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lib/query_builder.ex
defmodule QueryBuilder do
require Ecto.Query
alias Ecto.Query
defmacro __using__(opts) do
quote do
require QueryBuilder.Schema
QueryBuilder.Schema.__using__(unquote(opts))
end
end
@doc ~S"""
Preloads the associations.
Bindings are automatically set if joins have been made, or if it is preferable to
join (i.e. one-to-one associations are preferable to include into the query result
rather than emitting separate DB queries).
Example:
```
QueryBuilder.preload(query, [role: :permissions, articles: [:stars, comments: :user]])
```
"""
def preload(query, assoc_fields) do
ensure_query_has_binding(query)
|> QueryBuilder.Query.Preload.preload(assoc_fields)
end
@doc ~S"""
An AND where query expression.
Example:
```
QueryBuilder.where(query, firstname: "John")
```
"""
def where(query, filters) do
where(query, [], filters)
end
@doc ~S"""
An AND where query expression.
Associations are passed in second argument; fields from these associations can then
be referenced by writing the field name, followed by the "@" character and the
association name, as an atom. For example: `:name@users`.
Example:
```
QueryBuilder.where(query, [role: :permissions], name@permissions: :write)
```
OR clauses may be passed through last argument `opts`. For example:
```elixir
QueryBuilder.where(query, [], [firstname: "John"], or: [firstname: "Alice", lastname: "Doe"], or: [firstname: "Bob"])
```
"""
def where(query, assoc_fields, filters, opts \\ []) do
ensure_query_has_binding(query)
|> QueryBuilder.Query.Where.where(assoc_fields, filters, opts)
end
@doc ~S"""
An order by query expression.
Example:
```
QueryBuilder.order_by(query, lastname: :asc, firstname: :asc)
```
"""
def order_by(query, value) do
order_by(query, [], value)
end
@doc ~S"""
An order by query expression.
For more about the second argument, see `where/3`.
Example:
```
QueryBuilder.order_by(query, :articles, title@articles: :asc)
```
"""
def order_by(query, assoc_fields, value) do
ensure_query_has_binding(query)
|> QueryBuilder.Query.OrderBy.order_by(assoc_fields, value)
end
@doc ~S"""
A join query expression.
Third argument `type` may be passed one of the possible values for
`Ecto.Query.join/5`'s qualifier argument.
Example:
```
QueryBuilder.join(query, :articles, :left)
```
"""
def join(query, assoc_fields, type) do
ensure_query_has_binding(query)
|> QueryBuilder.Query.Join.join(assoc_fields, type)
end
@doc ~S"""
Allows to pass a list of operations through a keyword list.
Example:
```
QueryBuilder.from_list(query, [
where: [name: "John", city: "Anytown"],
preload: [articles: :comments]
])
```
"""
def from_list(query, []), do: query
def from_list(query, [{operation, arguments} | tail]) do
arguments =
cond do
is_tuple(arguments) -> Tuple.to_list(arguments)
is_list(arguments) -> [arguments]
true -> List.wrap(arguments)
end
apply(__MODULE__, operation, [query | arguments])
|> from_list(tail)
end
defp ensure_query_has_binding(query) do
schema = QueryBuilder.Utils.root_schema(query)
unless Query.has_named_binding?(query, schema._binding()) do
schema._query()
else
query
end
end
end