/// Slice returns a subsection of an array.
Slice :: (view: []$T, start_idx: int, count := -1, loc := #caller_location) -> []T {
   AssertCallsite(start_idx >= +0 && start_idx < view.count, "incorrect slice bounds");
   AssertCallsite(count >= -1 && count < view.count, "incorrect slice length");

   if count == -1
    { count = view.count - start_idx; }

   return .{ data = view.data + start_idx, count = count };
}

/// Reset sets an array's length to 0, allowing it to be reused
/// without allocating new memory.
Reset :: (view: *[]$T) {
   view.count = 0;
}

/// Clear zeroes the memory of an array and sets its length to 0.
///
/// Note: Clear does not free the array's memory.
Clear :: (view: *[]$T) {
   MemZero(view.data, view.count * size_of(T));
   view.count = 0;
}

/// Equal checks the equality of two arrays.
Equal :: (lhs: []$T, rhs: []T) -> bool {
   if lhs.count != rhs.count
    { return false; }
   return MemEqual(lhs.data, rhs.data, lhs.count * size_of(T));
}


FindFlags :: enum_flags {
   Last;    // Return the last matching element.
   FromEnd; // Search in reverse.
}

FindResult :: struct(T: Type) {
   value: T = ---;
   index: int;
}

/// Find searches through an array, returning the first element
/// that matches the given value.
Find :: (view: []$T, value: T, $flags: FindFlags = 0) -> (bool, FindResult(T)) {
   found: bool;

   result: FindResult(T);
   result.index = -1;

   REVERSE :: #run (flags & .FromEnd).(bool);
   for #v2 <=REVERSE view if it == value {
      found  = true;
      result.index = it_index;
      result.value = it;
      #if !(flags & .Last) break;
   }

   return found, result;
}

/// Contains checks if the given value exists in an array.
Contains :: (view: []$T, value: T) -> bool {
   return Find(view, value);
}


TrimFlags :: enum_flags {
   FromStart;   // Trim the start of the array.
   FromEnd;     // Trim the end of the array.
   MatchInFull; // Only trim when the cutset matches exactly.
}

/// Trim returns a subsection of an array with all leading/trailing values
/// from cutset removed.
Trim :: (view: []$T, cutset: []T, $flags: TrimFlags = .FromStart) -> []T {
   result := view;
   if cutset.count == 0 || cutset.count > view.count {
      return result;
   }

   #if flags & .FromStart {
      #if flags & .MatchInFull {
         if Equal(Slice(view, 0, cutset.count), cutset) {
            result = Slice(view, cutset.count, -1);
         }
      }
      else {
         while result.count > 0 {
            if !Contains(cutset, result[0]) {
               break;
            }

            result.data  += 1;
            result.count -= 1;
         }
      }
   }

   #if flags & .FromEnd {
      #if flags & .MatchInFull {
         if Equal(Slice(view, view.count - cutset.count), cutset) {
            result.count -= cutset.count;
         }
      }
      else {
         while result.count > 0 {
            if !Contains(cutset, result[result.count - 1]) {
               break;
            }

            result.count -= 1;
         }
      }
   }

   return result;
}


#scope_file

#if #exists(RunTests) #run,stallable {
   Test("slice", t => {
      a1 := int.[ 1, 2, 3, 4, 5 ];
      a2 := Slice(a1, 2);
      Expect(a2.count == 3);
      Expect(Equal(a2, int.[ 3, 4, 5 ]));

      b1 := int.[ 1, 2, 3, 4, 5 ];
      b2 := Slice(b1, 2, 0);
      Expect(b2.count == 0);
      Expect(b2.data  == b1.data + 2);

      c1 := int.[ 1, 2, 3, 4, 5 ];
      c2 := Slice(c1, 3, 1);
      Expect(c2.count == 1);
      Expect(Equal(c2, int.[ 4 ]));

      d1 := int.[ 1, 2, 3 ];
      d2 := Slice(d1, 2);
      Expect(d2.count == 1);
      Expect(Equal(d2, int.[ 3 ]));
   });

   Test("find", t => {
      a := int.[ 1, 2, 3, 4, 5 ];

      ok, res := Find(a, 3);
      Expect(ok && res.index == 2);
      Expect(res.value == 3);

      ok, res = Find(a, -1);
      Expect(!ok && res.index == -1);

      b := int.[ 1, 2, 2, 3, 4, 5, 2 ];

      ok, res = Find(b, 2);
      Expect(ok && res.index == 1);

      ok, res = Find(b, 2, .FromEnd);
      Expect(ok && res.index == 6);

      c := int.[ 0, 0, 0, 1, 2, 3, 0, 0, 0 ];

      ok, res = Find(c, 0, .Last);
      Expect(ok && res.index == 8);

      ok, res = Find(c, 0, .FromEnd | .Last);
      Expect(ok && res.index == 0);
   });

   Test("contains", t => {
      a := int.[ 1, 2, 3, 4, 5 ];
      Expect(Contains(a, 3));
      Expect(!Contains(a, -1));
   });

   Test("trim", t => {
      a1 := int.[ 0, 0, 0, 1, 2, 3 ];
      a2 := Trim(a1, .[ 0 ]);
      Expect(Equal(a1, .[ 0, 0, 0, 1, 2, 3 ]));
      Expect(Equal(a2, .[ 1, 2, 3 ]));

      b1 := int.[ 0, 0, 0, 1, 2, 3, 0, 0, 0 ];
      b2 := Trim(b1, .[ 0 ], .FromEnd);
      Expect(Equal(b1, .[ 0, 0, 0, 1, 2, 3, 0, 0, 0 ]));
      Expect(Equal(b2, .[ 0, 0, 0, 1, 2, 3 ]));

      c1 := int.[ 0, 0, 0, 1, 2, 3, 0, 0, 0 ];
      c2 := Trim(c1, .[ 0 ], .FromStart | .FromEnd);
      Expect(Equal(c1, .[ 0, 0, 0, 1, 2, 3, 0, 0, 0 ]));
      Expect(Equal(c2, .[ 1, 2, 3 ]));

      d1 := int.[ 0, 0, 0, 1, 2, 3, 0, 0, 0 ];
      d2 := Trim(d1, .[ 0, 0, 0 ], .FromStart | .MatchInFull);
      d3 := Trim(d1, .[ 0, 0, 0 ], .FromEnd   | .MatchInFull);
      d4 := Trim(d1, .[ 0, 0, 0 ], .FromStart | .FromEnd | .MatchInFull);
      Expect(Equal(d1, .[ 0, 0, 0, 1, 2, 3, 0, 0, 0 ]));
      Expect(Equal(d2, .[ 1, 2, 3, 0, 0, 0 ]));
      Expect(Equal(d3, .[ 0, 0, 0, 1, 2, 3 ]));
      Expect(Equal(d4, .[ 1, 2, 3 ]));
   });
}