// list helper functions
// 0.9.3 -- "list()" now deprecated in favor of "zip()".
// 0.9.5 -- "zip()" now deprecated as well: single-pair lists are handled automatically

@function list($args...) {
  $output: ();
  @each $arg in $args { $output: append($output, $arg, 'comma'); }
  @return $output;
}
@function slice($list, $start: 1, $end: length($list), $sep: 'comma') {
  $output: ();
  @for $i from $start through $end {
    $output: append($output, nth($list, $i), $sep); }
  @return $output;
}
@function set-nth($list, $index, $value, $sep: 'comma') {
  $length: length($list); $output: ();
  @if $index > $length or $index <= 0 { @return $list; }
  @if $index > 1 { @for $i from 1 through $index - 1 { $output: append($output, nth($list, $i), $sep); } }
  $output: append($output, $value, $sep);
  @if $length > 1 { @for $i from $index + 1 through $length { $output: append($output, nth($list, $i), $sep); } }
  @return $output;
}

// list-map helper functions
// 0.9.3 -- key() and value() tentatively added as alternatives to 'tuple-' named funcs
// 0.9.6 -- added better error handling; aliased to single version of each

@function tuple-key($tuple) { @if length($tuple) < 1 { @return null; } @else { @return nth($tuple, 1); } }
@function tuple-value($tuple) { @if length($tuple) < 2 { @return null; } @else { @return nth($tuple, 2); } }
@function key($tuple) { @return tuple-key($tuple); }
@function value($tuple) { @return tuple-value($tuple); }

// 0.9.5 -- added list-map-check()

@function list-map-check($list) { @if length($list) == 2 and length(nth($list, 1)) == 1 { @return append((), $list, 'comma'); } @return $list; }

// list-map versions of list-map-keys(), -values() and -has-key() functions
// 0.9.5 -- now all handle single- or double-wrapped list-maps (single-pair case) automatically
// 0.9.5 -- added map-prev-key() and map-next-key() functions

@function map-keys($list...) {
  @if length($list) == 1 { $list: list-map-check($list...); }
  @else { $list: list-map-check($list); } $output: ();
  @each $tuple in $list { $output: append($output, tuple-key($tuple), 'comma'); }
  @return $output;
}
@function map-values($list...) {
  @if length($list) == 1 { $list: list-map-check($list...); }
  @else { $list: list-map-check($list); } $output: ();
  @each $tuple in $list { $output: append($output, tuple-value($tuple), 'comma'); }
  @return $output;
}
@function map-has-key($list, $key) {
  $list: list-map-check($list);
  @each $tuple in $list { @if tuple-key($tuple) == $key { @return true; } }
  @return false;
}
@function map-prev-key($list, $key) {
  $list: list-map-check($list); $keys: map-keys($list);
  @return nth($keys, index($keys, $key) - 1);
}
@function map-next-key($list, $key) {
  $list: list-map-check($list); $keys: map-keys($list);
  @return nth($keys, index($keys, $key) + 1);
}

// list-map versions of list-map-get(), -merge() and -remove()
// 0.9.5 -- list-map-check() has been integrated to handle single-pair inputs, and give correct outputs

@function map-get($list, $key, $check: true) {
  @if $check { $list: list-map-check($list); } @each $tuple in $list {
    @if tuple-key($tuple) == $key { @return list-map-check(tuple-value($tuple)); } }
   // @if tuple-key($tuple) == $key { @return list-map-check($tuple); } }
  @return null;
}
@function map-merge($list1, $list2, $check: true) {
  @if $check { $list1: list-map-check($list1); $list2: list-map-check($list2); }
  $keys1: map-keys($list1);
  @each $tuple in $list2 {
    $index: index($keys1, tuple-key($tuple));
    @if $index { $list1: set-nth($list1, $index, $tuple); }
    @else { $list1: append($list1, $tuple, 'comma'); } }
  @return $list1;
}
@function map-remove($list, $key) {
  $list: list-map-check($list);
  $keys: map-keys($list); $output: ();
  @for $n from 1 through length($list) {
    @if nth($keys, $n) != $key { $output: append($output, nth($list, $n), 'comma'); } }
  @return $output;
}

// deep/nested map functions: list-map-get-z() and list-map-merge-z()
// 0.9.5 -- list-map-check() has been integrated, implicitly or explicitly

@function map-get-z($list, $keys...) {
  @if $list == null { @return null; }
  $length: length($keys);
  $list: map-get($list, nth($keys, 1));
  @if $length > 1 {
    @for $n from 2 through $length {
      @if $list == null { @return null; }
      $list: map-get($list, nth($keys, $n), false); }
    @return $list; }
  @else { @return $list; }
}
@function map-merge-z($list, $keys-and-value...) {
  $arg-length: length($keys-and-value);
  $value: nth($keys-and-value, $arg-length);
  $key-length: $arg-length - 1;
  $list: list-map-check($list);
  @if $key-length == 0 {
    $value: if(type-of($value) == 'list', map-merge($list, list-map-check($value), false), map-merge($list, append((), $value (), 'comma'), false)); }
  @else { $start: 1; @if type-of($value) == 'list' { $start: 0; $value: list-map-check($value); }
    @for $i from $start through $key-length {
      $new-list: (); $old-list: ();
      @if $i == 0 { $new-list: $value; } @else { $new-list: append((), nth($keys-and-value, $key-length + 1 - $i) $value, 'comma'); }
      @if $i == $key-length { $old-list: $list; } @else { $old-list: map-get-z($list, slice($keys-and-value, 1, $key-length - $i)...) or (); }
      $value: map-merge($old-list, $new-list); } }
  @return $value;
}

// aliases added as of 0.9.2: unify and replace map-*() and map-*-z() variants

@function get($args...) { @return map-get-z($args...); }
@function merge($args...) { @return map-merge-z($args...); }
@function set($args...) { @return map-merge-z($args...); }

// new as of 0.9.5: map-inspect()

@function map-inspect($list...) {
  @if length($list) == 1 { $list: list-map-check($list...); }
  @else { $list: list-map-check($list); }
  $output: '('; $i: 1;
  @each $tuple in $list {
    @if length($tuple) != 2 {
      $output: $output + '#{$tuple}'; }
    @else {
      $key: nth($tuple, 1);
      $value: nth($tuple, 2);
      @if type-of($value) == 'list' { $output: $output + '#{$key} #{map-inspect($value)}'; }
      @else { $output: $output + '#{$key} #{$value}'; } }
    @if $i < length(map-keys($list)) { $output: $output + ', '; }
    $i: $i + 1;
  }
  @return $output + ')';
}

// new as of 0.9.9: map-pretty()
$cr: '
';
$tab: '  ';
@function map-pretty($list, $level: 1) {
  @if length($list) == 1 { $list: list-map-check($list...); }
  @else { $list: list-map-check($list); }
  $indent: $tab; $outdent: $tab;
  @for $n from 1 through $level { $indent: $indent + $tab; }
  @for $n from 1 through $level - 1 { $outdent: $outdent + $tab; }
  $output: '(' + $cr + $indent; $i: 1;
  @each $tuple in $list {
    @if length($tuple) != 2 {
      $output: $output + '#{$tuple}'; }
    @else {
      $key: nth($tuple, 1); $value: nth($tuple, 2);
      @if type-of($value) == 'list' { $output: $output + '#{$key} #{map-pretty($value, $level+1)}'; }
      @else { $output: $output + '#{$key} #{$value}'; } }
    @if $i < length(map-keys($list)) { $output: $output + ',' + $cr + $indent; }
    $i: $i + 1;
  }
  // @return unquote($output + $cr + $outdent + ')'); // replace last line with this one for unquoted output in libsass
  @return $output + $cr + $outdent + ')';
}
// aliases of above
@function map-inspect-pretty($list...) { @return map-pretty($list...); }
@function map-inspect-p($list...) { @return map-pretty($list...); }