extructure

defmodule ExtructureTest do
  use ExUnit.Case
  doctest Extructure

  import Extructure

  test "default map" do
    %{ a, b: %{  c}} <~ %{ a: 1, b: %{ c: 3}}
    assert a == 1
    assert c == 3
  end

  test "default list" do
    [ a, b: [ c]] <~ [ a: 1, b: [ c: 3]]
    assert a == 1
    assert c == 3
  end

  test "default (loose) tuple" do
    { a, c} <~ { { :a, 1}, { :c, 3}}
    assert a == 1
    assert c == 3
  end

  test "default mixed structures" do
    %{ a: { b, c}, d: [ e, f]} <~ %{ a: { { :b, 1}, { :c, 2}}, d: [ e: 3, f: 4]}
    assert b == 1
    assert c == 2
    assert e == 3
    assert f == 4
  end

  test "failed variable pattern match" do
    assert_raise MatchError, fn ->
      %{ a, b: %{ d}} <~ %{ a: 1, b: %{ c: 3}}
      assert a == 1
      assert d == nil
    end
  end

  test "optional variable in a map" do
    %{ _a, b: %{ c}} <~ %{ b: %{ c: 3}}
    assert a == nil
    assert c == 3
  end

  test "optional variable with a key" do
    %{ a: _a} <~ %{ c: 3}
    assert a == nil
  end

  test "optional variable in a list" do
    [ _e, f, g] <~ [ e: 1, f: 2, g: 3]
    assert e == 1
    assert f == 2
    assert g == 3
  end

  test "named key" do
    %{ a, b: %{ c: x}} <~ %{ a: 1, b: %{ c: 3}}
    assert a == 1
    assert x == 3
  end

  test "sole variable" do
    x <~ %{ a: 1}
    assert x == %{ a: 1}
  end

  test "sole variable match" do
    %{ a: a} = x <~ %{ a: 1}
    assert a == 1
    assert x == %{ a: 1}
  end

  test "sole variable assignment" do
    x = %{ a} <~ %{ a: 1}
    assert a == 1
    assert x == %{ a: 1}
  end

  test "sole variable destructure" do
    ( %{ a} = x) <~ %{ a: 1}
    assert a == 1
    assert x == %{ a: 1}
  end

  test "variable assignment within the match on the left" do
    x = %{ a: a = %{ b: b}} <~ %{ a: %{ b: 1}}
    assert b == 1
    assert a == %{ b: 1}
    assert x == %{ a: %{ b: 1}}
  end

  test "default values" do
    %{ a( 5), _b, _c( 7), d(), _e(), f: [ _x( 3), y]} <~ %{ c: 10, f: [ y: 7]}
    assert a == 5
    assert b == nil
    assert c == 10
    assert d == nil
    assert e == nil
    assert x == 3
    assert y == 7
  end

  test "map as a prevailing right side value" do
    %{ a( %{ a: 1})} <~ %{ a: %{ c: 1}}
    assert a == %{ c: 1}
  end

  test "map as a prevailing default value" do
    %{ a( %{ a: 1})} <~ %{}
    assert a == %{ a: 1}
  end

  test "list as a prevailing right side value" do
    %{ a( [ a: 1])} <~ %{ a: %{ c: 1}}
    assert a == %{ c: 1}
  end

  test "list as a prevailing default value" do
    %{ a( [ a: 1])} <~ %{}
    assert a == [ a: 1]
  end

  test "tuple as a prevailing right side value" do
    %{ a( { 1, 2, 3})} <~ %{ a: %{ c: 1}}
    assert a == %{ c: 1}
  end

  test "tuple as a prevailing default value" do
    %{ a( { 1, 2, 3})} <~ %{}
    assert a == { 1, 2, 3}
  end

  test "loose list size and order of elements 1" do
    [ c, _a, b] <~ [ b: 2, c: 3]
    assert a == nil
    assert b == 2
    assert c == 3
  end

  test "loose list size and order of elements 2" do
    [ d, b] <~ [ a: 1, b: 2, c: 3, d: 4, e: 5]
    assert d == 4
    assert b == 2
  end

  test "different tuple size and order of elements" do
    { c, a( 5), b} <~ { { :b, 2}, { :c, 3}}
    assert a == 5
    assert b == 2
    assert c == 3
  end

  test "implicit structural transformation" do
    %{ a, b: b = [ c, d, e: x = { f, g} = e]} <~ [ a: 1, b: %{ c: 3, d: 4, e: %{ f: 6, g: 7}, h: 10}]
    assert a == 1
    assert b == [ c: 3, d: 4, e: { { :f, 6}, { :g, 7}}]
    assert c == 3
    assert d == 4
    assert f == 6
    assert e == { { :f, 6}, { :g, 7}}
    assert g == 7
    assert x == { { :f, 6}, { :g, 7}}
  end

  test "matching other than assignment" do
    %{ a: %{ b: x} = %{ b}} <~ %{ a: [ b: 2]}
    assert b == 2
    assert x == 2
  end

  test "structure matching from loose to rigid and back" do
    %{ a, b: b = ^{ c, d, ^%{ e}}} <~ [ a: 1, b: { 3, 4, [ e: 5]}]
    assert a == 1
    assert b == { 3, 4, %{ e: 5}}
    assert c == 3
    assert d == 4
    assert e == 5
  end

  test "nested rigid two element tuple assigned to var" do
    [ a: a = ^{ b, c}] <~ %{ a: { 2, 3}}
    assert a == { 2, 3}
    assert b == 2
    assert c == 3
  end

  test "nested rigid two element tuple" do
    [ a: ^{ b, c}] <~ %{ a: { 2, 3}}
    assert b == 2
    assert c == 3
  end

  test "nested rigid other than two elements tuple" do
    [ a: ^{ b, c, d}] <~ %{ a: { 2, 3, 4}}
    assert b == 2
    assert c == 3
    assert d == 4
  end

  test "rigid list" do
    ^[ a, b] <~ [ 1, 2]
    assert a == 1
    assert b == 2
  end

  test "rigid keyword list" do
    ^[ a: a, b: b] <~ [ a: 1, b: 2]
    assert a == 1
    assert b == 2
  end

  test "fail rigid list when different size" do
    assert_raise MatchError, fn ->
      ^[ a, b] <~ [ a: 1, b: 2, c: 3]
      assert a == 1
      assert b == 2
    end
  end

  test "fail rigid keyword list when different size" do
    assert_raise MatchError, fn ->
      ^[ a, b] <~ [ a: 1, b: 2, c: 3]
      assert a == 1
      assert b == 2
    end
  end

  test "fail rigid keyword list when different order of elements" do
    assert_raise MatchError, fn ->
      ^[ b: b, a: a] <~ [ a: 1, b: 2]
      assert b == 2
      assert a == 1
    end
  end

  test "fail rigid list from map" do
    assert_raise MatchError, fn ->
      ^[ a, b] <~ %{ a: 1, b: 2}
      assert a == { :a, 1}
      assert b == { :b, 2}
    end
  end

  test "fail rigid list from tuple" do
    assert_raise MatchError, fn ->
      ^[ a, b] <~ { { :a, 1}, { :b, 2}}
      assert a == { :a, 1}
      assert b == { :b, 2}
    end
  end

  test "fail rigid map from list" do
    assert_raise MatchError, fn ->
      ^%{ a, b} <~ [ a: 1, b: 2]
      assert a == 1
      assert b == 2
    end
  end

  test "fail rigid map from tuple of pairs" do
    assert_raise MatchError, fn ->
      ^%{ a, b} <~ { { :a, 1}, { :b, 2}}
      assert a == 1
      assert b == 2
    end
  end

  test "rigid two element tuple from tuple" do
    ^{ a, b} <~ { 1, 2}
    assert a == 1
    assert b == 2
  end

  test "rigid other than two element tuple from tuple" do
    ^{ a, b, c} <~ { 1, 2, 3}
    assert a == 1
    assert b == 2
    assert c == 3
  end

  test "rigid tuple from tuple of pairs" do
    ^{ a, b} <~ { { :a, 1}, { :b, 2}}
    assert a == { :a, 1}
    assert b == { :b, 2}
  end

  test "fail rigid tuple from map" do
    assert_raise MatchError, fn ->
      ^{ a, b} <~ %{ a: 1, b: 1}
      assert a == 1
      assert b == 2
    end
  end

  test "fail rigid tuple from list" do
    assert_raise MatchError, fn ->
      ^{ a, b} <~ [ a: 1, b: 1]
      assert a == 1
      assert b == 2
    end
  end

  test "fail loose tuple from standard tuple" do
    assert_raise MatchError, fn ->
      { a, b} <~ { 1, 2}
      assert a == 1
      assert b == 2
    end
  end

  test "loose keyword list [ head | tail]" do
    [ a | rest] <~ [ a: 1, b: 2, c: 3]
    assert a == 1
    assert rest == [ b: 2, c: 3]
  end

  test "loose keyword list [ head | tail] arbitrary var" do
    [ b | rest] <~ [ a: 1, b: 2, c: 3]
    assert b == 2
    assert rest == [ a: 1, c: 3]
  end

  test "loose keyword list [ head | tail] from map" do
    [ b | rest] <~ %{ a: 1, b: 2, c: 3}
    assert b == 2
    assert rest[ :a] == 1
    assert rest[ :c] == 3
  end

  test "loose keyword list [ head | tail] from key-pair tuple" do
    [ b | [ a, c]] <~ { { :a, 1}, { :b, 2}, { :c, 3}}
    assert b == 2
    assert a == 1
    assert c == 3
  end

  test "loose keyword list [ head | [ head | tail]" do
    [ b | [ a | c]] <~ { { :a, 1}, { :b, 2}, { :c, 3}}
    assert b == 2
    assert a == 1
    assert c == [ c: 3]
  end

  test "loose keyword list structured head" do
    [ { :a, %{ b}} | %{ c, d}] <~ [ a: %{ b: 2}, c: 3, d: 4]
    assert b == 2
    assert c == 3
    assert d == 4
  end

  test "fail non-keyword list on the right side" do
    assert_raise MatchError, fn ->
      [ %{ a} | %{ c, d}] <~ [ [ a: 1], %{ c: 3, d: 4}]
      assert a == 1
      assert c == 3
      assert d == 4
    end
  end

  test "rigid list [ any head | any tail]" do
    ^[ a | rest] <~ [ 1, 2, 3]
    assert a == 1
    assert rest == [ 2, 3]
  end

  test "rigid list [ any head | tail structure]" do
    ^[ a | [ b, c]] <~ [ 1, 2, 3]
    assert a == 1
    assert b == 2
    assert c == 3
  end

  test "rigid list [ head structure | any tail]" do
    ^[ %{ a} | rest] <~ [ %{ a: 1}, c: 3, d: 4]
    assert a == 1
    assert rest == [ c: 3, d: 4]
  end

  test "rigid list [ head structure | tail structure]" do
    ^[ %{ a} | [ %{ c, d}]] <~ [ %{ a: 1}, %{ c: 3, d: 4}]
    assert a == 1
    assert c == 3
    assert d == 4
  end

  test "rigid list [ loose head structure | loose tail structure]" do
    ^[ ^[ a] | [ ^[ c, d]]] <~ [ %{ a: 1}, %{ c: 3, d: 4}]
    assert a == 1
    assert c == 3
    assert d == 4
  end

  test "loose empty map: transform whole structure into a map" do
    [ a: a = %{}] <~ [ a: [ b: 2, c: 3]]
    assert a == %{ b: 2, c: 3}

    a = %{} <~ [ d: 4, e: 5]
    assert a == %{ d: 4, e: 5}
  end

  test "loose non-empty map: transform whole structure ONLY if map" do
    [ a: a = %{ b}] <~ [ a: [ b: 2, c: 3]]
    assert a == %{ b: 2, c: 3}
    assert b == 2

    a = %{ e} <~ [ d: 4, e: 5]
    assert a == %{ d: 4, e: 5}
    assert e == 5
  end

  test "loose empty list: transform whole structure into a keyword list" do
    [ a: a = []] <~ [ a: %{ b: 2, c: 3}]
    assert a == [ b: 2, c: 3]

    a = [] <~ %{ d: 4, e: 5}
    assert a == [ d: 4, e: 5]
  end

  test "loose empty tuple: transform whole structure into a tuple of key pairs" do
    [ a: a = {}] <~ [ a: %{ b: 2, c: 3}]
    assert a == { { :b, 2}, { :c, 3}}

    a = {} <~ [ d: 4, e: 5]
    assert a == { { :d, 4}, { :e, 5}}
  end

  test "rigid empty map: take whole structure if map" do
    [ a: a = ^%{}] <~ [ a: %{ b: 2}]
    assert a == %{ b: 2}
  end

  test "rigid non-empty map: take whole structure ONLY if map" do
    [ a: a = ^%{ b}] <~ [ a: %{ b: 2, c: 3}]
    assert a == %{ b: 2, c: 3}
    assert b == 2
  end

  test "rigid empty map: fail if not a map" do
    assert_raise MatchError, fn ->
      [ a: ^%{}] <~ [ a: [ b: 2]]
    end
  end

  test "rigid empty list: take whole structure if list" do
    [ a: a = ^[]] <~ [ a: [ b: 2]]
    assert a == [ b: 2]
  end

  test "rigid empty list: fail if not a list" do
    assert_raise MatchError, fn ->
      [ a: ^[]] <~ [ a: %{ b: 2}]
    end
  end

  test "rigid empty tuple: take whole structure if tuple" do
    [ a: a = ^{}] <~ [ a: { 2}]
    assert a == { 2}
  end

  test "rigid empty tuple: fail if not a tuple" do
    assert_raise MatchError, fn ->
      [ a: ^{}] <~ [ a: [ b: 2]]
    end
  end

  test "destructure from a module structure" do
    %{ a, b} <~ %Foo{ a: 1, b: 2}
    assert a == 1
    assert b == 2

    [ a, b] <~ %Foo{ a: 3, b: 4}
    assert a == 3
    assert b == 4

    { a, b} <~ %Foo{ a: 5, b: 6}
    assert a == 5
    assert b == 6
  end

  test "destructure from a module structure and the structure itself" do
    [ x: x = %{ b}] <~ [ x: %Foo{ a: 1, b: 2}]
    assert b == 2
    assert x == %Foo{ a: 1, b: 2}
  end

  test "fail missing non optional variables in loose list" do
    assert_raise MatchError, fn ->
      [ a] <~ [ b: 1]
      assert a == nil
    end
  end

  test "fail missing non optional variables in loose tuple" do
    assert_raise MatchError, fn ->
      { a} <~ [ b: 1]
      assert a == nil
    end
  end

  test "pattern match rigid list with underscore variable" do
    ^[ a, _, _, d] <~ [ 1, 2, 3, 4]
    assert a == 1
    assert d == 4
  end

  test "pattern match rigid tuple with underscore variable" do
    ^{ a, _, _, d} <~ { 1, 2, 3, 4}
    assert a == 1
    assert d == 4
  end

  test "pattern match rigid tuple with the underscore variable within a loose structure" do
    [ a, _b, c: ^{ _, e}, f: f] <~ %{ a: 1, c: { 4, 5}, f: 6}
    assert a == 1
    assert b == nil
    assert e == 5
    assert f == 6
  end

  test "unspecified string keys" do
    @[ a] <~ %{ "a" => "1"}
    assert a == "1"
  end

  test "specified string key" do
    @[ x: a] <~ %{ "x" => "1"}
    assert a == "1"
  end

  test "atom/string key combo" do
    [ a: a = @%{ b, c: @[ d, e]}] <~ %{ a: [ { "b", "2"}, { "c", %{ d: 4, e: 5}}]}
    assert a == %{ "b" => "2", "c" => [ d: 4, e: 5]}
    assert b == "2"
    assert d == 4
    assert e == 5
  end

  test "string key in rigid mode" do
    @^%{ b} <~ %{ "b" => 2}
    assert b == 2
  end

  test "string key with a default value in rigid mode" do
    @^%{ a( 1)} <~ %{ "b" => 2}
    assert a == 1
  end

  test "fails string key in rigid mode when different structure type" do
    assert_raise MatchError, fn ->
      @^%{ a( 1)} <~ [ { "b", 2}]
      assert a == 1
    end
  end
end