package docsite

import (
	"os"
	"path/filepath"
	"runtime"
	"slices"
	"strings"
	"testing"
)

const genericGo = `package gen

// Map applies f to every element.
func Map[T, U any](in []T, f func(T) U) []U {
	out := make([]U, 0, len(in))
	for _, v := range in {
		out = append(out, f(v))
	}
	return out
}

// Box holds one value.
type Box[T any] struct{ v T }

// Get returns the value.
func (b *Box[T]) Get() T { return b.v }

// Pair holds a key and a value.
type Pair[K comparable, V any] struct {
	K K
	V V
}

// Key returns the key.
func (p Pair[K, V]) Key() K { return p.K }

// Paren has a parenthesised receiver.
func (b (*Box[T])) Paren() {}

var (
	// Limit is documented in the group.
	Limit = 10
	Other = 2
)

// Single is an ungrouped var.
var Single = 1

type (
	// ID is a grouped type.
	ID int
)
`

const genericTestGo = `package gen

import (
	"fmt"
	"testing"
)

func TestMap(t *testing.T) {
	// docs:start map
	got := Map([]int{1, 2}, func(v int) string {
		return fmt.Sprint(v)
	})
	// docs:end map
	_ = viaVar
	if len(got) != 2 || (fixture{name: "x"}).name == "" {
		t.Fatal(got)
	}
	// docs:start map
	duplicate := 1
	// docs:end map
	_ = duplicate
}

// fixture is referenced by a test, so it counts as run.
type fixture struct{ name string }

// indirect is only reached through a package-level var: the run check is
// conservative and does not follow var initialisers.
type indirect struct{}

var viaVar = indirect{}

func ExampleBox_Get() {
	b := &Box[string]{v: "boxed"}
	if b != nil {
		fmt.Println(b.Get())
	}
	// Output: boxed
}

func ExamplePair_Key() {
	fmt.Println(Pair[string, int]{K: "k"}.Key())
	// Output:
	// k
}

func ExampleSingle() {
	_ = Single
	// Output:
}
`

func genericTree(t *testing.T) string {
	t.Helper()
	return writeTree(t, map[string]string{
		"go.mod":              "module example.com/gen\n\ngo 1.27\n",
		"gen/gen.go":          genericGo,
		"gen/gen_test.go":     genericTestGo,
		"config/app.yaml":     "a:\n  # docs:start keys\n  b: 1\n\n  c: 2\n  # docs:end keys\n",
		"config/tabs.go.txt":  "x",
		"docs/site.yaml":      snippetSite,
		"docs/index.md":       page("Acme docs", "index", 0, "Hello.\n"),
		"docs/setup/start.md": page("Start", "setup", 10, "Text.\n"),
	})
}

func TestSnippetGenericsAndGroups(t *testing.T) {
	root := genericTree(t)
	for _, tc := range []struct {
		ref  Ref
		want string
	}{
		{Ref{"gen/gen.go", "Map"}, "// Map applies f to every element.\nfunc Map[T, U any](in []T, f func(T) U) []U {\n\tout := make([]U, 0, len(in))\n\tfor _, v := range in {\n\t\tout = append(out, f(v))\n\t}\n\treturn out\n}"},
		{Ref{"gen/gen.go", "Box"}, "// Box holds one value.\ntype Box[T any] struct{ v T }"},
		{Ref{"gen/gen.go", "Box.Get"}, "// Get returns the value.\nfunc (b *Box[T]) Get() T { return b.v }"},
		{Ref{"gen/gen.go", "Pair.Key"}, "// Key returns the key.\nfunc (p Pair[K, V]) Key() K { return p.K }"},
		{Ref{"gen/gen.go", "Box.Paren"}, "// Paren has a parenthesised receiver.\nfunc (b (*Box[T])) Paren() {}"},
		{Ref{"gen/gen.go", "Limit"}, "// Limit is documented in the group.\n\tLimit = 10"},
		{Ref{"gen/gen.go", "Other"}, "Other = 2"},
		{Ref{"gen/gen.go", "Single"}, "// Single is an ungrouped var.\nvar Single = 1"},
		{Ref{"gen/gen.go", "ID"}, "// ID is a grouped type.\n\tID int"},
		{Ref{"gen/gen_test.go", "ExampleBox_Get"}, "b := &Box[string]{v: \"boxed\"}\nif b != nil {\n\tfmt.Println(b.Get())\n}\n// Output: boxed"},
		{Ref{"gen/gen_test.go", "ExamplePair_Key"}, "fmt.Println(Pair[string, int]{K: \"k\"}.Key())\n// Output:\n// k"},
		{Ref{"gen/gen_test.go", "ExampleSingle"}, "_ = Single\n// Output:"},
		{Ref{"gen/gen_test.go", "fixture"}, "// fixture is referenced by a test, so it counts as run.\ntype fixture struct{ name string }"},
		{Ref{"gen/gen_test.go", "viaVar"}, "var viaVar = indirect{}"},
		// The first of two same-named regions wins.
		{Ref{"gen/gen_test.go", "map"}, "got := Map([]int{1, 2}, func(v int) string {\n\treturn fmt.Sprint(v)\n})"},
		// A YAML region keeps its inner blank line and is dedented.
		{Ref{"config/app.yaml", "keys"}, "b: 1\n\nc: 2"},
	} {
		got, err := Extract(root, tc.ref)
		if err != nil {
			t.Errorf("Extract(%s): %v", tc.ref, err)
			continue
		}
		if got != tc.want {
			t.Errorf("Extract(%s) =\n%q\nwant\n%q", tc.ref, got, tc.want)
		}
	}
	if _, err := Extract(root, Ref{"gen/gen_test.go", "indirect"}); err == nil || err.Error() != notRunMessage {
		t.Errorf("Extract(indirect) = %v, want the not-run refusal", err)
	}
	// A fragment on a non-Go file that is not a region is not found.
	if _, err := Extract(root, Ref{"config/app.yaml", "Map"}); err != errSnippetNotFound {
		t.Errorf("YAML ident err = %v", err)
	}
	// A missing root is an error, not a problem.
	if _, err := Extract(filepath.Join(root, "missing"), Ref{Path: "gen/gen.go"}); err == nil || err == errSnippetNotFound {
		t.Errorf("Extract with a missing root = %v", err)
	}
}

func TestDedent(t *testing.T) {
	for _, tc := range []struct {
		in, want []string
	}{
		{[]string{"", "\t\ta", "\t\t\tb", "", "\t\tc", "  "}, []string{"a", "\tb", "", "c"}},
		{[]string{"    x", "  y"}, []string{"  x", "y"}},
		{[]string{"\t x", "\t\ty"}, []string{" x", "\ty"}},
		{[]string{"  ", ""}, []string{}},
		{nil, []string{}},
	} {
		if got := dedent(tc.in); !slices.Equal(got, tc.want) {
			t.Errorf("dedent(%q) = %q, want %q", tc.in, got, tc.want)
		}
	}
}

func TestSnippetRefPathRules(t *testing.T) {
	for p, want := range map[string]string{
		"":             "src= has no path",
		"/abs.go":      "must be relative",
		`\abs.go`:      "must be relative",
		"C:/x.go":      "must be relative",
		"c:x.go":       "must be relative",
		`a\b.go`:       "must use forward slashes",
		"a/../b.go":    "must not leave the repository root",
		"a/.git/x":     "dotfile or .env file",
		"a/prod.env":   "dotfile or .env file",
		"./a.go":       "dotfile or .env file",
		"a//b.go":      "must be clean",
		"a/b/":         "must be clean",
		"a/b.go":       "",
		"docs/x.md":    "",
		"environment":  "",
		"a.environ.go": "",
	} {
		err := checkRefPath(p)
		if (want == "") != (err == nil) || (err != nil && !strings.Contains(err.Error(), want)) {
			t.Errorf("checkRefPath(%q) = %v, want %q", p, err, want)
		}
	}
	for info, want := range map[string]Ref{
		"go src=a.go#X":       {"a.go", "X"},
		"yaml   src=b.yaml":   {"b.yaml", ""},
		"go title=x src=c.go": {"c.go", ""},
		"go src=d.go#A#B":     {"d.go", "A#B"},
	} {
		if got, ok := ParseSrc(info); !ok || got != want {
			t.Errorf("ParseSrc(%q) = %+v, %v", info, got, ok)
		}
	}
	if (Ref{Path: "a.go"}).String() != "a.go" || (Ref{"a.go", "X"}).String() != "a.go#X" {
		t.Error("Ref.String")
	}
}

func TestSnippetSymlinkInsideRoot(t *testing.T) {
	root := genericTree(t)
	if err := os.Symlink(filepath.Join(root, "config", "app.yaml"), filepath.Join(root, "config", "alias.yaml")); err != nil {
		t.Fatal(err)
	}
	got, err := Extract(root, Ref{"config/alias.yaml", "keys"})
	if err != nil || got != "b: 1\n\nc: 2" {
		t.Fatalf("Extract through an in-root symlink = %q, %v", got, err)
	}
}

func TestSnippetTrailingNewlines(t *testing.T) {
	// A fence body with or without trailing blank lines matches a source
	// ending in newlines; any other difference is drift.
	body := "```yaml src=config/app.yaml#keys\nb: 1\n\nc: 2\n\n\n```\n\n" +
		"```text src=config/whole.txt\nline\n```\n\n" +
		"  ```text src=config/whole.txt\n  line\n  ```\n"
	root := snippetTree(t, map[string]string{
		"config/app.yaml":     "a:\n  # docs:start keys\n  b: 1\n\n  c: 2\n  # docs:end keys\n",
		"config/whole.txt":    "line\n\n\n",
		"docs/setup/start.md": page("Start", "setup", 10, body),
	})
	if problems, err := Check(Options{Root: root, Commands: fixtureCommands}); err != nil || len(problems) > 0 {
		t.Fatalf("Check: %v %q", err, problemLines(problems))
	}
}

func TestSyncPreservesAndReports(t *testing.T) {
	doc := page("Start", "setup", 10, "Before.\n\n```go src=pkg/lib.go#Greeting\nold one\n```\n\nMiddle `x`.\n\n"+
		"```go src=pkg/lib_test.go#ExampleGreeting\nold two\n```\n\n```go src=pkg/lib.go#Greeting\n// Greeting returns a greeting.\n"+
		"func Greeting(name string) string {\n\treturn \"Hello, \" + name\n}\n```\n\nAfter.")
	root := snippetTree(t, map[string]string{"docs/setup/start.md": doc})
	path := filepath.Join(root, "docs/setup/start.md")
	if err := os.Chmod(path, 0o600); err != nil {
		t.Fatal(err)
	}
	res, problems, err := Sync(Options{Root: root})
	if err != nil || len(problems) > 0 || res != (SyncResult{Snippets: 2, Files: 1}) {
		t.Fatalf("Sync = %+v %q %v", res, problemLines(problems), err)
	}
	got, err := os.ReadFile(path)
	if err != nil {
		t.Fatal(err)
	}
	want := strings.Replace(strings.Replace(doc, "old one", "// Greeting returns a greeting.\nfunc Greeting(name string) string {\n\treturn \"Hello, \" + name\n}", 1),
		"old two", "fmt.Println(Greeting(\"blog\"))\n// Output: Hello, blog", 1)
	if string(got) != want {
		t.Fatalf("synced =\n%s\nwant\n%s", got, want)
	}
	if st, err := os.Stat(path); err != nil || st.Mode().Perm() != 0o600 {
		t.Fatalf("mode after Sync = %v, %v; want 0600", st.Mode().Perm(), err)
	}
	if res, _, err := Sync(Options{Root: root}); err != nil || res != (SyncResult{}) {
		t.Fatalf("second Sync = %+v, %v", res, err)
	}

	// One broken reference anywhere means Sync writes nothing at all.
	other := page("Other", "setup", 20, "```go src=pkg/lib.go#Greeting\nstale\n```\n")
	broken := page("Broken", "setup", 30, "```go src=pkg/lib.go#Missing\n```\n")
	root = snippetTree(t, map[string]string{"docs/setup/other.md": other, "docs/setup/broken.md": broken})
	res, problems, err = Sync(Options{Root: root})
	if err != nil || res != (SyncResult{}) {
		t.Fatalf("Sync with a broken ref = %+v, %v", res, err)
	}
	assertProblems(t, problemLines(problems), []string{"docs/setup/broken.md:9: snippet: pkg/lib.go#Missing not found"})
	if got, _ := os.ReadFile(filepath.Join(root, "docs/setup/other.md")); string(got) != other {
		t.Fatal("Sync wrote a file although another reference was broken")
	}
	if _, _, err := Sync(Options{Root: root, Src: filepath.Join(root, "missing")}); err == nil {
		t.Fatal("Sync on a missing source directory returned no error")
	}
}

func TestSnippetTestGraph(t *testing.T) {
	root := writeTree(t, map[string]string{
		"p/p.go":      "package p\n",
		"p/a_test.go": "package p\n\nimport \"testing\"\n\nfunc TestA(t *testing.T) { helperOne() }\n\nfunc helperOne() { helperTwo() }\n",
		"p/b_test.go": "package p\n\nfunc helperTwo() {\n\t// docs:start deep\n\t_ = 1\n\t// docs:end deep\n}\n\nfunc (s *suite) run() {}\n\ntype suite struct{}\n\nfunc lonely() {}\n",
	})
	for _, tc := range []struct {
		ref  Ref
		want string
	}{
		{Ref{"p/b_test.go", "deep"}, ""},
		{Ref{"p/b_test.go", "helperTwo"}, ""},
		{Ref{"p/b_test.go", "lonely"}, notRunMessage},
		{Ref{"p/b_test.go", "suite.run"}, notRunMessage},
		{Ref{"p/b_test.go", "suite"}, notRunMessage},
	} {
		_, err := Extract(root, tc.ref)
		if (tc.want == "") != (err == nil) || (err != nil && err.Error() != tc.want) {
			t.Errorf("Extract(%s) = %v, want %q", tc.ref, err, tc.want)
		}
	}
	// A test file that does not parse is reported, not skipped.
	writeFile(t, root, "p/c_test.go", "package p\n\nfunc {\n")
	if _, err := Extract(root, Ref{"p/b_test.go", "deep"}); err == nil || !strings.Contains(err.Error(), "cannot parse c_test.go") {
		t.Errorf("Extract with an unparsable sibling test = %v", err)
	}
}

func TestSnippetRootsAndBuild(t *testing.T) {
	other := "windows"
	if runtime.GOOS == "windows" {
		other = "linux"
	}
	root := writeTree(t, map[string]string{
		"p/p.go": "package p\n",
		"p/p_test.go": `package p

import "testing"

func Test(t *testing.T) { fromTest() }
func Test_x(t *testing.T) { fromTestX() }
func TestMain(m *testing.M) { fromMain() }
func Testable() { fromTestable() }

func fromTest() {}
func fromTestX() {}
func fromMain() {}
func fromTestable() {}
func onlyFromIgnored() {}

func ExampleOut() {
	fromOut()
	// Output: out
}

func ExampleEmpty() {
	fromEmpty()
	// Output:
}

func ExampleNone() {
	fromNone()
}

func fromOut() {}
func fromEmpty() {}
func fromNone() {}
`,
		"p/ignored_test.go":       "//go:build ignore\n\npackage p\n\nimport \"testing\"\n\nfunc TestIgnored(t *testing.T) { onlyFromIgnored() }\n",
		"p/broken.go":             "//go:build ignore\n\npackage p\n\nfunc Broken() {}\n",
		"p/broken_test.go":        "//go:build ignore\n\npackage p\n\nfunc IgnoredTestTarget() {}\n",
		"p/only_" + other + ".go": "package p\n\nfunc OnlyOS() {}\n",
		"p/testdata/skip.go":      "package p\n\nfunc Skip() {}\n",
		"p/_old/old.go":           "package p\n\nfunc Old() {}\n",
		"p/testdata/app.yaml":     "# docs:start db\nhost: localhost\n# docs:end db\n",
	})
	g, err := loadTestGraph(filepath.Join(root, "p"))
	if err != nil {
		t.Fatal(err)
	}
	for _, name := range []string{"Test", "Test_x", "TestMain", "ExampleOut", "ExampleEmpty", "fromTest", "fromTestX", "fromMain", "fromOut", "fromEmpty"} {
		if !g.reachable[name] {
			t.Errorf("%s is not a root or reachable from one", name)
		}
	}
	for _, name := range []string{"Testable", "ExampleNone", "fromTestable", "fromNone", "onlyFromIgnored", "TestIgnored"} {
		if g.reachable[name] {
			t.Errorf("%s is reachable, want it not run", name)
		}
	}
	mustExtract := func(ref Ref, wantErr string) {
		t.Helper()
		_, err := Extract(root, ref)
		if wantErr == "" {
			if err != nil {
				t.Errorf("Extract(%s) = %v, want nil", ref, err)
			}
			return
		}
		if err == nil || !strings.Contains(err.Error(), wantErr) {
			t.Errorf("Extract(%s) = %v, want %q", ref, err, wantErr)
		}
	}
	skipped := "file is in a directory go test ./... skips"
	excluded := "file is excluded from the default build"
	mustExtract(Ref{"p/p_test.go", "fromOut"}, "")
	mustExtract(Ref{"p/p_test.go", "fromEmpty"}, "")
	mustExtract(Ref{"p/p_test.go", "fromNone"}, notRunMessage)
	mustExtract(Ref{"p/p_test.go", "fromTestable"}, notRunMessage)
	mustExtract(Ref{"p/p_test.go", "onlyFromIgnored"}, notRunMessage)
	mustExtract(Ref{"p/broken.go", "Broken"}, excluded)
	mustExtract(Ref{"p/broken_test.go", "IgnoredTestTarget"}, excluded)
	mustExtract(Ref{"p/only_" + other + ".go", "OnlyOS"}, excluded)
	mustExtract(Ref{"p/testdata/skip.go", "Skip"}, skipped)
	mustExtract(Ref{"p/_old/old.go", "Old"}, skipped)
	got, err := Extract(root, Ref{"p/testdata/app.yaml", "db"})
	if err != nil || got != "host: localhost" {
		t.Fatalf("Extract yaml = %q, %v", got, err)
	}
}

func TestSyncParsedFences(t *testing.T) {
	callout := "> [!NOTE]\n> Keep this callout text.\n"
	doc := page("Start", "setup", 10, "Intro.\n\n```go src=pkg/lib.go#Greeting\nfunc stale() {}\n```\n\n"+callout+"\nOutro.\n")
	root := snippetTree(t, map[string]string{"docs/setup/start.md": doc})
	path := filepath.Join(root, "docs/setup/start.md")
	res, problems, err := Sync(Options{Root: root})
	if err != nil || len(problems) > 0 {
		t.Fatalf("Sync: %v %v", err, problems)
	}
	if res.Files != 1 || res.Snippets != 1 {
		t.Fatalf("Sync = %+v, want 1 snippet in 1 file", res)
	}
	got, err := os.ReadFile(path)
	if err != nil {
		t.Fatal(err)
	}
	wantDoc := strings.Replace(doc, "func stale() {}\n",
		"// Greeting returns a greeting.\nfunc Greeting(name string) string {\n\treturn \"Hello, \" + name\n}\n", 1)
	if string(got) != wantDoc {
		t.Fatalf("synced file =\n%s\nwant\n%s", got, wantDoc)
	}
	if !strings.HasPrefix(string(got), "---\ntitle: Start\n") || !strings.Contains(string(got), callout) {
		t.Fatal("frontmatter or callout text changed")
	}

	nested := page("Start", "setup", 10, "Intro.\n\n> [!NOTE]\n> ```go src=pkg/lib.go#Greeting\n> func stale() {}\n> ```\n\nOutro.\n")
	root = snippetTree(t, map[string]string{"docs/setup/start.md": nested})
	before := map[string]string{}
	err = filepath.WalkDir(root, func(p string, d os.DirEntry, err error) error {
		if err != nil || d.IsDir() {
			return err
		}
		b, err := os.ReadFile(p)
		if err != nil {
			return err
		}
		before[p] = string(b)
		return nil
	})
	if err != nil {
		t.Fatal(err)
	}
	res, problems, err = Sync(Options{Root: root})
	if err != nil || res != (SyncResult{}) || len(problems) != 1 || !strings.Contains(problems[0].Message, nestedSrcMessage) {
		t.Fatalf("nested Sync = %+v %q %v", res, problemLines(problems), err)
	}
	err = filepath.WalkDir(root, func(p string, d os.DirEntry, err error) error {
		if err != nil || d.IsDir() {
			return err
		}
		b, err := os.ReadFile(p)
		if err != nil {
			return err
		}
		if string(b) != before[p] {
			t.Errorf("Sync changed %s", p)
		}
		return nil
	})
	if err != nil {
		t.Fatal(err)
	}
}