@testable import PureYAML
import Testing

@Suite("An alias node can serve as an implicit mapping key")
struct AliasAsMappingKeyTests {
    /// yaml-test-suite E76Z: an alias may stand where a mapping key is expected (`*b : value`). The
    /// scanner now emits the implicit-key indicator before an alias followed by a `:`, exactly as it
    /// does for a scalar key, and the alias resolves to the anchored node's value.
    @Test("An alias followed by a value indicator is a mapping key")
    func test_aliasIsImplicitKey() throws {
        let mapping = try requireMapping(PureYAML.parse("&a a: &b b\n*b : *a\n"))
        #expect(mapping?["a"] == .string("b"))
        #expect(mapping?["b"] == .string("a"))
    }

    /// yaml-test-suite 26DV exercises an alias key nested inside a block-mapping value, where the
    /// alias resolves to an earlier anchored scalar and becomes that nested mapping's key.
    @Test("An alias key resolves inside a nested block mapping value")
    func test_aliasKeyInNestedMapping() throws {
        let root = try requireMapping(PureYAML.parse("top1: &x scalar1\ntop3:\n  *x : scalar3\n"))
        #expect(root?["top1"] == .string("scalar1"))
        let nested = try requireMapping(#require(root?["top3"]))
        #expect(nested?["scalar1"] == .string("scalar3"))
    }

    /// A `:` written directly against an alias with no separating space is part of the alias name,
    /// not a value indicator (`:` is a valid anchor-name character), so the alias is not a key here.
    @Test("An alias with an adjacent colon keeps the colon in its name")
    func test_adjacentColonStaysInName() throws {
        let mapping = try requireMapping(PureYAML.parse("key: &a: scalar\nref: *a:\n"))
        #expect(mapping?["key"] == .string("scalar"))
        #expect(mapping?["ref"] == .string("scalar"))
    }
}