final class InterpreterTests: XCTestCase {
	func testRestrictsComparisons() {
		let comparable: (Term, Term) -> Bool = { $0.extract == 0 && $1.extract == 0 }
		assert(Interpreter(equal: ==, comparable: comparable, cost: const(1)).run(a, b), ==, restricted)
	}

	func testComparisonsOfDisjointlyCategorizedTermsAreRestricted() {
		var effects = 0
		let categorize: Term -> Set<Int> = { $0.extract == 0 ? [ 0 ] : [ effects++ ] }
		assert(Interpreter(equal: ==, comparable: Interpreter.comparable(categorize), cost: const(1)).run(a, b), ==, restricted)
	}

	func testUnrestrictedComparisonsComputeReplacements() {
		assert(Interpreter(equal: ==, comparable: const(true), cost: const(1)).run(a, b), ==, unrestricted)
	}

	func testComparisonsOfUncategorizedTermsAreUnrestricted() {
		assert(Interpreter(equal: ==, comparable: Interpreter.comparable { _ in Set<String>() }, cost: const(1)).run(a, b), ==, unrestricted)
	}
}


private typealias Term = Cofree<String, Int>
private typealias Diff = Free<String, Patch<Term>>

private let a = Term(0, [ Term(1, .Leaf("a")), Term(2, .Leaf("b")), Term(3, .Leaf("c")) ])
private let b = Term(0, [ Term(1, .Leaf("c")), Term(2, .Leaf("b")), Term(3, .Leaf("a")) ])

private let restricted = Diff.Roll([
	.Pure(.Insert(Term(1, .Leaf("c")))),
	.Pure(.Delete(Term(1, .Leaf("a")))),
	Diff(Term(2, .Leaf("b"))),
	.Pure(.Insert(Term(3, .Leaf("a")))),
	.Pure(.Delete(Term(3, .Leaf("c")))),
])

private let unrestricted = Diff.Roll([
	.Pure(.Replace(Term(1, .Leaf("a")), Term(1, .Leaf("c")))),
	Diff(Term(2, .Leaf("b"))),
	.Pure(.Replace(Term(3, .Leaf("c")), Term(3, .Leaf("a")))),
])


import Assertions
@testable import Doubt
import Prelude
import XCTest