#include "./filtered_string_view.h"

#include <catch2/catch.hpp>

// Specification: 2.3 - Static Data Members
// Purpose: Ensure that the default predicate function returns true for any
// 			character passed in.
// Expected: The function should always return true for all possible arguments.
// Note: Taken directly from the specification, modified for catch2.
TEST_CASE("default predicate function always returns true") {
	const auto min = std::numeric_limits<char>::min();
	const auto max = std::numeric_limits<char>::max();
	for (char c = min; c != max; c++) {
		REQUIRE(fsv::filtered_string_view::default_predicate(c));
	}
}

// Specification: 2.4.1 - Default Constructor
// Purpose: Determine that the default constructor results in the equivalent
//          of an empty string.
// Expected: The view should compare equal to an empty string with a zero
//           length. Data should be set to nullptr.
// Note: We cannot test where the underlying predicate points to directly as
// 		 this would make the test brittle by introducing implementation details.
//       We may only test this implicitly via string comparisons.
TEST_CASE("default constructed is equivalent to an empty string") {
	const auto view = fsv::filtered_string_view{};
	REQUIRE(std::string{""} == view);
	REQUIRE(std::size(view) == 0);
	REQUIRE(std::data(view) == nullptr);
}

// Specification: 2.4.2 - Implicit String Constructor
// Purpose: Ensure the implicit string constructor does not modify the string it
// 			originally refers to or filter the data. It has not been provided
//          with an alternative predicate, so it should perform no filtering.
// Expected: The view should be equivalent to the parent string. Data should
// point directly to the parent string. The length should be equal to the parent
// string.
TEST_CASE("implicit string constructor is equivalent to parent string") {
	const auto parent = std::string{"parent string"};
	const auto view = fsv::filtered_string_view{parent};

	REQUIRE(parent == view);
	REQUIRE(std::data(parent) == std::data(view));
	REQUIRE(std::size(parent) == std::size(view));
};

// Specification: 2.4.3 - String Constructor with Predicate
// Purpose: The string constructor with a supplied predicate should filter the
// 			original string by the rules provided by the predicate.
// Expected: The view should NOT be equivalent to the parent string. The lengths
// 			 should not be identical. This is provided that the predicate
// 			 filters part of the original string.
TEST_CASE("string constructor with predicate filters parent string") {
	const auto parent = std::string{"parent string"};
	const auto view = fsv::filtered_string_view{parent, [](const char& c) { return c != 's'; }};
	REQUIRE(view == std::string{"parent tring"});
	REQUIRE(std::data(parent) == std::data(view));
	REQUIRE(std::size(parent) != std::size(view));
};

// Specification: 2.4.4 - Implicit Null-Terminated String Constructor
// Purpose: The implicit null terminated string constructor should perform
// 			identically to the standard string constructor.
// Expected: The view should be equivalent to the parent string in data, length
//           and equality.
TEST_CASE("implicit null terminated string does not filter parent string") {
	const auto parent = std::string{"parent string"};
	const auto view = fsv::filtered_string_view{parent.c_str()};
	REQUIRE(view == parent);
	REQUIRE(std::data(parent) == std::data(view));
	REQUIRE(std::size(parent) == std::size(view));
};

// Specification: 2.4.5 - Null-Terminated String with Predicate Constructor
// Purpose: The null terminated string with predicate constructor should operate
//			identically to the standard string constructor with a predicate.
//			Given a predicate, it should filter the string via that rule.
// Expected: The view should not be equivalent to the parent string. Data should
// 			 remain the same, while size should be different.
TEST_CASE("null-terminated string with predicate constructor filters the parent string") {
	const auto parent = std::string{"parent string"};
	const auto view = fsv::filtered_string_view{parent.c_str(), [](const char& c) { return c != 's'; }};
	REQUIRE(view == std::string{"parent tring"});
	REQUIRE(std::data(parent) == std::data(view));
	REQUIRE(std::size(parent) != std::size(view));
}

// Specification: 2.4.6 - Copy and Move Constructors
// Purpose: Copy constructors function as expected. In addition, the copy
//  		constructor has an equality constraint.
// Expected: The newly constructed object must compare equal to the copied
// 			 object.
// Note: This test was taken from the specification, modified for catch2. We
// 		 split the test into two for readability (the move constructor is
// 		 separate), and include additional length and non std::data equality
//       tests.
TEST_CASE("copy constructors compare equal") {
	const auto parent = fsv::filtered_string_view{"parent string"};
	const auto copy = parent;

	REQUIRE(std::data(copy) == std::data(parent));
	REQUIRE(copy == parent);
	REQUIRE(std::size(copy) == std::size(parent));
}

// Specification: 2.4.6 - Copy and Move Constructors
// Purpose: Copy and move constructors function as expected. In addition, the
// 			copy and move constructors have a number of constraints supplied by
//    		the specification.
// Expected: The move constructor should default construct the moved-from object,
// 		 	 while the new object should be identical to the original object.
TEST_CASE("move constructor is identical to moved from object before move") {
	const auto parent = fsv::filtered_string_view{"parent string"};
	auto copy = parent;

	const auto move = std::move(copy);
	REQUIRE(std::data(copy) == nullptr);
	REQUIRE(copy == fsv::filtered_string_view{});
}

// Specification: 2.5.2 - Copy Assignment
// Purpose: Copy assignment should copy at least the length, data and predicate
// of other such that the they compare equal via operator==.
// Expected: The view targeted by the copy assignment should compare equal to
// 			 the parent view.
// Notes: Copied from the specification, modified for catch2.
TEST_CASE("copy assignment passes equality comparison to parent object") {
	const auto parent = fsv::filtered_string_view{"42 bro", [](const char& c) { return c == '4' || c == '2'; }};
	auto copy = fsv::filtered_string_view{};
	copy = parent;
	REQUIRE(copy == parent);
}

// Specification: 2.5.2 - Copy Assignment
// Purpose: Copy assignment should not modify itself when self copied.
// Expected: Copy remains identical despite a self-copy.
TEST_CASE("copy assignment should not change object if self copied") {
	auto parent = fsv::filtered_string_view{"42 bro", [](const char& c) { return c == '4' || c == '2'; }};
	const auto copy = parent; // We copy here so we keep the previous information.
	parent = parent;
	REQUIRE(copy == parent);
}

// Specification 2.5.3 - Move Assignment
// Purpose: A moved from object should be left in a valid state equal to a
// 			default constructed view. In addition, the move should move the
//          contents of the old view to the new view.
// Expected: The moved from object is default constructed, while the new object
// 			 should be identical to the parent view.
TEST_CASE("move assignment should transfer contents and default construct moved") {
	auto parent = fsv::filtered_string_view{"'89 baby", [](const char& c) { return c == '8' || c == '9'; }};

	// Copy parent before the move so we can check the move consists of this.
	const auto copy = parent;

	auto move = fsv::filtered_string_view{};
	move = std::move(parent);
	REQUIRE(std::data(move) == std::data(copy));
	REQUIRE(move == copy);
	REQUIRE(std::size(move) == std::size(copy));

	// Ensure default construction.
	REQUIRE(std::size(parent) == 0);
	REQUIRE(std::data(parent) == nullptr);
}

// Specification 2.5.3 - Move Assignment
// Purpose: Move assignment should not modify itself when self moved.
// Expected: Move remains identical despite a self-move.
TEST_CASE("move assignment should not change object if self copied") {
	auto parent = fsv::filtered_string_view{"42 bro", [](const char& c) { return c == '4' || c == '2'; }};
	const auto copy = parent; // We copy here so we keep the previous information.
	parent = std::move(parent);
	REQUIRE(copy == parent);
}

// Specification 2.5.4 - Subscript
// Purpose: Test if we can read the string given a specific subscript. We supply
// 			a predicate which filters some data so we can read into a view.
// Expected: The subscript is equal to the expected characters, filtering out
//           those defined by the predicate.
TEST_CASE("subscript should be affected by view predicate") {
	const auto parent = fsv::filtered_string_view("123", [](const char& c) { return c != '2'; });
	REQUIRE(parent[0] == '1');
	REQUIRE(parent[1] == '3');
}

// Specification 2.5.5 - String Type Conversion
// Purpose: We should be able to convert a view back into a string. Filtered out
// 			data should be removed, as if we were looking at the view.
// Expected: The view converted into a string should return a string affected by
//			 the predicate.
TEST_CASE("string conversion should be affected by view predicate") {
	const auto parent = fsv::filtered_string_view{"123", [](const char& c) { return c != '2'; }};
	REQUIRE(static_cast<std::string>(parent) == "13");
}

// Specification 2.5.5 - String Type Conversion
// Purpose: A string conversion should be a copy of the underlying data.
// Expected: The data pointer to the view should be different to the new string.
TEST_CASE("string conversion should return a new string") {
	const auto parent = fsv::filtered_string_view{"123", [](const char& c) { return c != '2'; }};
	const auto s = static_cast<std::string>(parent);
	REQUIRE(std::data(s) != std::data(parent));
}

// Specification: 2.6.1 - At
// Purpose: At performs bounds checking of a filtered string. We ensure at performs
// 			identically to subscript operators, unless we read out of bounds, in
//			which case it throws.
// Expected: The view should return expected at results, similar to subscript.
TEST_CASE("at should be affected by view predicate") {
	const auto parent = fsv::filtered_string_view{"123", [](const char& c) { return c != '2'; }};
	REQUIRE(parent.at(0) == '1');
	REQUIRE(parent.at(1) == '3');
}

// Specification: 2.6.1 - At
// Purpose: At should throw on an out of bounds read, negative or positive, with
//			a specific message and std::domain_error.
// Expected: The view should throw if we read outside of size().
TEST_CASE("at should throw on out of bounds reads") {
	const auto parent = fsv::filtered_string_view{"123", [](const char& c) { return c != '2'; }};
	REQUIRE_THROWS_AS(parent.at(-1), std::domain_error);
	REQUIRE_THROWS_WITH(parent.at(-1), "filtered_string_view::at(-1): invalid index");
	REQUIRE_THROWS_WITH(parent.at(2), "filtered_string_view::at(2): invalid index");
	REQUIRE_THROWS_AS(parent.at(2), std::domain_error);
}

// Specification: 2.6.2 - Size
// Purpose: Size should be equal to the size of the parent string with no pred.
// Expected: The string size should be equal to the view size with no predicate.
TEST_CASE("size should be equal to the parent string with no predicate") {
	const auto parent = fsv::filtered_string_view{"Maltese"};
	REQUIRE(std::size(parent) == 7);
}

// Specification: 2.6.2 - Size
// Purpose: Size should be equal to the size of the filtered string.
// Expected: The string size should be equal to the amount of times the predicate
// 			 returned true for that parent string.
TEST_CASE("size should be affected by view predicate") {
	const auto parent = fsv::filtered_string_view{"Maltese", [](const char& c) { return c == 'a' or c == 'e'; }};
	REQUIRE(std::size(parent) == 3);
}

// Specification: 2.6.3 - Empty
// Purpose: Empty should return true when the size of the view is zero.
// Expected: An empty view should return true. A non-empty view should return
// 			 false.
TEST_CASE("empty should return true when size is zero, and false when nonzero") {
	REQUIRE(fsv::filtered_string_view{}.empty() == true);
	REQUIRE(fsv::filtered_string_view{"1"}.empty() == false);
}

// Specification: 2.6.3 - Empty
// Purpose: Empty should return true when the view with predicate results in an
// 			empty string.
// Expected: The 'viewed' string with a false predicate should always return true.
TEST_CASE("empty should return true when predicate filters all characters") {
	const auto parent = fsv::filtered_string_view{"non_empty", [](const char&) { return false; }};
	REQUIRE(parent.size() == 0);
	REQUIRE(parent.empty() == true);
}

// Specification: 2.6.3 - Data
// Purpose: Data should return the owned string, without an affected filter.
// Expected: The data of a string view should not be affected by the predicate,
//			 so should be equal to the parent string despite the predicate.
TEST_CASE("data should not be affected by the predicate") {
	const auto parent = std::string{"chars"};
	const auto view = fsv::filtered_string_view{parent, [](const char&) { return false; }};
	REQUIRE(std::string{std::data(view)} == parent);
}

// Specification: 2.6.3 - Predicate
// Purpose: The predicate method should return the predicate passed in any
//			constructor.
// Expected: The effects of a function should passed to the view should be made
//			 when calling the function provided by the predicate method.
TEST_CASE("predicate returns the same function during construction") {
	int count = 0;
	const auto view = fsv::filtered_string_view{"", [&](const char&) {
		                                            ++count;
		                                            return true;
	                                            }};

	// We don't know how many times predicate calls the original function, so we
	// store the result of count after the constructor.
	const auto before_call = count;

	view.predicate()(char{});
	REQUIRE(before_call + 1 == count);
}

// Specification: 2.7.1 - Equality Comparison
// Purpose: Ensure that the predicate affects the result of the equality
//   	    comparison.
// Expected: Equality should be true when the predicate results in two
// functionally identical views of strings regardless of its data.
TEST_CASE("equality comparison is true when affected by predicate") {
	const auto view1 = fsv::filtered_string_view{"bca", [](const char& c) { return c == 'a'; }};
	const auto view2 = fsv::filtered_string_view{"abc", [](const char& c) { return c == 'a'; }};
	REQUIRE(view1 == view2);
}

// Specification: 2.7.1 - Equality Comparison
// Purpose: Ensure that the predicate affects the result of the equality
//   	    comparison.
// Expected: Equality should be false when the predicate differs on the same
// 		   	 string and produces different results through the view.
TEST_CASE("equality comparison is false when affected by predicate") {
	const auto parent = std::string{"abc"};
	const auto view1 = fsv::filtered_string_view{parent, [](const char& c) { return c == 'a'; }};
	const auto view2 = fsv::filtered_string_view{parent, [](const char& c) { return c == 'b'; }};
	REQUIRE(not(view1 == view2));
}

// Specification: 2.7.1 - Equality Comparison
// Purpose: Ensure that inequality functions as expected.
// Expected: Equality should be the inverse of inequality.
TEST_CASE("inequality is the inverse of equality") {
	const auto view1 = fsv::filtered_string_view{"bca", [](const char& c) { return c == 'a'; }};
	const auto view2 = fsv::filtered_string_view{"abc", [](const char& c) { return c == 'a'; }};
	REQUIRE(view1 == view2);
	REQUIRE(not(view1 != view2));
}

// Specification: 2.7.2 - Relational Comparison
// Purpose: Ensure that relational comparisons functions as expected.
// Expected: Relational comparisons should be logically consistent.
// Note: Test copied from the specification, modified for catch2.
TEST_CASE("relational comparison is logically consistent") {
	const auto lo = fsv::filtered_string_view{"aaa"};
	const auto hi = fsv::filtered_string_view{"zzz"};

	REQUIRE(lo < hi);
	REQUIRE(lo <= hi);
	REQUIRE(not(lo > hi));
	REQUIRE(not(lo >= hi));
	REQUIRE(lo <=> hi == std::strong_ordering::less);
}

// Specification: 2.7.2 - Relational Comparison
// Purpose: Ensure that relational comparisons functions are affected by the
// 			predicate.
// Expected: Relational comparisons should use the result of the view, not the
//			 source string.
TEST_CASE("relational comparison is affected by predicate") {
	const auto lo = fsv::filtered_string_view{"za", [](const auto& c) { return c != 'z'; }};
	const auto hi = fsv::filtered_string_view{"az", [](const auto& c) { return c != 'a'; }};

	REQUIRE(lo < hi);
	REQUIRE(lo <= hi);
	REQUIRE(not(lo > hi));
	REQUIRE(not(lo >= hi));
	REQUIRE(lo <=> hi == std::strong_ordering::less);
}

// Specification: 2.7.3 - Output Stream
// Purpose: Ensure the filtered string outputs to a stream and is filtered by
//			the predicate.
// Expected: The output stream filters the underlying data.
TEST_CASE("output stream is affected by predicate") {
	const auto view = fsv::filtered_string_view{"output!", [](const auto& c) { return c != 't'; }};

	auto stream = std::stringstream{};
	stream << view;

	REQUIRE(std::string{stream.str()} == "oupu!");
}

// Specification: 2.8.1 - Compose
// Purpose: Ensure that compose results in the logical AND expression equivalent
//			defined in the specification.
// Expected: The result of multiple predicates are applied and only those which
// 			 return true for all provided predicates are viewed in the
//			 underlying filter.
// Notes: Taken from the specification, modified for catch2.
TEST_CASE("compose functions as logical AND expression for predicates") {
	const auto best_languages = fsv::filtered_string_view{"c / c++"};
	const auto vf = std::vector<fsv::filter>{[](const char& c) { return c == 'c' || c == '+' || c == '/'; },
	                                         [](const char& c) { return c > ' '; },
	                                         [](const char&) { return true; }};

	const auto sv = fsv::compose(best_languages, vf);
	REQUIRE(std::string{sv} == "c/c++");
}

// Specification 2.8.2 - Split
// Purpose: Ensure that split conforms to the specification (similar to
//  		python3's string split).
// Expected: The delimiter should not appear in any of the split views.
// Note: Test from specification, modified for catch2.
TEST_CASE("split does not include delimiters") {
	const auto view = fsv::filtered_string_view{"0xDEADBEEF / 0xdeadbeef"};
	const auto token = fsv::filtered_string_view{" / "};
	const auto result = fsv::split(view, token);
	REQUIRE(result == std::vector<fsv::filtered_string_view>{"0xDEADBEEF", "0xdeadbeef"});
}

// Specification 2.8.2 - Split
// Purpose: Ensure that split conforms to the specification (similar to
//  		python3's string split).
// Expected: The delimiter should produce empty strings when no characters appear
//			 before or after it.
// Note: Test from specification, modified for catch2.
TEST_CASE("split produces empty strings when around lone delimiters") {
	const auto view = fsv::filtered_string_view{"xax"};
	const auto token = fsv::filtered_string_view{"x"};
	const auto result = fsv::split(view, token);

	REQUIRE(result == std::vector<fsv::filtered_string_view>{"", "a", ""});
}

// Specification 2.8.2 - Split
// Purpose: Ensure that split conforms to the specification (similar to
//  		python3's string split).
// Expected: The delimiter should produce empty strings when only delimiters
//			 are present.
// Note: Test from specification, modified for catch2.
TEST_CASE("split produces multiple empty strings around only delimiters") {
	const auto view = fsv::filtered_string_view{"xx"};
	const auto token = fsv::filtered_string_view{"x"};
	const auto result = fsv::split(view, token);

	REQUIRE(result == std::vector<fsv::filtered_string_view>{"", "", ""});
}

// Specification 2.8.2 - Split
// Purpose: Ensure that split conforms to the specification (IDENTICAL to
//  		python3's string split). We test multiple edge cases here, with
// 		    multiple delimiters on the outside and inside to ensure we conform.
// Expected: The output should match the python3 equivalent split function.
TEST_CASE("split functions as expected multiple delimiters") {
	const auto view = fsv::filtered_string_view{"a a Complicated Split Many Tokens among this stringa haha"};
	const auto token = fsv::filtered_string_view{"a"};
	const auto result = fsv::split(view, token);

	const auto expected = std::vector<fsv::filtered_string_view>{"",
	                                                             " ",
	                                                             " Complic",
	                                                             "ted Split M",
	                                                             "ny Tokens ",
	                                                             "mong this string",
	                                                             " h",
	                                                             "h",
	                                                             ""};
	REQUIRE(result == expected);
}

// Specification 2.8.3 - Substr
// Purpose: Ensure that substr conforms to the specification.
// Expected: The substring should split the view as if an offeset was provided
//			 to the original string.
// Note: Test from specification, modified for catch2.
TEST_CASE("substr splits at correct offset") {
	const auto view = fsv::filtered_string_view{"Siberian Husky"};
	REQUIRE(fsv::substr(view, 9) == "Husky");
}

// Specification 2.8.3 - Substr
// Purpose: Ensure that substr conforms to the specification.
// Expected: The substring should split the view as if an offeset was provided
//			 to the original string.
// Note: Test from specification, modified for catch2.
TEST_CASE("substr respects view predicate") {
	const auto view =
	    fsv::filtered_string_view{"Sled Dog", [](const auto& c) { return std::isupper(static_cast<unsigned char>(c)); }};
	REQUIRE(fsv::substr(view, 0, 2) == "SD");
}

// Specification 2.8.3 - Substr
// Purpose: Ensure that substr conforms to the specification.
// Expected: The substring should produce an empty string when provided with
//			 zero as a length argument.
TEST_CASE("substr produces an empty string with zero length") {
	const auto view = fsv::filtered_string_view{"length zero", [](const auto&) { return false; }};
	REQUIRE(fsv::substr(view, 0) == "");
}

// Specification: 2.9 - Iterator
// Purpose: Ensure the iterator functions correctly on an empty view.
// Expected: A std::copy of the empty view should result in an empty string.
TEST_CASE("forward iterators function on empty views") {
	const auto view = fsv::filtered_string_view{};
	auto str = std::string{};
	std::copy(std::begin(view), std::end(view), std::back_inserter(str));
	REQUIRE(str == "");
}

// Specification: 2.9 - Iterator
// Purpose: Ensure we have access to a valid iterator which conforms to the
// 			standard. Cend and Cbegin should also be available and identical to
//			the standard non-const iterator.
// Expected: A std::copy of the view should remain equal to the underlying
//			 string, given the predicate does not modify its output.
TEST_CASE("forward iterators function as expected") {
	const auto view = fsv::filtered_string_view{"iterator"};

	auto str = std::string{};
	std::copy(std::begin(view), std::end(view), std::back_inserter(str));
	REQUIRE(str == "iterator");

	str.clear();
	std::copy(std::cbegin(view), std::cend(view), std::back_inserter(str));
	REQUIRE(str == "iterator");
}

// Specification: 2.9 - Iterator
// Purpose: Ensure we have access to a valid iterator which conforms to the
// 			standard. Cend and cbegin should also be available.
// Expected: A std::copy should copy the underlying string filter.
TEST_CASE("forward iterator is affected by predicate") {
	const auto view = fsv::filtered_string_view{"iterator", [](const auto& c) { return c != 'r'; }};

	auto str = std::string{};
	std::copy(std::begin(view), std::end(view), std::back_inserter(str));
	REQUIRE(str == "iteato");

	str.clear();
	std::copy(std::cbegin(view), std::cend(view), std::back_inserter(str));
	REQUIRE(str == "iteato");
}

// Specification: 2.10 - Range
// Purpose: Ensure our iterator functions as a bidirectional range.
// Expected: A std::copy of a backwards iterator produces the view in reverse
// 			 of the begin iterators.
TEST_CASE("bidirectional iterators function as expected") {
	const auto view = fsv::filtered_string_view{"iterator"};

	auto str = std::string{};
	std::copy(std::rbegin(view), std::rend(view), std::back_inserter(str));
	REQUIRE(str == "rotareti");

	str.clear();
	std::copy(std::crbegin(view), std::crend(view), std::back_inserter(str));
	REQUIRE(str == "rotareti");
}

// Specification: 2.10 - Range
// Purpose: Ensure our iterator functions as a bidirectional range with respect
//			to the provided predicate.
// Expected: A std::copy of a backwards iterator produces the view in reverse
// 			 of the begin iterators, including the affects of the predicate.
TEST_CASE("bidirectional iterators are affected by predicate.") {
	const auto view = fsv::filtered_string_view{"iterator", [](const auto& c) { return c != 'r'; }};

	auto str = std::string{};
	std::copy(std::rbegin(view), std::rend(view), std::back_inserter(str));
	REQUIRE(str == "otaeti");

	str.clear();
	std::copy(std::crbegin(view), std::crend(view), std::back_inserter(str));
	REQUIRE(str == "otaeti");
}