with builtins;

# Non capturing regex returns empty lists
assert
  split "foobar" "foobar" == [
    ""
    [ ]
    ""
  ];
assert
  split "fo*" "f" == [
    ""
    [ ]
    ""
  ];
assert split "fo+" "f" == [ "f" ];
assert
  split "fo*" "fo" == [
    ""
    [ ]
    ""
  ];
assert
  split "fo*" "foo" == [
    ""
    [ ]
    ""
  ];
assert
  split "fo+" "foo" == [
    ""
    [ ]
    ""
  ];
assert
  split "fo{1,2}" "foo" == [
    ""
    [ ]
    ""
  ];
assert
  split "fo{1,2}" "fooo" == [
    ""
    [ ]
    "o"
  ];
assert
  split "fo*" "foobar" == [
    ""
    [ ]
    "bar"
  ];

# Capturing regex returns a list of sub-matches
assert
  split "(fo*)" "f" == [
    ""
    [ "f" ]
    ""
  ];
assert split "(fo+)" "f" == [ "f" ];
assert
  split "(fo*)" "fo" == [
    ""
    [ "fo" ]
    ""
  ];
assert
  split "(f)(o*)" "f" == [
    ""
    [
      "f"
      ""
    ]
    ""
  ];
assert
  split "(f)(o*)" "foo" == [
    ""
    [
      "f"
      "oo"
    ]
    ""
  ];
assert
  split "(fo+)" "foo" == [
    ""
    [ "foo" ]
    ""
  ];
assert
  split "(fo{1,2})" "foo" == [
    ""
    [ "foo" ]
    ""
  ];
assert
  split "(fo{1,2})" "fooo" == [
    ""
    [ "foo" ]
    "o"
  ];
assert
  split "(fo*)" "foobar" == [
    ""
    [ "foo" ]
    "bar"
  ];

# Matches are greedy.
assert
  split "(o+)" "oooofoooo" == [
    ""
    [ "oooo" ]
    "f"
    [ "oooo" ]
    ""
  ];

# Matches multiple times.
assert
  split "(b)" "foobarbaz" == [
    "foo"
    [ "b" ]
    "ar"
    [ "b" ]
    "az"
  ];

# Split large strings containing newlines. null are inserted when a
# pattern within the current did not match anything.
assert
  split "[[:space:]]+|([',.!?])" ''
    Nix Rocks!
    That's why I use it.
  '' == [
    "Nix"
    [ null ]
    "Rocks"
    [ "!" ]
    ""
    [ null ]
    "That"
    [ "'" ]
    "s"
    [ null ]
    "why"
    [ null ]
    "I"
    [ null ]
    "use"
    [ null ]
    "it"
    [ "." ]
    ""
    [ null ]
    ""
  ];

# Documentation examples
assert
  split "(a)b" "abc" == [
    ""
    [ "a" ]
    "c"
  ];
assert
  split "([ac])" "abc" == [
    ""
    [ "a" ]
    "b"
    [ "c" ]
    ""
  ];
assert
  split "(a)|(c)" "abc" == [
    ""
    [
      "a"
      null
    ]
    "b"
    [
      null
      "c"
    ]
    ""
  ];
assert
  split "([[:upper:]]+)" "  FOO   " == [
    "  "
    [ "FOO" ]
    "   "
  ];

true