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Sami Samhuri
97105c1501
Add Pressa::OpenGraph, a best-effort scraper that pulls og:image (falling back to twitter:image) from a linked page's HTML. bake new_link and bake preview_link now use it to prefill the Image front-matter field for link posts, unless the payload already supplies one. Network failures and missing tags just resolve to nil so creating a post never blocks on a slow or broken link; the fetch happens once at draft-creation time, not on every build.
67 lines
2 KiB
Ruby
67 lines
2 KiB
Ruby
require "net/http"
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require "uri"
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module Pressa
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# Best-effort scraper for OpenGraph metadata on a linked page, used to fill
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# in an Image for link posts. Never raises: network failures, timeouts, and
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# missing tags all just resolve to a nil image so post creation never blocks
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# on a flaky or slow third-party site.
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class OpenGraph
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Result = Data.define(:image)
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USER_AGENT = "samhuri.net-link-preview/1.0".freeze
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MAX_REDIRECTS = 5
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def self.fetch(url, http_get: method(:http_get))
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html = http_get.call(url)
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return nil if html.nil?
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extract(html, base_url: url)
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rescue
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nil
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end
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def self.extract(html, base_url:)
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image = meta_content(html, "og:image") || meta_content(html, "twitter:image")
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return nil if image.nil?
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Result.new(image: resolve(image, base_url:))
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end
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def self.meta_content(html, property)
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pattern = /<meta\s+[^>]*(?:property|name)\s*=\s*["']#{Regexp.escape(property)}["'][^>]*>/i
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tag = html[pattern]
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return nil unless tag
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content = tag[/content\s*=\s*["']([^"']*)["']/i, 1]
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content&.strip&.then { |value| value.empty? ? nil : value }
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end
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def self.resolve(image, base_url:)
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URI.join(base_url, image).to_s
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rescue URI::InvalidURIError, URI::InvalidComponentError
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image
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end
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def self.http_get(url, redirects_left: MAX_REDIRECTS)
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return nil if redirects_left < 0
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uri = URI.parse(url)
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return nil unless uri.is_a?(URI::HTTP)
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Net::HTTP.start(uri.host, uri.port, use_ssl: uri.scheme == "https", open_timeout: 5, read_timeout: 5) do |http|
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response = http.get(uri.request_uri, "User-Agent" => USER_AGENT)
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case response
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when Net::HTTPSuccess
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response.body
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when Net::HTTPRedirection
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location = response["location"]
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return nil unless location
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http_get(URI.join(url, location).to_s, redirects_left: redirects_left - 1)
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end
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end
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end
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end
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end
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