok=True) # TODO move

    html_name = truncate_filename(config, escape_filename(config, config.item_filename_template.render(item_json)))

    return category_directory / html_name

def format_datetime(config, timestamp):
    return datetime.fromtimestamp(timestamp, config.timezone).strftime(config.time_format)

def set_computed_fields_json(config, item_json): # TODO: clean
    item_json["published_formatted"] = format_datetime(config, item_json["published"])
    item_json["updated_formatted"] = format_datetime(config, item_json["updated"])
    item_json["html_path"] = str(get_html_path(config, item_json).relative_to(config.html_root))

def synchronize_with_server(config, client_session):
    # Synchronize items from the server, generating and deleting JSON and HTML files accordingly
    config.update_lock.touch()
    print("Synchronizing with server...")

    new_items, updated_items = 0, 0
    grabbed_item_paths = []

    categories = client_session.list_categories()
    for category in categories:
        print(f"  Updating category {category.title}")

        remaining, continuation = True, 0
        while remaining:
            articles = client_session.get_unread_articles_in_category(category.id, limit=config.items_per_query, continuation=continuation)
            if len(articles) >= config.items_per_query:
                continuation += len(articles)
            else:
                remaining = False
            
            for item in articles:
                item_json = item.asdict()
                item_json["category"] = category.asdict()
                set_computed_fields_json(config, item_json)

                json_path = config.json_root / f"{ sha256(str(item_json["id"]).encode("utf-8")).hexdigest() }.json"
                grabbed_item_paths.append(json_path)

                write_files, updating = False, False
                if not json_path.exists():
                    write_files = True
                    new_items += 1
                else:
                    old_item_json = json.load(json_path.open("r"))
                    if item_json["updated"] > old_item_json["updated"]:
                        write_files, updating = True, True
                        updated_items += 1

                if write_files:
                    # write JSON
                    with json_path.open("w") as f:
                        json.dump(item_json, f)
                    # write HTML
                    generate_html_for_item(config, item_json, regenerate=updating)
    
    # Remove items that we didn't get from the server but are in the JSON directory
    removed_items = 0
    for item_path in config.json_root.glob("*.json"):
        if not item_path in grabbed_item_paths:
            # remove HTML
            item_json = json.load(item_path.open("r"))
            remove_html_for_item(config, item_json, ignore_deleted=True) # ignore if file was deleted by user during sync
            # remove JSON
            item_path.unlink()
            removed_items += 1
    
    print(f"Synchronization successful ({new_items} new items, {updated_items} updated, {removed_items} removed)")
    config.update_lock.unlink()

def generate_html_for_item(config, item_json, regenerate=False):
    # Write HTML file for a JSON object
    html_path = config.html_root / item_json["html_path"]
    if html_path.exists() and not regenerate:
        print(f"WARNING: a file already exist for {html_path}. Either the feed has duplicate entries, or something has gone terribly wrong.")
    else:
        with html_path.open("w") as f:
            f.write(config.item_template.render(item_json))
        # set accessed date to update time, modified to publication time
        os.utime(html_path, (max(item_json["updated"], item_json["updated"]), item_json["published"]))

def remove_html_for_item(config, item_json, ignore_deleted=False):
    # Delete a HTML file for a JSON object
    html_path = config.html_root / item_json["html_path"]
    if not ignore_deleted or html_path.exists():
        html_path.unlink()

def remove_empty_html_directories(config):
    # Remove empty directories in the HTML directory
    html_root = config.html_root
    removed_directories = set()
    for (dirpath, dirnames, filenames) in html_root.walk(top_down=False):
        if dirpath != html_root:
            is_empty = len(filenames) == 0
            if is_empty and len(dirnames) > 0: # some subdirectories may have been removed in an earlier iteration
                for subdirname in dirnames:
                    if dirpath / subdirname not in removed_directories:
                        is_empty = False
                        break
            if is_empty:
                dirpath.rmdir()
                removed_directories.add(dirpath)

def synchronize(config, client_session):
    # Do a full feather update
    mark_deleted_as_read(config, client_session)
    synchronize_with_server(config, client_session)
    remove_empty_html_directories(config)

def synchronize_local_changes(config, client_session):
    # Upload local changes (read items) to the server
    mark_deleted_as_read(config, client_session)
    remove_empty_html_directories(config)

def synchronize_remote_changes(config, client_session):
    # Download remote changes (new items, items read from another device) from the server
    synchronize_with_server(config, client_session)
    remove_empty_html_directories(config)

async def daemon_sync_up_loop(config, client_session):
    while True:
        synchronize_local_changes(config, client_session)
        await asyncio.sleep(config.daemon_sync_up_every)
async def daemon_sync_down_loop(config, client_session):
    while True:
        synchronize_remote_changes(config, client_session)
        await asyncio.sleep(config.daemon_sync_down_every)
async def daemon(config, client_session):
    print(f"Started in daemon mode; changes will be downloaded from the server every {config.daemon_sync_down_every}s and uploaded every {config.daemon_sync_up_every}s")
    async with asyncio.TaskGroup() as tg:
        tup = tg.create_task(daemon_sync_up_loop(config, client_session))
        tdown = tg.create_task(daemon_sync_down_loop(config, client_session))
        def cancel_tasks():
            tup.cancel()
            tdown.cancel()
        asyncio.get_running_loop().add_signal_handler(signal.SIGTERM, cancel_tasks)

def regenerate_files(config):
    for json_path in config.json_root.glob("*.json"):
        item_json = json.load(json_path.open("r"))
        remove_html_for_item(config, item_json, ignore_deleted=True) # path might change so we preemptively remove the old file
        set_computed_fields_json(config, item_json) # recompute formatted datetime & path from the current configuration
        # rewrite JSON
        with json_path.open("w") as f:
            json.dump(item_json, f)
        # rewrite HTML
        generate_html_for_item(config, item_json, regenerate=True)

def clear_data(config):
    for json_path in config.json_root.glob("*.json"):
        item_json = json.load(json_path.open("r"))
        remove_html_for_item(config, item_json, ignore_deleted=True)
        json_path.unlink()
    remove_empty_html_directories(config)

#%% Run feather

def main():
    parser = argparse.ArgumentParser(
        prog="feather",
        description="file-based RSS reader client"
    )
    parser.add_argument(
        "action", choices=("sync", "sync-up", "sync-down", "daemon", "regenerate", "clear-data"),
        help="sync: perform a full synchronization with the server; sync-up: only synchronize local changes to the server (e.g. items read locally); sync-down: only synchronize remote change from the server (e.g. new items or items read from another device); daemon: start in daemon mode (will keep performing synchronizations periodically until process is stopped); regenerate: regenerate all HTML files from the local data; clear-data: remove all local data"
    )
    args = parser.parse_args()

    config = Config()
    if args.action == "sync":
        client_session = make_client_session(config)
        synchronize(config, client_session)
    elif args.action == "sync-up":
        client_session = make_client_session(config)
        synchronize_local_changes(config, client_session)
    elif args.action == "sync-down":
        client_session = make_client_session(config)
        synchronize_remote_changes(config, client_session)
    elif args.action == "daemon":
        client_session = make_client_session(config)
        try:
            asyncio.run(daemon(config, client_session))
        except KeyboardInterrupt:
            pass
    elif args.action == "regenerate":
        regenerate_files(config)
    elif args.action == "clear-data":
        clear_data(config)

if __name__ == "__main__":
    main()