defmodule HtmlQuery do
# @related [test](/test/html_query_test.exs)
@moduledoc """
A concise HTML query API. HTML parsing is handled by [Floki](https://hex.pm/packages/floki).
## Data types
All functions can accept HTML in the form of a string, a Floki HTML tree, a Floki HTML node, or anything that
implements the `String.Chars` protocol. See `t:HtmlQuery.html/0`.
Some functions take a CSS selector, which can be a string, a keyword list, or a list.
See `t:HtmlQuery.Css.selector/0`.
## Query functions
| `all/2` | return all elements matching the selector |
| `find/2` | return the first element that matches the selector |
| `find!/2` | return the only element that matches the selector, or raise |
## Extraction functions
| `attr/2` | returns the attribute value as a string |
| `form_fields/1` | returns the names and values of form fields as a map |
| `meta_tags/1` | returns the names and values of metadata fields |
| `table/2` | returns the cells of a table as a list of lists |
| `text/1` | returns the text contents as a single string |
## Parsing functions
| `parse/1` | parses an HTML fragment into a [Floki HTML tree] |
| `parse_doc/1` | parses an HTML doc into a [Floki HTML tree] |
## Utility functions
| `inspect_html/2` | prints prettified HTML with a label |
| `normalize/1` | parses and re-stringifies HTML |
| `pretty/1` | prettifies HTML |
| `reject/2` | removes nodes that match the selector |
## Alias
If you use HtmlQuery a lot, you may want to alias it to the recommended shortcut "Hq":
```elixir
alias HtmlQuery, as: Hq
```
## Examples
Get the value of a selected option:
```elixir
iex> html = ~s|<select> <option value="a" selected>apples</option> <option value="b">bananas</option> </select>|
iex> HtmlQuery.find(html, "select option[selected]") |> HtmlQuery.attr("value")
"a"
```
Get the text of a selected option, raising if there are more than one:
```elixir
iex> html = ~s|<select> <option value="a" selected>apples</option> <option value="b">bananas</option> </select>|
iex> HtmlQuery.find!(html, "select option[selected]") |> HtmlQuery.text()
"apples"
```
Get the text of all the options:
```elixir
iex> html = ~s|<select> <option value="a" selected>apples</option> <option value="b">bananas</option> </select>|
iex> HtmlQuery.all(html, "select option") |> Enum.map(&HtmlQuery.text/1)
["apples", "bananas"]
```
Use a keyword list as the selector (see `HtmlQuery.Css` for details on selectors):
```elixir
iex> html = ~s|<div> <a href="/logout" test-role="logout-link">logout</a> </div>|
iex> HtmlQuery.find!(html, test_role: "logout-link") |> HtmlQuery.attr("href")
"/logout"
```
"""
alias HtmlQuery.QueryError
@module_name __MODULE__ |> Module.split() |> Enum.join(".")
@typedoc "A string or atom representing an attribute name. If an atom, underscores are converted to dashes."
@type attr() :: binary() | atom()
@typedoc """
A string, a struct that implements the `String.Chars` protocol,
a [Floki HTML tree], or a [Floki HTML node].
[Floki HTML tree]: https://hexdocs.pm/floki/Floki.html#t:html_tree/0
[Floki HTML node]: https://hexdocs.pm/floki/Floki.html#t:html_node/0
"""
@type html() :: binary() | String.Chars.t() | Floki.html_tree() | Floki.html_node()
# # # Main Query Functions
@doc """
Finds all elements in `html` that match `selector`, returning a Floki HTML tree.
```elixir
iex> html = ~s|<select> <option value="a" selected>apples</option> <option value="b">bananas</option> </select>|
iex> HtmlQuery.all(html, "option")
[
{"option", [{"value", "a"}, {"selected", "selected"}], ["apples"]},
{"option", [{"value", "b"}], ["bananas"]}
]
```
"""
@spec all(html(), HtmlQuery.Css.selector()) :: Floki.html_tree()
def all(html, selector),
do: html |> parse() |> Floki.find(HtmlQuery.Css.selector(selector))
@doc """
Finds the first element in `html` that matches `selector`, returning a Floki HTML node.
```elixir
iex> html = ~s|<select> <option value="a" selected>apples</option> <option value="b">bananas</option> </select>|
iex> HtmlQuery.find(html, "select option[selected]")
{"option", [{"value", "a"}, {"selected", "selected"}], ["apples"]}
```
"""
@spec find(html(), HtmlQuery.Css.selector()) :: Floki.html_node() | nil
def find(html, selector),
do: all(html, selector) |> List.first()
@doc """
Like `find/2` but raises unless exactly one element is found.
"""
@spec find!(html(), HtmlQuery.Css.selector()) :: Floki.html_node()
def find!(html, selector),
do: all(html, selector) |> first!("Selector: #{HtmlQuery.Css.selector(selector)}")
# # # Extraction Functions
@doc """
Returns the value of `attr` from the outermost element of `html`.
If `attr` is an atom, any underscores are converted to dashes.
```elixir
iex> html = ~s|<div> <a href="/logout" test-role="logout-link">logout</a> </div>|
iex> HtmlQuery.find!(html, test_role: "logout-link") |> HtmlQuery.attr("href")
"/logout"
```
"""
@spec attr(html(), attr()) :: binary() | nil
def attr(nil, _attr),
do: nil
def attr(html, attr) do
html
|> parse()
|> first!("Consider using Enum.map(html, &#{@module_name}.attr(&1, #{inspect(attr)}))")
|> Floki.attribute(attr |> to_string() |> Moar.String.dasherize())
|> List.first()
end
@doc """
Returns a map containing the form fields of form `selector` in `html`. Because it returns a map, any information
about the order of form fields is lost.
```elixir
iex> html = ~s|<form> <input type="text" name="color" value="green"> <textarea name="desc">A tree</textarea> </form>|
iex> html |> HtmlQuery.find("form") |> HtmlQuery.form_fields()
%{color: "green", desc: "A tree"}
```
Field names are converted to snake case atoms:
```elixir
iex> html = ~s|<form> <input type="text" name="favorite-color" value="green"> </form>|
iex> html |> HtmlQuery.find("form") |> HtmlQuery.form_fields()
%{favorite_color: "green"}
```
If form field names are in `foo[bar]` format, then `foo` becomes a key to a nested map containing `bar`:
```elixir
iex> html = ~s|<form> <input type="text" name="profile[name]" value="fido"> <input type="text" name="profile[age]" value="10"> </form>|
iex> html |> HtmlQuery.find("form") |> HtmlQuery.form_fields()
%{profile: %{name: "fido", age: "10"}}
```
If a text field has no value attribute, it will not be returned at all:
```elixir
iex> html = ~s|<form> <input type="text" name="no-value"> </form>|
iex> html |> HtmlQuery.find("form") |> HtmlQuery.form_fields()
%{}
iex> html = ~s|<form> <input type="text" name="empty-value" value=""> </form>|
iex> html |> HtmlQuery.find("form") |> HtmlQuery.form_fields()
%{empty_value: ""}
iex> html = ~s|<form> <input type="text" name="non-empty-value" value="something"> </form>|
iex> html |> HtmlQuery.find("form") |> HtmlQuery.form_fields()
%{non_empty_value: "something"}
```
The checked value of a radio button set is returned, or `nil` is returned if no value is checked:
```elixir
iex> html = ~s|<form> <input type="radio" name="x" value="1"> <input type="radio" name="x" value="2" checked> </form>|
iex> html |> HtmlQuery.find("form") |> HtmlQuery.form_fields()
%{x: "2"}
iex> html = ~s|<form> <input type="radio" name="x" value="1"> <input type="radio" name="x" value="2"> </form>|
iex> html |> HtmlQuery.find("form") |> HtmlQuery.form_fields()
%{x: nil}
```
All checked values of checkboxes are returned as a list, or `[]` is returned if no values are checked:
```elixir
iex> html = ~s|<form> <input type="checkbox" name="x" value="1" checked> <input type="checkbox" name="x" value="2" checked> </form>|
iex> html |> HtmlQuery.find("form") |> HtmlQuery.form_fields()
%{x: ["1", "2"]}
iex> html = ~s|<form> <input type="checkbox" name="x" value="1"> <input type="checkbox" name="x" value="2"> </form>|
iex> html |> HtmlQuery.find("form") |> HtmlQuery.form_fields()
%{x: []}
```
"""
@spec form_fields(html()) :: %{atom() => binary() | map()}
def form_fields(html),
do: HtmlQuery.Form.fields(html)
@doc """
Extracts all the meta tags from `html`, returning a list of maps.
```elixir
iex> html = ~s|<head> <meta charset="utf-8"/> <meta http-equiv="X-UA-Compatible" content="IE=edge"/> </head>|
iex> HtmlQuery.meta_tags(html)
[%{"charset" => "utf-8"}, %{"content" => "IE=edge", "http-equiv" => "X-UA-Compatible"}]
```
"""
@spec meta_tags(html()) :: [%{binary() => binary()}]
def meta_tags(html),
do: html |> parse() |> extract_meta_tags()
@doc """
Returns the contents of the table as a list of lists.
Options:
* `as` - if `:lists` (the default), returns the table as a list of lists; if `:maps`, returns the table as a list of
maps.
* `columns` - a list of the indices of the columns to return; a list of column headers (as strings) to return,
assuming that the first row of the table is the columns names; or `:all` to return all columns (which is the same
as not specifying this option all all).
* `headers` - if `true` (the default), returns the list of headers along with the rows. Ignored if `as` option is
`:map`.
```elixir
iex> html = "<table> <tr><th>A</th><th>B</th><th>C</th></tr> <tr><td>1</td><td>2</td><td>3</td></tr> </table>"
iex> HtmlQuery.table(html)
[
["A", "B", "C"],
["1", "2", "3"]
]
iex> HtmlQuery.table(html, as: :maps)
[
%{"A" => "1", "B" => "2", "C" => "3"}
]
iex> HtmlQuery.table(html, columns: [0, 2])
[
["A", "C"],
["1", "3"]
]
iex> HtmlQuery.table(html, columns: [2, 0])
[
["C", "A"],
["3", "1"]
]
iex> HtmlQuery.table(html, columns: ["C", "A"])
[
["C", "A"],
["3", "1"]
]
iex> HtmlQuery.table(html, columns: ["C", "A"], headers: false)
[
["3", "1"]
]
```
"""
@spec table(html(), keyword()) :: [[]]
def table(html, opts \\ []) do
rows = [header_row | non_header_rows] = html |> parse() |> all("tr")
columns =
case Keyword.get(opts, :columns) do
nil -> :all
:all -> :all
[first | _] = indices when is_integer(first) -> indices
[first | _] = names when is_binary(first) -> header_row |> table_row_values() |> Moar.Enum.find_indices!(names)
end
case Keyword.get(opts, :as, :lists) do
:lists ->
rows =
case Keyword.get(opts, :headers, true) do
false -> non_header_rows
true -> rows
other -> raise "Expected `:headers` option to be `true` or `false`, got: #{other}"
end
Enum.map(rows, &table_row_values(&1, columns))
:maps ->
rows
|> Enum.map(&table_row_values(&1, columns))
|> Moar.Enum.lists_to_maps(:first_list)
other ->
raise "Expected `:as` option to be `:lists` or `:maps`, got: #{other}"
end
end
@doc """
Returns the text value of `html`.
```elixir
iex> html = ~s|<select> <option value="a" selected>apples</option> <option value="b">bananas</option> </select>|
iex> HtmlQuery.find!(html, "select option[selected]") |> HtmlQuery.text()
"apples"
```
"""
@spec text(html()) :: binary()
def text(html) do
html
|> parse()
|> first!("Consider using Enum.map(html, &#{@module_name}.text/1)")
|> Floki.text(sep: " ")
|> String.trim()
end
# # # Parsing Functions
@doc """
Parses an HTML fragment using `Floki.parse_fragment!/1`, returning a Floki HTML tree.
"""
@spec parse(html()) :: Floki.html_tree()
def parse(html) when is_binary(html), do: html |> Floki.parse_fragment!()
def parse(html) when is_list(html), do: html
def parse({element, attrs, contents}), do: [{element, attrs, contents}]
def parse(%_{} = html), do: html |> Moar.Protocol.implements!(String.Chars) |> to_string() |> parse()
@doc """
Parses an HTML document using `Floki.parse_document!/1`, returning a Floki HTML tree.
"""
@spec parse_doc(html()) :: Floki.html_tree()
def parse_doc(html) when is_binary(html), do: html |> Floki.parse_document!()
def parse_doc(html) when is_list(html), do: html
def parse_doc(%_{} = html), do: html |> Moar.Protocol.implements!(String.Chars) |> to_string() |> parse_doc()
# # # Utility Functions
@doc """
Prints prettified `html` with a label, and then returns the original html.
"""
@spec inspect_html(html(), binary()) :: html()
def inspect_html(html, label \\ "INSPECTED HTML") do
"""
=== #{label}:
#{pretty(html)}
"""
|> IO.puts()
html
end
@doc """
Parses and then re-stringifies `html`, increasing the liklihood that two equivalent HTML strings can
be considered equal.
```elixir
iex> a = ~s|<p id="color">green</p>|
iex> b = ~s|<p id = "color" >green</p>|
iex> a == b
false
iex> HtmlQuery.normalize(a) == HtmlQuery.normalize(b)
true
```
"""
@spec normalize(html()) :: binary()
def normalize(html),
do: html |> parse() |> Floki.raw_html()
@doc """
Returns `html` as a prettified string (delgates to `Floki.raw_html/2` with the `pretty: true` option).
"""
@spec pretty(html()) :: binary()
def pretty(html),
do: html |> parse() |> Floki.raw_html(encode: false, pretty: true)
@doc """
Returns `html` after removing all nodes that don't match `selector` (delegates to `Floki.filter_out/2`).
```elixir
iex> html = ~s|<div> <span id="name">Alice</span> <span id="password">topaz</span> </div>|
iex> HtmlQuery.reject(html, id: "password") |> HtmlQuery.normalize()
~s|<div><span id="name">Alice</span></div>|
```
"""
@spec reject(html(), HtmlQuery.Css.selector()) :: html()
def reject(html, selector),
do: html |> parse() |> Floki.filter_out(HtmlQuery.Css.selector(selector))
# # # Private Functions
@spec extract_meta_tags(html()) :: [map()]
defp extract_meta_tags(html),
do: all(html, "meta") |> Enum.map(fn {"meta", attrs, _} -> Map.new(attrs) end)
@spec first!(html(), binary()) :: html()
defp first!([], hint) do
raise(QueryError, """
Expected a single HTML node but found none
#{hint}
""")
end
defp first!([node], _hint), do: node
defp first!(html, hint) do
raise QueryError, """
Expected a single HTML node but got:
#{pretty(html)}
#{hint}
"""
end
@spec table_row_values(html(), :all | [integer()]) :: [binary()]
defp table_row_values(row, columns \\ :all),
do: row |> all("td,th") |> Moar.Enum.take_at(columns) |> Enum.map(&text/1)
end
