ona/src/mem.zig

const std = @import("std");

///
/// State machine for lazily computing all components of [Spliterator.source] that match the pattern
/// in [Spliterator.delimiter].
///
pub fn Spliterator(comptime Element: type) type {
    return struct {
        source: []const Element,
        delimiter: []const Element,

        const Self = @This();

        ///
        /// Returns `true` if there is more data to be processed, otherwise `false`.
        ///
        /// Note that [Spliterator.next] implicitly calls this function to determine if it should
        /// return another slice or `null`.
        ///
        pub fn hasNext(self: Self) bool {
            return (self.source.len != 0);
        }

        ///
        /// Iterates on `self` and returns the next view of [Spliterator.source] that matches
        /// [Spliterator.delimiter], or `null` if there is no more data to be processed.
        ///
        pub fn next(self: *Self) ?[]const Element {
            if (self.delimiter.len == 0) {
                defer self.source = self.source[self.source.len .. 0];

                return self.source;
            }

            while (self.hasNext()) {
                var cursor = @as(usize, 0);
                var window = self.source[cursor .. (self.source.len - cursor)];

                defer self.source = window;

                if (std.mem.eql(Element, window, self.delimiter))
                    return self.source[cursor .. self.delimiter.len];
            }

            return null;
        }
    };
}

///
/// Searches the slice of `Data` referenced by `data` for the first instance of `sought_datum`,
/// returning its index or `null` if it could not be found.
///
pub fn findFirst(comptime Data: type, data: []const Data, sought_datum: Data) ?usize {
    for (data) |datum, index| if (datum == sought_datum) return index;

    return null;
}