Arafatk/DataViz

package containers

// IteratorWithIndex is stateful iterator for ordered containers whose values can be fetched by an index.
type IteratorWithIndex interface {
    // Next moves the iterator to the next element and returns true if there was a next element in the container.
    // If Next() returns true, then next element's index and value can be retrieved by Index() and Value().
    // If Next() was called for the first time, then it will point the iterator to the first element if it exists.
    // Modifies the state of the iterator.
    Next() bool

    // Value returns the current element's value.
    // Does not modify the state of the iterator.
    Value() interface{}

    // Index returns the current element's index.
    // Does not modify the state of the iterator.
    Index() int

    // Begin resets the iterator to its initial state (one-before-first)
    // Call Next() to fetch the first element if any.
    Begin()

    // First moves the iterator to the first element and returns true if there was a first element in the container.
    // If First() returns true, then first element's index and value can be retrieved by Index() and Value().
    // Modifies the state of the iterator.
    First() bool
}

// IteratorWithKey is a stateful iterator for ordered containers whose elements are key value pairs.
type IteratorWithKey interface {
    // Next moves the iterator to the next element and returns true if there was a next element in the container.
    // If Next() returns true, then next element's key and value can be retrieved by Key() and Value().
    // If Next() was called for the first time, then it will point the iterator to the first element if it exists.
    // Modifies the state of the iterator.
    Next() bool

    // Value returns the current element's value.
    // Does not modify the state of the iterator.
    Value() interface{}

    // Key returns the current element's key.
    // Does not modify the state of the iterator.
    Key() interface{}

    // Begin resets the iterator to its initial state (one-before-first)
    // Call Next() to fetch the first element if any.
    Begin()

    // First moves the iterator to the first element and returns true if there was a first element in the container.
    // If First() returns true, then first element's key and value can be retrieved by Key() and Value().
    // Modifies the state of the iterator.
    First() bool
}

// ReverseIteratorWithIndex is stateful iterator for ordered containers whose values can be fetched by an index.
//
// Essentially it is the same as IteratorWithIndex, but provides additional:
//
// Prev() function to enable traversal in reverse
//
// Last() function to move the iterator to the last element.
//
// End() function to move the iterator past the last element (one-past-the-end).
type ReverseIteratorWithIndex interface {
    // Prev moves the iterator to the previous element and returns true if there was a previous element in the container.
    // If Prev() returns true, then previous element's index and value can be retrieved by Index() and Value().
    // Modifies the state of the iterator.
    Prev() bool

    // End moves the iterator past the last element (one-past-the-end).
    // Call Prev() to fetch the last element if any.
    End()

    // Last moves the iterator to the last element and returns true if there was a last element in the container.
    // If Last() returns true, then last element's index and value can be retrieved by Index() and Value().
    // Modifies the state of the iterator.
    Last() bool

    IteratorWithIndex
}

// ReverseIteratorWithKey is a stateful iterator for ordered containers whose elements are key value pairs.
//
// Essentially it is the same as IteratorWithKey, but provides additional:
//
// Prev() function to enable traversal in reverse
//
// Last() function to move the iterator to the last element.
type ReverseIteratorWithKey interface {
    // Prev moves the iterator to the previous element and returns true if there was a previous element in the container.
    // If Prev() returns true, then previous element's key and value can be retrieved by Key() and Value().
    // Modifies the state of the iterator.
    Prev() bool

    // End moves the iterator past the last element (one-past-the-end).
    // Call Prev() to fetch the last element if any.
    End()

    // Last moves the iterator to the last element and returns true if there was a last element in the container.
    // If Last() returns true, then last element's key and value can be retrieved by Key() and Value().
    // Modifies the state of the iterator.
    Last() bool

    IteratorWithKey
}