defmodule Link do
@moduledoc """
`Link` is a little link parsing, compacting and shortening library.
"""
@doc """
`compact/1` reduces a url to its most compact form.
This is highly specific to our use case.
## Examples
iex> Link.compact("https://github.com/dwyl/mvp/issues/141")
"dwyl/mvp#141"
# Can't understand the URL, just return it sans protocol:
iex> Link.compact("https://git.io/top")
"git.io/top"
iex> Link.compact("https://mvp.fly.dev/")
"mvp.fly.dev"
iex> Link.compact("https://github.com/dwyl/link")
"dwyl/link"
"""
def compact(url) do
# This uses cond instead of "if" because it will expand soon!
cond do
String.contains?(url, "github") ->
compact_github_url(url)
true ->
url
|> strip_protocol()
|> strip_trailing_slash()
end
end
@doc """
`compact_github_url/1` does exactly as its' name implies:
compact a GitHub URL down to it's simplest version
so that we aren't wasting characters on a mobile screen.
## Examples
iex> Link.compact_github_url("https://github.com/dwyl/mvp/issues/141")
"dwyl/mvp#141"
iex> Link.compact_github_url("https://github.com/dwyl/app/issues/275#issuecomment-1646862277")
"dwyl/app#275"
iex> Link.compact_github_url("https://github.com/dwyl/link")
"dwyl/link"
iex> Link.compact_github_url("https://github.com/dwyl/link#123")
"dwyl/link"
iex> Link.compact_github_url("https://github.com/dwyl/link/pull/5")
"dwyl/link/PR#5"
"""
def compact_github_url(url) do
# Remove any hash (#) URL params, remove "https://" and "github.com/"
clean =
String.split(url, "#")
|> List.first()
|> strip_protocol()
|> String.replace("github.com/", "")
cond do
# "dwyl/mvp/issues/141"
String.contains?(url, "/issues/") ->
parts = String.split(clean, "/")
org = Enum.at(parts, 0)
project = Enum.at(parts, 1)
issue_number = Enum.at(parts, 3)
# Assemble into the compact form:
"#{org}/#{project}##{issue_number}"
# dwyl/link/pull/5
String.contains?(url, "/pull/") ->
parts = String.split(clean, "/")
org = Enum.at(parts, 0)
project = Enum.at(parts, 1)
pr_number = Enum.at(parts, 3)
# Assemble into the compact form:
"#{org}/#{project}/PR##{pr_number}"
true ->
# Orgs, People or Repos just return path e.g: "dwyl/app" or "iteles"
clean
end
end
@doc """
`strip_protocol/1` strips the protocol e.g: "https://" from a URL.
## Examples
iex> Link.strip_protocol("https://dwyl.com")
"dwyl.com"
"""
def strip_protocol(url) do
String.replace(url, ~r"(http(s)?):\/\/", "")
end
@doc """
`strip_trailing_slash/1` strips trailing forward slash from URL.
## Examples
iex> Link.strip_trailing_slash("dwyl.com/")
"dwyl.com"
"""
def strip_trailing_slash(url) do
if String.ends_with?(url, "/") && url != "/" do
String.slice(url, 0..-2)
else
url
end
end
@doc """
`regex/0` returns the Regular Expression needed to match URLs.
According to `RFC 3986`: https://www.rfc-editor.org/rfc/rfc3986
Based on reading https://mathiasbynens.be/demo/url-regex
After much searching on Google, GitHub and StackOverflow,
this is what we came up with.
#HELPWANTED: if you find a *better* (faster, more comppliant) RegEx
that passes all our tests, please share! github.com/dwyl/link/issues/new
Explanation:
((http(s)?):\/\/ # Optional scheme (http or https)
(www\.)? # Optional "www"
a-zA-Z0-9@:%._\+~#=]{2,256} # Domain (IPv4, IPv6 or hostname)
:% # Optional port number
[a-z]{2,6}\b # Domain extension e.g: ".com"
(?:\?[^\n\r]*)? # Optional query string ?q=
(?:#[^\n\r]*)? # Optional fragment e.g: #comment
## Examples
iex> Regex.run(Link.regex(), "dwyl.com") |> List.flatten |> Enum.filter(& &1 != "") |> List.first
"dwyl.com"
"""
def regex do
~r|[(http(s)?):\/\/(www\.)?a-zA-Z0-9@:%._\+~#=]{2,256}\.[a-z]{2,14}\b([-a-zA-Z0-9@:%_\+.~#?&//=]*)|
end
@doc """
`valid?/1` confirms if a URL is valid
using the `RFC 3986` compliant `regex/0` above.
## Examples
iex> Link.valid?("example.c")
false
iex> Link.valid?("https://www.example.com")
true
"""
def valid?(url) do
Regex.match?(regex(), url)
end
@doc """
`find/1` finds all instances of a URL in a block of text.
## Examples
iex> Link.find("Text with links http://goo.gl/3co4ae and https://git.io/top & www.dwyl.com etc.")
["http://goo.gl/3co4ae", "https://git.io/top", "www.dwyl.com"]
# Find a link without any other text or whitespace #8
iex> Link.find("https://github.com/dwyl/link/pull/5#pullrequestreview-1558913764")
["https://github.com/dwyl/link/pull/5#pullrequestreview-1558913764"]
"""
def find(text) do
Regex.scan(regex(), text)
|> Enum.map(&hd/1)
# Reject URL with 3 dots i.e. JS spread operator `...numbers`
# Ref: github.com/dwyl/link/issues/6
|> Enum.reject(&String.contains?(&1, "..."))
# Avoid replacing links with lower specificity
|> Enum.sort_by(&String.length/1, :desc)
end
# Add then remove the spacer to the end of any text #8
@spacer " |コナミコマンド"
@doc """
`find_replace_compact/1` finds all instances of a URL in a block of text
and replaces them with the `compact/1` version.
Only compact the links that aren't surrounded by brackets "()"
i.e: "This is our MVP: https://mvp.fly.dev/ please try it!"
Becomes "This is our MVP: [mvp.fly.dev](https://mvp.fly.dev/) please try it!"
But if the text *already* has a Markdown link or an image, don't compact the URL!
e.g: "Please try our App: [app.dwyl.com](https://app.dwyl.com/) feedback welcome!"
No change required because it's *already* hyperlinked.
## Examples
iex> md = "# Hello World! https://github.com/dwyl/mvp/issues/141#issuecomment-1657954420 and https://mvp.fly.dev/ "
iex> Link.find_replace_compact(md)
"# Hello World! [dwyl/mvp#141](https://github.com/dwyl/mvp/issues/141#issuecomment-1657954420) and [mvp.fly.dev](https://mvp.fly.dev/) "
# Does not attempt to compact an existing markdown [link](https://github.com/dwyl/link) or 
iex> md = "existing markdown [link](https://github.com/dwyl/link) or "
iex> Link.find_replace_compact(md)
"existing markdown [link](https://github.com/dwyl/link) or "
iex> Link.find_replace_compact("https://github.com/dwyl/link/pull/5#pullrequestreview-1558913764")
iex> "[dwyl/link/PR#5](https://github.com/dwyl/link/pull/5#pullrequestreview-1558913764)"
"""
def find_replace_compact(text) do
# Spacer added to text as workaround for #8
text = text <> @spacer
find(text)
|> Enum.reduce(text, fn link, str ->
# Find the Link's position in the original text:
# stackoverflow.com/questions/35551072/find-index-of-a-substring
{pos, len} = :binary.match(text, link)
# Get character immediately after the link in the text:
char = String.at(text, pos + len)
# IO.inspect("#{text} -> #{link} -> #{char}")
# Only replace links that have whitespace or forward slash at the end:
if char == "\n" || char == "\r" || char == "\s" || char == "/" do
# Create markdown link preserving the whitespace char:
md_link = "[#{compact(link)}](#{link})#{char}"
# Replace instance of link with char in str (text)
String.replace(str, link <> char, md_link)
else
str
end
|> String.split(@spacer) |> List.first()
end)
# Strip @spacer from text: link/issues/13
|> String.replace(@spacer, "")
end
@doc """
`add_target_blank/1` Adds the target="_blank" attribute to links
so that links open in a new Tab/Window.
## Examples
iex> Link.add_target_blank(~s(My <a href="https://link.com">Link</a>))
~s(My <a target="_blank" href="https://link.com">Link</a>)
"""
def add_target_blank(text) do
String.replace(text, "<a href=", "<a target=\"_blank\" href=")
end
end
