import Foundation
import Testing
@testable import Kanban

// MARK: - Fixtures

private enum Fixture {
    static let rich = """
        ---
        # board settings, hand-written
        schema: 1
        title: My Board

        project: lanework       # agent overlay
        sphere: work
        labels: [a, b, c]
        template: {order: 3}
        notes: |
          line one
            indented two
        folded: >
          wrapped
          text
        created: 2026-07-26T16:41:38Z
        modified-by: claude
        tagged: !!str 42
        "quoted key": yes
        # trailing note
        ---
        Body text.

        More body — with *markdown*.
        """

    static let minimal = """
        ---
        schema: 1
        order: 1024
        title: Thing
        ---
        Body
        """

    /// Verbatim copy of a real card written by an agent.
    static let realCard = """
        ---
        schema: 1
        title: Build the frontmatter engine with byte-perfect round-trip
        order: 3072
        created: 2026-07-26T16:41:38Z
        modified: 2026-07-26T19:06:55Z
        modified-by: claude
        source: DESIGN/01-storage-format.md
        labels: [m1-storage-read]
        ---
        Build the Frontmatter component.
        **Design constraints:**
        - index.md is YAML frontmatter between `---` delimiters, then a Markdown body.

        """

    /// A flow mapping whose continuation sits at column 0 — the shape that would fool a naive
    /// "any `key:` at column 0 starts a field" scanner.
    static let unindentedFlow = """
        ---
        flow: {a: 1,
        b: 2}
        last: x
        ---
        body
        """
}

private func parseError(_ text: String) -> FrontmatterError? {
    do {
        _ = try FrontmatterDocument.parse(text)
        return nil
    } catch {
        return error
    }
}

// MARK: - Round-trip

struct FrontmatterRoundTripTests {
    @Test(arguments: [
        Fixture.rich,
        Fixture.minimal,
        Fixture.realCard,
        Fixture.unindentedFlow,
        // body with a trailing newline
        "---\nschema: 1\n---\nbody\n",
        // body with several trailing newlines
        "---\nschema: 1\n---\nbody\n\n\n",
        // no body at all, closing delimiter unterminated
        "---\nschema: 1\n---",
        // no body, closing delimiter terminated
        "---\nschema: 1\n---\n",
        // empty frontmatter mapping
        "---\n---\nbody\n",
        // frontmatter that is only blank lines
        "---\n\n\n---\nbody\n",
        // frontmatter that is only comments
        "---\n# nothing to see\n---\nbody\n",
        // explicit empty flow mapping
        "---\n{}\n---\nbody\n",
        // top-level flow mapping
        "---\n{schema: 1, order: 5}\n---\nbody\n",
        // odd key order, blank lines between entries
        "---\nzzz: last\n\norder: 5\n\n\nschema: 1\n---\nbody\n",
        // block scalar keep/strip indicators
        "---\nkeep: |+\n  text\n\nstrip: |-\n  text\n---\nbody\n",
        // anchors and aliases
        "---\nbase: &b\n  x: 1\ncopy: *b\n---\nbody\n",
        // quoted values with escapes and embedded delimiters
        "---\ntitle: \"a \\\"quoted\\\" --- thing\"\nother: 'single ---'\n---\nbody\n",
        // a --- inside a block scalar (indented, so not a delimiter)
        "---\nnote: |\n  ---\n  still the value\n---\nbody\n",
        // delimiter line with trailing spaces
        "--- \nschema: 1\n---  \nbody\n",
        // no trailing newline on the body
        "---\nschema: 1\n---\nbody without newline",
        // CRLF throughout
        "---\r\nschema: 1\r\n---\r\nbody\r\n",
    ])
    func serializingAnUntouchedDocumentIsByteIdentical(text: String) throws {
        let document = try FrontmatterDocument.parse(text)
        #expect(document.serialized() == text)
    }

    @Test func bodyIsEverythingAfterTheClosingDelimiter() throws {
        let document = try FrontmatterDocument.parse(Fixture.rich)
        #expect(document.body == "Body text.\n\nMore body — with *markdown*.")
    }

    @Test func emptyBodyIsEmpty() throws {
        #expect(try FrontmatterDocument.parse("---\nschema: 1\n---\n").body == "")
        #expect(try FrontmatterDocument.parse("---\nschema: 1\n---").body == "")
    }

    @Test func bodyTrailingNewlinesAreNotNormalized() throws {
        let document = try FrontmatterDocument.parse("---\nschema: 1\n---\nbody\n\n\n")
        #expect(document.body == "body\n\n\n")
    }
}

// MARK: - Malformed input

struct FrontmatterMalformedTests {
    @Test func missingOpeningDelimiter() {
        #expect(parseError("schema: 1\n---\nbody\n") == .missingOpeningDelimiter)
        #expect(parseError("") == .missingOpeningDelimiter)
        #expect(parseError("\n---\nschema: 1\n---\n") == .missingOpeningDelimiter)
        #expect(parseError("----\nschema: 1\n---\n") == .missingOpeningDelimiter)
        #expect(parseError("--- yaml\nschema: 1\n---\n") == .missingOpeningDelimiter)
    }

    @Test func missingClosingDelimiter() {
        #expect(parseError("---\nschema: 1\nbody\n") == .missingClosingDelimiter)
        #expect(parseError("---\n") == .missingClosingDelimiter)
        #expect(parseError("---") == .missingClosingDelimiter)
    }

    @Test(arguments: [
        "---\nfoo: [1, 2\n---\nbody\n",
        "---\nschema: 1\n\tindented-with-tab: 2\n---\nbody\n",
        "---\nschema: 1\n  bad: indent\n---\nbody\n",
        "---\ndupe: 1\ndupe: 2\n---\nbody\n",
        "---\n\"unterminated: 1\n---\nbody\n",
        "---\nfoo: {a: 1\n---\nbody\n",
        "---\n*undefined-alias\n---\nbody\n",
    ])
    func unparseableYAML(text: String) {
        guard case .unparseableYAML = parseError(text) else {
            Issue.record("expected .unparseableYAML for \(text.debugDescription), got \(String(describing: parseError(text)))")
            return
        }
    }

    @Test func unparseableYAMLCarriesAFileRelativeLineNumber() {
        guard case let .unparseableYAML(message, line) = parseError("---\nschema: 1\n  bad: indent\n---\n") else {
            Issue.record("expected .unparseableYAML")
            return
        }
        #expect(line == 3)
        #expect(!message.isEmpty)
    }

    @Test(arguments: [
        "---\n- a\n- b\n---\nbody\n",
        "---\njust a scalar\n---\nbody\n",
        "---\n42\n---\nbody\n",
        "---\n[1, 2]\n---\nbody\n",
    ])
    func frontmatterNotAMapping(text: String) {
        #expect(parseError(text) == .frontmatterNotAMapping)
    }

    @Test(arguments: [
        "---\n---\nbody\n",
        "---\n\n---\nbody\n",
        "---\n# just a comment\n---\nbody\n",
        "---\n{}\n---\nbody\n",
        "---\nnull\n---\nbody\n",
        "---\n~\n---\nbody\n",
    ])
    func emptyFrontmatterIsAnEmptyMapping(text: String) throws {
        let document = try FrontmatterDocument.parse(text)
        #expect(document.keys.isEmpty)
        #expect(document.serialized() == text)
    }

    @Test func wellFormedButUnusualYAMLIsAccepted() throws {
        for text in [Fixture.rich, Fixture.unindentedFlow, "---\nbase: &b\n  x: 1\ncopy: *b\n---\n"] {
            #expect(parseError(text) == nil)
        }
    }
}

// MARK: - Generic access

struct FrontmatterAccessTests {
    @Test func keysAreInDocumentOrder() throws {
        let document = try FrontmatterDocument.parse(Fixture.rich)
        #expect(document.keys == [
            "schema", "title", "project", "sphere", "labels", "template",
            "notes", "folded", "created", "modified-by", "tagged", "quoted key",
        ])
    }

    @Test func realCardReadsAsExpected() throws {
        let document = try FrontmatterDocument.parse(Fixture.realCard)
        #expect(document.schema == .valid(1))
        #expect(document.order == .valid(3072))
        #expect(document.title == .valid("Build the frontmatter engine with byte-perfect round-trip"))
        #expect(document.modifiedBy == .valid("claude"))
        #expect(document.created.value != nil)
        #expect(document.unknownFields.map(\.key) == ["source", "labels"])
        #expect(document.body.hasPrefix("Build the Frontmatter component.\n"))
    }

    @Test func unknownKeysExcludeSchemaOwnedOnes() throws {
        let document = try FrontmatterDocument.parse(Fixture.rich)
        #expect(document.unknownFields.map(\.key) == [
            "project", "sphere", "labels", "template", "notes", "folded", "tagged", "quoted key",
        ])
    }

    @Test func modifiedByIsExposedDistinctlyAndIsNotAnUnknownKey() throws {
        let document = try FrontmatterDocument.parse(Fixture.rich)
        #expect(document.modifiedBy == .valid("claude"))
        #expect(!document.unknownFields.contains { $0.key == "modified-by" })
        #expect(document.contains("modified-by"))
    }

    @Test func reservedKeysAreOrdinaryUnknownKeys() throws {
        let text = """
            ---
            schema: 1
            labels: [bug, ui]
            assignees: [ann]
            due: 2026-08-01
            remote: {kind: gitea}
            remote-state: synced
            template: {order: 2}
            ---
            body

            """
        let document = try FrontmatterDocument.parse(text)
        #expect(document.unknownFields.map(\.key)
            == ["labels", "assignees", "due", "remote", "remote-state", "template"])
        #expect(document.serialized() == text)
    }

    @Test func parsedValuesAreAvailableForUnknownKeys() throws {
        let document = try FrontmatterDocument.parse(Fixture.rich)
        #expect(document.value(for: "labels") == .sequence([.string("a"), .string("b"), .string("c")]))
        #expect(document.value(for: "template")
            == .mapping([YAMLValue.Pair(key: .string("order"), value: .int(3))]))
        #expect(document.value(for: "quoted key") == .bool(true))
        #expect(document.value(for: "tagged") == .string("42"))
        #expect(document.value(for: "nope") == nil)
    }

    @Test func rawValuePreservesBlockScalarsVerbatim() throws {
        let document = try FrontmatterDocument.parse(Fixture.rich)
        #expect(document.rawValue(for: "notes") == "|\n  line one\n    indented two")
        #expect(document.rawValue(for: "labels") == "[a, b, c]")
        #expect(document.rawValue(for: "schema") == "1")
    }
}

// MARK: - Strict fields

struct FrontmatterStrictFieldTests {
    private func document(_ frontmatter: String) throws -> FrontmatterDocument {
        try FrontmatterDocument.parse("---\n\(frontmatter)\n---\nbody\n")
    }

    @Test func schemaValidMissingMalformed() throws {
        #expect(try document("schema: 1").schema == .valid(1))
        #expect(try document("title: x").schema == .missing)
        #expect(try document("schema:").schema == .missing)
        #expect(try document("schema: banana").schema == .malformed(raw: "banana"))
        #expect(try document("schema: 1.5").schema == .malformed(raw: "1.5"))
        #expect(try document("schema: [1]").schema == .malformed(raw: "[1]"))
    }

    @Test func orderValidMissingMalformed() throws {
        #expect(try document("order: 1024").order == .valid(1024))
        #expect(try document("order: 1536.5").order == .valid(1536.5))
        #expect(try document("order: -1024").order == .valid(-1024))
        #expect(try document("schema: 1").order == .missing)
        #expect(try document("order:").order == .missing)
    }

    @Test func nonNumericOrderIsMalformedNotNil() throws {
        let malformed = try document("order: banana").order
        #expect(malformed == .malformed(raw: "banana"))
        #expect(malformed.value == nil)
        #expect(malformed.isMalformed)
        #expect(!malformed.isMissing)
        #expect(malformed.rawText == "banana")

        #expect(try document("order: \"1024\"").order == .malformed(raw: "\"1024\""))
        #expect(try document("order: [1]").order == .malformed(raw: "[1]"))
    }
}

// MARK: - Lenient fields

struct FrontmatterLenientFieldTests {
    private func document(_ frontmatter: String) throws -> FrontmatterDocument {
        try FrontmatterDocument.parse("---\n\(frontmatter)\n---\nbody\n")
    }

    @Test func wellFormedLenientValues() throws {
        #expect(try document("title: My Board").title == .valid("My Board"))
        #expect(try document("background: \"#ff8800\"").background == .valid("#ff8800"))
        #expect(try document("background: slate").background == .valid("slate"))
        #expect(try document("icon: tray.full").icon == .valid("tray.full"))
        #expect(try document("iconColor: teal").iconColor == .valid("teal"))
        #expect(try document("width: 3").width == .valid(3))
        #expect(try document("width: 1").width == .valid(1))
    }

    @Test func malformedLenientValuesArePreservedVerbatimAndDoNotThrow() throws {
        #expect(try document("background: [red, blue]").background == .malformed(raw: "[red, blue]"))
        #expect(try document("background: 42").background == .malformed(raw: "42"))
        #expect(try document("icon: {a: 1}").icon == .malformed(raw: "{a: 1}"))
        #expect(try document("iconColor: true").iconColor == .malformed(raw: "true"))
        #expect(try document("title: [a, b]").title == .malformed(raw: "[a, b]"))
    }

    @Test func widthIsLenientForAnythingButAnIntegerAtLeastOne() throws {
        #expect(try document("width: 0").width == .malformed(raw: "0"))
        #expect(try document("width: -3").width == .malformed(raw: "-3"))
        #expect(try document("width: 1.5").width == .malformed(raw: "1.5"))
        #expect(try document("width: wide").width == .malformed(raw: "wide"))
        #expect(try document("schema: 1").width == .missing)
    }

    @Test func malformedLenientValuesStillRoundTrip() throws {
        let text = "---\nschema: 1\nbackground: [red, blue]\nwidth: 0\nicon: {a: 1}\n---\nbody\n"
        let document = try FrontmatterDocument.parse(text)
        #expect(document.serialized() == text)
        #expect(document.background.isMalformed)
        #expect(document.width.isMalformed)
        #expect(document.icon.isMalformed)
    }

    @Test func timestampsReadPlainAndQuoted() throws {
        let expected = Date(timeIntervalSince1970: 1_785_084_098)  // 2026-07-26T16:41:38Z
        #expect(try document("created: 2026-07-26T16:41:38Z").created == .valid(expected))
        #expect(try document("modified: \"2026-07-26T16:41:38Z\"").modified == .valid(expected))
        #expect(try document("deleted: 2026-07-26T16:41:38Z").deleted == .valid(expected))
        #expect(try document("schema: 1").deleted == .missing)
        #expect(try document("created: never").created == .malformed(raw: "never"))
    }
}

// MARK: - Surgical edits

struct FrontmatterEditTests {
    @Test func settingOneKeyLeavesEveryOtherByteIdentical() throws {
        var document = try FrontmatterDocument.parse(Fixture.rich)
        document.set("title", to: .string("Renamed"))
        let output = document.serialized()

        let expected = Fixture.rich.replacingOccurrences(of: "title: My Board", with: "title: Renamed")
        #expect(output == expected)

        // Prefix and suffix around the edited span are untouched.
        let marker = "title: "
        let originalPrefix = Fixture.rich.prefix(while: { _ in true }).components(separatedBy: marker)[0]
        #expect(output.hasPrefix(originalPrefix))
        #expect(output.hasSuffix("\nMore body — with *markdown*."))
    }

    @Test func settingAKeyPreservesItsTrailingCommentsAndBlankLines() throws {
        let text = "---\nschema: 1\nproject: lanework       # agent overlay\n\n# a note\norder: 5\n---\nbody\n"
        var document = try FrontmatterDocument.parse(text)
        document.set("project", to: .string("kanban"))
        #expect(document.serialized()
            == "---\nschema: 1\nproject: kanban\n\n# a note\norder: 5\n---\nbody\n")
    }

    @Test func appendingANewKeyGoesBeforeTheClosingDelimiter() throws {
        var document = try FrontmatterDocument.parse(Fixture.minimal)
        document.set("modified", to: .date(Date(timeIntervalSince1970: 1_785_084_098)))
        #expect(document.serialized() == """
            ---
            schema: 1
            order: 1024
            title: Thing
            modified: 2026-07-26T16:41:38Z
            ---
            Body
            """)
        #expect(document.keys == ["schema", "order", "title", "modified"])
    }

    @Test func appendingToEmptyFrontmatter() throws {
        var document = try FrontmatterDocument.parse("---\n---\nbody\n")
        document.set("schema", to: .int(1))
        #expect(document.serialized() == "---\nschema: 1\n---\nbody\n")
        #expect(document.schema == .valid(1))
    }

    @Test func removingAKeyDeletesOnlyItsLines() throws {
        var document = try FrontmatterDocument.parse(Fixture.minimal)
        document.remove("order")
        #expect(document.serialized() == "---\nschema: 1\ntitle: Thing\n---\nBody")
        #expect(document.order == .missing)
        #expect(document.keys == ["schema", "title"])
    }

    @Test func removingAKeyKeepsTrailingComments() throws {
        var document = try FrontmatterDocument.parse("---\na: 1\n# note about b\nb: 2\n---\nbody\n")
        document.remove("a")
        #expect(document.serialized() == "---\n# note about b\nb: 2\n---\nbody\n")
    }

    @Test func removingAnAbsentKeyIsANoOp() throws {
        var document = try FrontmatterDocument.parse(Fixture.minimal)
        document.remove("nope")
        #expect(document.serialized() == Fixture.minimal)
    }

    @Test func editingAKeyWhoseValueWasABlockScalar() throws {
        var document = try FrontmatterDocument.parse(Fixture.rich)
        document.set("notes", to: .string("flattened"))
        #expect(document.serialized().contains("notes: flattened\nfolded: >\n"))
        #expect(!document.serialized().contains("line one"))
        #expect(document.value(for: "notes") == .string("flattened"))
        // Everything after the edited span is untouched.
        #expect(document.serialized().hasSuffix("More body — with *markdown*."))
    }

    @Test func editingAKeyAfterAnUnindentedFlowContinuation() throws {
        var document = try FrontmatterDocument.parse(Fixture.unindentedFlow)
        document.set("last", to: .string("y"))
        #expect(document.serialized() == "---\nflow: {a: 1,\nb: 2}\nlast: y\n---\nbody")
    }

    @Test func editingAQuotedKeyKeepsItsOriginalSpelling() throws {
        var document = try FrontmatterDocument.parse("---\n\"quoted key\": one\n---\nbody\n")
        document.set("quoted key", to: .string("two"))
        #expect(document.serialized() == "---\n\"quoted key\": two\n---\nbody\n")
    }

    @Test func buildingADocumentFromScratch() throws {
        var document = FrontmatterDocument(body: "The card body.\n")
        document.set("schema", to: .int(1))
        document.set("order", to: .double(1024))
        document.set("title", to: .string("New card"))
        let text = document.serialized()
        #expect(text == "---\nschema: 1\norder: 1024\ntitle: New card\n---\nThe card body.\n")
        #expect(try FrontmatterDocument.parse(text).serialized() == text)
    }

    @Test func settingTheBodyReplacesOnlyTheBody() throws {
        var document = try FrontmatterDocument.parse(Fixture.rich)
        document.body = "Brand new body.\n"
        let output = document.serialized()
        #expect(output.hasSuffix("---\nBrand new body.\n"))
        #expect(output.hasPrefix("---\n# board settings, hand-written\nschema: 1\n"))
        #expect(!output.contains("More body"))
    }

    @Test func editsSurviveReparsing() throws {
        var document = try FrontmatterDocument.parse(Fixture.rich)
        document.set("order", to: .double(2048))
        document.remove("modified-by")
        document.set("title", to: .string("Renamed"))

        let reparsed = try FrontmatterDocument.parse(document.serialized())
        #expect(reparsed.order == .valid(2048))
        #expect(reparsed.modifiedBy == .missing)
        #expect(reparsed.title == .valid("Renamed"))
        #expect(reparsed.unknownFields.map(\.key)
            == ["project", "sphere", "labels", "template", "notes", "folded", "tagged", "quoted key"])
        #expect(reparsed.serialized() == document.serialized())
    }
}

// MARK: - Scalar emission

struct FrontmatterEmissionTests {
    private func emittedTitle(_ value: FrontmatterValue) throws -> String {
        var document = try FrontmatterDocument.parse("---\n---\n")
        document.set("title", to: value)
        return String(document.serialized().dropFirst("---\ntitle: ".count).dropLast("\n---\n".count))
    }

    @Test func numbersAndTimestampsAreEmittedPlain() throws {
        #expect(try emittedTitle(.int(42)) == "42")
        #expect(try emittedTitle(.double(1024)) == "1024")
        #expect(try emittedTitle(.double(1536.5)) == "1536.5")
        #expect(try emittedTitle(.bool(true)) == "true")
        #expect(try emittedTitle(.date(Date(timeIntervalSince1970: 1_785_084_098))) == "2026-07-26T16:41:38Z")
    }

    @Test func ordinaryStringsAreEmittedPlain() throws {
        #expect(try emittedTitle(.string("My Board")) == "My Board")
        #expect(try emittedTitle(.string("Fix login — round 2")) == "Fix login — round 2")
        #expect(try emittedTitle(.string("a/b?c")) == "a/b?c")
    }

    @Test(arguments: [
        "",
        " padded ",
        "true",
        "yes",
        "null",
        "~",
        "42",
        "1.5",
        "2026-07-26T16:41:38Z",
        "has: a colon",
        "trailing colon:",
        "hash # comment",
        "#ff8800",
        "- leading dash",
        "[bracketed]",
        "{braced}",
        "line\nbreak",
        "tab\there",
        "quote\"inside",
        "back\\slash",
        "*anchor",
        "&anchor",
        "!tagged",
        "%directive",
        "@at",
        "|pipe",
        ">gt",
        "'single'",
    ])
    func stringsNeedingQuotingSurviveAReparse(value: String) throws {
        var document = try FrontmatterDocument.parse("---\n---\n")
        document.set("title", to: .string(value))
        let reparsed = try FrontmatterDocument.parse(document.serialized())
        #expect(reparsed.title == .valid(value))
    }

    @Test func quotingIsUsedOnlyWhenNeeded() throws {
        #expect(try emittedTitle(.string("true")) == "\"true\"")
        #expect(try emittedTitle(.string("#ff8800")) == "\"#ff8800\"")
        #expect(try emittedTitle(.string("")) == "\"\"")
        #expect(try emittedTitle(.string("a\nb")) == "\"a\\nb\"")
        // An interior quote is legal in a plain scalar; a leading one is not.
        #expect(try emittedTitle(.string("say \"hi\"")) == "say \"hi\"")
        #expect(try emittedTitle(.string("\"quoted\"")) == "\"\\\"quoted\\\"\"")
        #expect(try emittedTitle(.string("back\\slash")) == "back\\slash")
    }

    @Test func rawValuesAreWrittenVerbatim() throws {
        var document = try FrontmatterDocument.parse("---\nschema: 1\n---\nbody\n")
        document.set("template", to: .raw("{order: 7}"))
        #expect(document.serialized() == "---\nschema: 1\ntemplate: {order: 7}\n---\nbody\n")
        #expect(document.value(for: "template")
            == .mapping([YAMLValue.Pair(key: .string("order"), value: .int(7))]))
    }
}