[nit.git] / contrib / rss_downloader / src / rss_downloader.nit

# This file is part of NIT ( http://www.nitlanguage.org ).
#
# Copyright 2014 Alexis Laferrière <alexis.laf@xymus.net>
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# Downloads files from RSS feeds
module rss_downloader

import curl

redef class Sys
        # Lazy man's verbose option
        var verbose: Bool = args.has("-v") or args.has("--verbose") is lazy
end

# Program configuration
class Config

        # Folders used to infer regex (may be empty)
        var regex_source_folders: Array[Path]

        # Custom patterns (may be empty)
        var custom_patterns: Array[Pattern]

        # Download destination
        var download_destination_folder: Path

        # RSS feeds (needs at least one)
        var rss_source_urls: Array[Text]

        # Path to the log file
        var log_path: Path

        # Unique path of files names to prevent double download (may be empty)
        var unique_pattern: Array[Pattern]

        # Exception where we ignore uniqueness and can be downloaded again (may be empty)
        var unique_exceptions: Array[Pattern]
end

# An element from an RSS feed
class Element
        # Tile
        var title: String

        # Link to the file to download
        var link: String

        redef fun to_s do return "{title} @ {link}"

        # Download this element to `path`
        fun download_to(path: Text)
        do
                var request = new CurlHTTPRequest(link)
                var response = request.download_to_file(path.to_s)

                if response isa CurlResponseFailed then
                        sys.stderr.write "Failed downloading URL '{link}' with: {response.error_msg} ({response.error_code})\n"
                end
        end

        # Get an unique identifier for this element, uses `Config::unique_pattern`
        fun unique_id(config: Config): String
        do
                for re in config.unique_pattern do
                        var match = title.search(re)
                        if match != null then
                                return title.substring(0, match.after).to_lower
                        end
                end

                return title
        end

        # Is this element except from uniqueness?
        fun is_unique_exception(config: Config): Bool
        do
                for re in config.unique_exceptions do
                        if title.has(re) then
                                return true
                        end
                end
                return false
        end
end

# Main program structure
class Downloader
        # Configuration
        var config: Config

        # Local history (read from, them written to file)
        var history = new HashSet[Text]

        # Execute tool
        fun run
        do
                # Read old log from file
                if config.log_path.exists then
                        var stream = config.log_path.open_ro
                        history.add_all stream.read_all.split("\n")
                        stream.close
                end

                # Get the pattern to search for
                var patterns = self.patterns

                # Get all the elements from the RSS feeds
                var elements = new HashSet[Element]
                for rss_url in config.rss_source_urls do
                        var rss = rss_url.fetch_rss_content
                        elements.add_all rss.to_rss_elements
                end

                # Select the elements matching our pattern
                var matches = new HashSet[Element]
                for pattern in patterns do for element in elements do
                        if element.title.has(pattern) then
                                matches.add element
                        end
                end

                if sys.verbose then
                        print "\n# {matches.length} matching elements:"
                        print matches.join("\n")
                        print "\n# Downloading..."
                end

                for element in matches do
                        var local_path = config.download_destination_folder.to_s / element.title
                        var unique_id = element.unique_id(config)

                        if local_path.to_path.exists then
                                # Do not redownload a file (we assume that the file name is unique by itself)
                                if sys.verbose then print "File exists, skipping {element}"
                                continue
                        else if history.has(unique_id) then
                                # Do not download a file that is not unique according to `unique_id`
                                if not element.is_unique_exception(config) then
                                        # We make some exceptions
                                        if sys.verbose then print "File in log, skipping {element}"
                                        continue
                                end
                        end

                        # Download element
                        if sys.verbose then print "Fetching {element} as {local_path}"
                        element.download_to(local_path)

                        # Add `unique_id` to log
                        history.add unique_id
                end

                # Save new log to file
                var stream = config.log_path.open_wo
                for line in history do
                        stream.write line
                        stream.write "\n"
                end
                stream.close
        end

        # Gather all patterns from `Config::custom_patterns` and `Config::source_folder_path`
        fun patterns: Array[Pattern]
        do
                var patterns = new Array[Pattern]

                # Begin with custom pattern
                for pattern_source in config.custom_patterns do
                        patterns.add pattern_source
                end

                # Get regex source from folder names
                var folder_names = new HashSet[Text]
                for source_folder_path in config.regex_source_folders do
                        var source_folder = source_folder_path

                        if not source_folder.exists then
                                sys.stderr.write "Regex source folder '{source_folder_path}' does not exists.\n"
                                continue
                        end

                        for dir in source_folder.files do if dir.stat.is_dir then
                                folder_names.add dir.to_s
                        end
                end

                # Compile our infered patterns
                for folder_name in folder_names do
                        # Transform from "Some folder name" to "^Some.folder.name"
                        var regex_source = folder_name.
                                replace(' ', ".").replace('[', "\\[").replace('(', "\\(").
                                replace('+', "\\+").replace('*', "\\*")
                        regex_source = "^" + regex_source

                        var regex = regex_source.to_re
                        regex.ignore_case = true

                        patterns.add regex
                end

                if patterns.is_empty then
                        sys.stderr.write "Do not have any pattern to work with.\n"
                        exit 1
                end

                if sys.verbose then
                        print "# Generated {patterns.length} patterns"
                        print patterns.join("\n")
                end

                return patterns
        end
end

redef class Text
        # Get the content of the RSS feed at `self`
        fun fetch_rss_content: Text
        do
                if sys.verbose then print "\n# Downloading RSS file from '{self}'"

                var request = new CurlHTTPRequest(to_s)
                var response = request.execute

                if response isa CurlResponseSuccess then
                        var body = response.body_str
                        if sys.verbose then print "Download successful"
                        return body
                else if response isa CurlResponseFailed then
                        sys.stderr.write "Failed downloading URL '{self}' with: {response.error_msg} ({response.error_code})\n"
                        exit 1
                end

                abort
        end

        # Get this RSS feed content as an `Array[Element]`
        fun to_rss_elements: Array[Element]
        do
                var title_re = "<title><![^/]*</title>".to_re
                var link_re = "<link>[^<]*download[^<]*</link>".to_re

                var title_prefix_len = "<title><![CDATA[".length
                var title_suffix_len = "]]</title>".length+1

                var titles = search_all(title_re)
                var links = search_all(link_re)

                if sys.verbose then print "\n# Found {titles.length} titles and {links.length} links"
                assert titles.length == links.length

                var elements = new Array[Element]
                for i in titles.length.times do
                        var title = titles[i].to_s.substring(title_prefix_len, titles[i].length - title_prefix_len - title_suffix_len)
                        var link = links[i].to_s.substring(6, links[i].length - 6 - 7)
                        elements.add new Element(title, link)
                end

                if sys.verbose then
                        print "# Found elements:"
                        print elements.join("\n")
                end

                return elements
        end
end

# Implement this method in your module to configure this tool
fun tool_config: nullable Config do return null

var c = tool_config
if c == null then
        print "This tool is not configured, take a look at the example `sample_config.nit`"
        exit 1
        abort # For the flow only
end

var tool = new Downloader(c)
tool.run