package gololang_test

import (
	"context"
	"errors"
	"os"
	"os/exec"
	"path/filepath"
	"slices"
	"strings"
	"testing"
	"time"

	"github.com/gdamore/tcell/v2"

	"rickub.com/turbo-editors/turbo-core/app"
	"rickub.com/turbo-editors/turbo-core/buffer"
	"rickub.com/turbo-editors/turbo-core/lsp"
	"rickub.com/turbo-editors/turbo-core/syntax"
	"rickub.com/turbo-editors/turbo-core/ui"

	"rickub.com/turbo-editors/turbo-golo/internal/gololang"
)

// --- the editor, assembled --------------------------------------------------

func TestTheEditorCallsItselfTurboGolo(t *testing.T) {
	editor := newTestEditor(t)

	if got := editor.Profile().Name; got != gololang.Name {
		t.Errorf("Profile().Name = %q, want %q", got, gololang.Name)
	}
	if got := editor.Profile().ProjectDir(); got != ".turbo-golo" {
		t.Errorf("ProjectDir() = %q, want %q", got, ".turbo-golo")
	}
}

func TestTheEditorColoursGoloSourceItOpens(t *testing.T) {
	// The whole path in one test: Register taught the library about Golo, the
	// profile named the editor, and a .golo file opened through the public
	// API comes out coloured.
	root := t.TempDir()
	path := filepath.Join(root, "main.golo")
	writeFile(t, path, "module demo.Main\n\nfunction main = |args| {\n  println(\"hi\")\n}\n")

	editor := newTestEditor(t)
	editor.Open(path)

	if got := editor.ActiveView().Language(); got != gololang.Language {
		t.Fatalf("the view colours the file as %q, want %q", got, gololang.Language)
	}
	if spans := syntax.Highlight(gololang.Language, "function main = |args| {"); len(spans[0]) == 0 {
		t.Error("the registered Golo scanner colours nothing")
	}
}

func TestAScriptWithAShebangAndNoExtensionIsGoloToo(t *testing.T) {
	// A script run as a command has no extension; its first line is what
	// identifies it, and the editor reads that line before choosing a scanner.
	root := t.TempDir()
	path := filepath.Join(root, "greet")
	writeFile(t, path, "#!/usr/bin/env golo\nmodule Greet\n\nfunction main = |args| {\n  println(\"hi\")\n}\n")

	editor := newTestEditor(t)
	editor.Open(path)

	if got := editor.ActiveView().Language(); got != gololang.Language {
		t.Errorf("a script opening with a golo shebang is coloured as %q, want %q", got, gololang.Language)
	}
}

func TestTheEditorDoesNotColourMoonBit(t *testing.T) {
	// "Golo instead of MoonBit" is the whole point of this editor being a
	// separate one: a .mbt file opens as plain text here.
	root := t.TempDir()
	path := filepath.Join(root, "main.mbt")
	writeFile(t, path, "fn main {\n  println(\"hi\")\n}\n")

	editor := newTestEditor(t)
	editor.Open(path)

	if got := editor.ActiveView().Language(); got != syntax.LanguageNone {
		t.Errorf("a .mbt file is coloured as %q; Turbo Golo registers Golo, not MoonBit", got)
	}
}

func TestAProjectsOwnFilesAreStillColouredByTheLibrary(t *testing.T) {
	// A README, a compose file and a Dockerfile are what a Golo project is
	// made of besides its scripts, and turbo-core colours all three without
	// this editor doing anything. That the inherited languages survive
	// registration is worth one test, because syntax.Register writes into
	// package-level state.
	root := t.TempDir()
	editor := newTestEditor(t)

	for name, want := range map[string]syntax.Language{
		"README.md":    syntax.LanguageMarkdown,
		"compose.yaml": syntax.LanguageYAML,
		"Dockerfile":   syntax.LanguageDockerfile,
	} {
		path := filepath.Join(root, name)
		writeFile(t, path, "# heading\n")
		editor.Open(path)

		if got := editor.ActiveView().Language(); got != want {
			t.Errorf("%s is coloured as %q, want %q", name, got, want)
		}
	}
}

func TestTheToolchainMenuIsCalledGoloAndNoTwoMenusShareAHotKey(t *testing.T) {
	// The bar answers the first menu whose hot key matches, so a clash makes
	// one of the two unreachable from the keyboard — silently, and with every
	// other test still passing. Golo takes G because none of the fixed menus
	// does, which is exactly the sort of thing only this test notices.
	editor := newTestEditor(t)

	seen := map[rune]string{}
	found := false
	for _, menu := range editor.MenuBar().Menus() {
		label, hot, _ := ui.SplitHotKey(menu.Label)
		if label == "Golo" {
			found = true
		}
		if hot == 0 {
			t.Errorf("the %q menu has no hot key", label)
			continue
		}
		if other, clash := seen[hot]; clash {
			t.Errorf("%q and %q both answer to Alt-%c", other, label, hot)
		}
		seen[hot] = label
	}
	if !found {
		t.Error("there is no Golo menu on the bar")
	}
}

// --- driven against a real golo lsp -----------------------------------------

// TestCompletionEndToEndWithRealGoloLSP drives the exact sequence the command
// does at start-up: open the file first, start the language server second,
// then ask for a completion.
//
// That order is the whole point, and it is the one Turbo Go got wrong once: an
// editor that announces its open documents to a server which does not exist yet
// and never mentions them again gets answers about a file the server has never
// heard of — which looks, from the outside, exactly like completion not
// working.
//
// It skips itself when golo is not installed, and under -short.
func TestCompletionEndToEndWithRealGoloLSP(t *testing.T) {
	root, editor := startRealServer(t)
	path := filepath.Join(root, "main.golo")

	// Both lines on disk are blank. A function is *declared* by typing, at top
	// level, then its name is typed inside main, so the answer can only come from
	// what the editor told the server — which is the whole point of this
	// test. golo lsp offers keywords and builtins for any file at all, so a
	// completion holding println would prove nothing; a completion holding a
	// function that exists only in the buffer proves the buffer was sent.
	view := editor.ActiveView()
	view.Buffer().SetCursor(buffer.Position{Line: declarationLine, Col: 0})
	typeText(editor, "function zorglub = |x| -> x + 1")
	view.Buffer().SetCursor(buffer.Position{Line: completionLine, Col: 2})
	typeText(editor, "zorg")

	if !waitForCompletion(t, editor) {
		t.Fatalf("no completion list opened for %s; the status bar says %q", path, editor.StatusBar().Message())
	}
	if !completionOffers(editor, "zorglub") {
		t.Errorf("the list does not offer the function typed into the buffer; it has %d entries", editor.Completion().Count())
	}
}

// The scanner's builtin table is read out of GoloScript rather than remembered,
// and this is where that claim is checked against the binary itself: the
// completion golo lsp offers for an empty prefix lists every keyword and every
// builtin it knows, so the two tables can be compared in both directions.
func TestTheScannersTablesMatchWhatTheServerOffers(t *testing.T) {
	root, editor := startRealServer(t)
	path := filepath.Join(root, "main.golo")

	var offered []lsp.CompletionItem
	waitUntil(t, 30*time.Second, func() bool {
		ctx, cancel := context.WithTimeout(t.Context(), 5*time.Second)
		defer cancel()
		items, err := editor.Language().Complete(ctx, path, completionLine, 2, "  ")
		if err != nil {
			return false
		}
		offered = items
		return len(offered) > 0
	})

	labels := map[string]bool{}
	for _, item := range offered {
		labels[item.Label] = true
	}

	for _, builtin := range gololang.Builtins() {
		if !labels[builtin] {
			t.Errorf("the scanner colours %q as a builtin, and golo lsp does not offer it", builtin)
		}
	}
	for _, keyword := range gololang.Keywords() {
		if !labels[keyword] {
			t.Errorf("the scanner colours %q as a keyword, and golo lsp does not offer it", keyword)
		}
	}

	// The other direction: everything the server offers that is not a keyword,
	// a literal or a function the fixture declares must be in the builtin
	// table, or the table has fallen behind the interpreter.
	known := map[string]bool{"true": true, "false": true, "null": true}
	for _, word := range append(gololang.Keywords(), gololang.Builtins()...) {
		known[word] = true
	}
	for _, declared := range []string{"helper", "first", "second", "main"} {
		known[declared] = true
	}
	for label := range labels {
		if !known[label] {
			t.Errorf("golo lsp offers %q, which the scanner knows nothing about", label)
		}
	}
}

func TestGoToDefinitionWithRealGoloLSP(t *testing.T) {
	root, editor := startRealServer(t)
	path := filepath.Join(root, "main.golo")

	locations := waitForLocations(t, func(ctx context.Context) ([]lsp.Location, error) {
		return editor.Language().Definition(ctx, path, callLine, callColumn, callLineText)
	})

	if len(locations) != 1 {
		t.Fatalf("the call to helper has %d definitions, want exactly 1: %v", len(locations), locations)
	}
	if got := locations[0].Range.Start.Line; got != helperLine {
		t.Errorf("the definition of helper is on line %d, want %d", got, helperLine)
	}
}

func TestHoverShowsTheCommentAboveADeclarationWithRealGoloLSP(t *testing.T) {
	// A block of # comments above a declaration is its documentation, and the
	// server shows it on hover. This is what F1 — Code ▸ Describe symbol —
	// draws, and it is the one answer here that carries prose a person wrote.
	root, editor := startRealServer(t)
	path := filepath.Join(root, "main.golo")

	var text string
	waitUntil(t, 30*time.Second, func() bool {
		ctx, cancel := context.WithTimeout(t.Context(), 5*time.Second)
		defer cancel()
		answer, err := editor.Language().Hover(ctx, path, callLine, callColumn, callLineText)
		if err != nil {
			return false
		}
		text = answer
		return text != ""
	})

	if !strings.Contains(text, "Adds one") {
		t.Errorf("hovering helper gave %q, want the comment written above its declaration", text)
	}
}

func TestTheSymbolsOfAFileWithRealGoloLSP(t *testing.T) {
	root, editor := startRealServer(t)
	path := filepath.Join(root, "main.golo")

	var symbols []lsp.Symbol
	waitUntil(t, 30*time.Second, func() bool {
		ctx, cancel := context.WithTimeout(t.Context(), 5*time.Second)
		defer cancel()
		found, err := editor.Language().DocumentSymbols(ctx, path)
		if err != nil {
			return false
		}
		symbols = found
		return len(symbols) > 0
	})

	names := map[string]bool{}
	for _, symbol := range symbols {
		names[symbol.Name] = true
	}
	for _, want := range []string{"helper", "first", "second", "main"} {
		if !names[want] {
			t.Errorf("the file's symbols do not include %q: %v", want, names)
		}
	}
}

// Diagnostics are the one thing a language server sends without being asked,
// and the only feature whose failure looks exactly like success: an editor with
// no error to show and one that cannot find the error are the same blank
// gutter. So this opens a file that does not parse and waits for the mark.
func TestDiagnosticsForAFileThatDoesNotParseWithRealGoloLSP(t *testing.T) {
	root, editor := startRealServerOn(t, brokenScript)
	path := filepath.Join(root, "main.golo")

	waitUntil(t, 30*time.Second, func() bool {
		editor.Tick()
		return len(editor.Language().Diagnostics(path)) > 0
	})

	problems := editor.Language().Diagnostics(path)
	if len(problems) == 0 {
		t.Fatalf("no diagnostic ever arrived for %s; the status bar says %q", path, editor.StatusBar().Message())
	}
	if _, ok := editor.Language().FirstError(path); !ok {
		t.Errorf("the diagnostics hold no error, only %v", problems)
	}
}

// A C-style comment is the mistake everybody coming from another language
// makes, and golo lsp lints it rather than merely failing to parse it. It is
// the diagnostic a new Golo programmer meets first, so it is the one checked
// by name.
func TestACStyleCommentIsDiagnosedWithRealGoloLSP(t *testing.T) {
	root, editor := startRealServerOn(t, "module demo.Lint\n\n// not a Golo comment\nfunction main = |args| {\n  println(\"hi\")\n}\n")
	path := filepath.Join(root, "main.golo")

	waitUntil(t, 30*time.Second, func() bool {
		editor.Tick()
		return len(editor.Language().Diagnostics(path)) > 0
	})

	var messages []string
	for _, problem := range editor.Language().Diagnostics(path) {
		messages = append(messages, problem.Message)
	}
	if !slices.ContainsFunc(messages, func(m string) bool { return strings.Contains(m, "#") }) {
		t.Errorf("the C-style comment was not diagnosed as one; the server said %v", messages)
	}
}

// golo lsp advertises neither referencesProvider, typeDefinitionProvider,
// implementationProvider nor workspaceSymbolProvider, so four of the nine
// questions turbo-core asks come back empty. That is documented in
// how-to/enable-completion.md, and this test is what keeps the documentation
// honest: if a future golo answers any of them, this fails and the page gets
// revisited.
func TestFindReferencesWithRealGoloLSP(t *testing.T) {
	// GoloScript v0.2.0 started answering references. Asked from a call, the
	// answer is the declaration and every call within the file; a use in
	// another file of the same project is not found, because the server
	// resolves nothing across files.
	root, editor := startRealServer(t)
	path := filepath.Join(root, "main.golo")

	locations := waitForLocations(t, func(ctx context.Context) ([]lsp.Location, error) {
		return editor.Language().References(ctx, path, callLine, callColumn, callLineText)
	})

	lines := map[int]bool{}
	for _, location := range locations {
		if !strings.HasSuffix(location.URI, "/main.golo") {
			t.Errorf("a reference points outside the file: %v", location)
		}
		lines[location.Range.Start.Line] = true
	}
	for _, want := range []int{helperLine, callLine, secondCallLine} {
		if !lines[want] {
			t.Errorf("the references to helper miss line %d: %v", want, locations)
		}
	}
	if len(locations) != 3 {
		t.Errorf("helper has %d references, want 3 (the declaration and two calls): %v", len(locations), locations)
	}
}

func TestFindImplementationsWithRealGoloLSP(t *testing.T) {
	// GoloScript v0.2.0 started answering implementations, with the function's
	// declaration: Golo has no interfaces, so a function is its own
	// implementation, and the answer is the same place F12 goes.
	root, editor := startRealServer(t)
	path := filepath.Join(root, "main.golo")

	locations := waitForLocations(t, func(ctx context.Context) ([]lsp.Location, error) {
		return editor.Language().Implementation(ctx, path, callLine, callColumn, callLineText)
	})

	if len(locations) != 1 {
		t.Fatalf("the call to helper has %d implementations, want exactly 1: %v", len(locations), locations)
	}
	if got := locations[0].Range.Start.Line; got != helperLine {
		t.Errorf("the implementation of helper is on line %d, want its declaration on %d", got, helperLine)
	}
}

func TestSymbolsAcrossTheProjectWithRealGoloLSP(t *testing.T) {
	// GoloScript v0.2.0 started answering workspace/symbol. It searches every
	// .golo file under the root, not only the ones the editor has opened, so
	// the second file here is written and never announced to the server.
	root, editor := startRealServer(t)
	writeFile(t, filepath.Join(root, "other.golo"), "module demo.Other\n\nfunction elsewhere = |x| {\n  return x\n}\n")

	find := func(query string) []lsp.Symbol {
		var symbols []lsp.Symbol
		waitUntil(t, 30*time.Second, func() bool {
			ctx, cancel := context.WithTimeout(t.Context(), 5*time.Second)
			defer cancel()
			found, err := editor.Language().WorkspaceSymbols(ctx, query)
			if err != nil {
				return false
			}
			symbols = found
			return len(symbols) > 0
		})
		return symbols
	}

	if symbols := find("helper"); len(symbols) == 0 || symbols[0].Name != "helper" {
		t.Errorf("searching the project for helper gave %v", symbols)
	}
	if symbols := find("elsewhere"); len(symbols) == 0 || symbols[0].Name != "elsewhere" {
		t.Errorf("searching the project for a function in a file the editor never opened gave %v", symbols)
	}
}

func TestGoloLSPDoesNotAnswerTypeDefinitionWithRealGoloLSP(t *testing.T) {
	// The one question of the Code menu the server does not advertise. The
	// documentation says so, and this fails the day a future golo answers it —
	// which is how the three tests above came to exist: until GoloScript
	// v0.2.0 references, implementations and project-wide symbols were refused
	// too, and the test that pinned all four went red on 2026-09-19.
	root, editor := startRealServer(t)
	path := filepath.Join(root, "main.golo")

	ctx, cancel := context.WithTimeout(t.Context(), 15*time.Second)
	defer cancel()

	if found, err := editor.Language().TypeDefinition(ctx, path, helperLine, helperColumn, helperLineText); err == nil && len(found) > 0 {
		t.Errorf("golo lsp now answers type definitions (%v); how-to/enable-completion.md says it does not", found)
	}
}

// --- the fixtures and the waiting -------------------------------------------

// realScript is the file every language-server test works against. Line
// numbers are counted from zero and are named by the constants below, so
// inserting a line here moves them and the constants have to move too.
//
//	 0  module demo.Main
//	 1
//	 2  # Adds one.
//	 3  function helper = |x| {
//	 4    return x + 1
//	 5  }
//	 6
//	 7  function first = |x| {
//	 8    return helper(x)
//	 9  }
//	10
//	11  function second = |x| {
//	12    return helper(x) * 2
//	13  }
//	14  ← where the declaration is typed, at top level: golo lsp offers only
//	15       top-level functions, so one typed inside main would never appear
//	16  function main = |args| {
//	17    let text = "hi"
//	18    ← two spaces, and where the completion is typed
//	19    println(first(1) + second(2) + text)
//	20  }
//
// It runs under golo with no error, which matters: a fixture the interpreter
// complains about would make the diagnostics test pass for the wrong reason.
const realScript = "module demo.Main\n" +
	"\n" +
	"# Adds one.\n" +
	"function helper = |x| {\n" +
	"  return x + 1\n" +
	"}\n" +
	"\n" +
	"function first = |x| {\n" +
	"  return helper(x)\n" +
	"}\n" +
	"\n" +
	"function second = |x| {\n" +
	"  return helper(x) * 2\n" +
	"}\n" +
	"\n" +
	"\n" +
	"function main = |args| {\n" +
	"  let text = \"hi\"\n" +
	"  \n" +
	"  println(first(1) + second(2) + text)\n" +
	"}\n"

// brokenScript is a file that does not parse: the closing brace of main is
// missing. It exists as a second fixture rather than as a line added to the
// first, because a file holding a syntax error is a file whose *other* answers
// are worth nothing: the completion test would then be measuring a parse that
// never finished.
const brokenScript = "module demo.Broken\n" +
	"\n" +
	"function main = |args| {\n" +
	"  let x = (1 +\n"

// Where the fixture's interesting lines are, counted from zero.
const (
	declarationLine = 14
	completionLine  = 18
	helperLine      = 3
	helperColumn    = 9
	helperLineText  = "function helper = |x| {"
	callLine        = 8
	callColumn      = 9
	callLineText    = "  return helper(x)"
	secondCallLine  = 12
)

// startRealServer writes a script, opens it, starts golo lsp and waits for it,
// in the order the command does. It skips the test when golo is missing.
func startRealServer(t *testing.T) (root string, editor *app.App) {
	t.Helper()
	return startRealServerOn(t, realScript)
}

// startRealServerOn is startRealServer over a chosen main.golo.
func startRealServerOn(t *testing.T, source string) (root string, editor *app.App) {
	t.Helper()
	if testing.Short() {
		t.Skip("-short: not starting a language server")
	}

	server, err := lsp.FindServer(gololang.Profile().Server)
	if errors.Is(err, lsp.ErrServerNotFound) {
		t.Skipf("%s is not installed; %s", gololang.ServerCommand, gololang.InstallHint)
	}
	// Finding it is not the same as being able to run it: a shim left behind by
	// a tool manager whose environment has since been removed is on PATH and
	// fails only when started.
	if !serverRuns(server) {
		t.Skipf("%s at %s cannot run; %s", gololang.ServerCommand, server, gololang.InstallHint)
	}

	root = t.TempDir()
	writeFile(t, filepath.Join(root, "main.golo"), source)

	editor = newTestEditor(t)

	// 1. Open the file, exactly as main does — before there is any server.
	editor.Open(filepath.Join(root, "main.golo"))

	// 2. Start the language server, exactly as main does — afterwards, in the
	//    file's own directory, which is what ProjectRoot answers with no
	//    markers.
	ctx, cancel := context.WithCancel(t.Context())
	t.Cleanup(cancel)
	editor.StartLanguageServer(ctx, root)
	t.Cleanup(func() { editor.Language().Stop(context.Background()) })

	waitUntilReady(t, editor)

	// 3. Let the event loop notice the server is ready, as Run does on every
	//    turn. This is what announces the file that was already open.
	editor.Tick()
	return root, editor
}

// newTestEditor returns Turbo Golo drawing on a simulated terminal, set up the
// way the command sets it up.
func newTestEditor(t *testing.T) *app.App {
	t.Helper()

	gololang.Register()
	screen := tcell.NewSimulationScreen("UTF-8")
	if err := screen.Init(); err != nil {
		t.Fatalf("initialising the simulation screen: %v", err)
	}
	t.Cleanup(screen.Fini)
	screen.SetSize(80, 24)

	// Never read the themes or snippets of whoever is running the tests.
	p := gololang.Profile()
	t.Setenv(p.ThemeDirEnvVar(), t.TempDir())
	t.Setenv(p.SnippetDirEnvVar(), t.TempDir())

	editor := app.New(screen, "turbo-classic", p)
	editor.Render()
	return editor
}

// typeText sends a run of printable characters through the whole routing chain.
func typeText(editor *app.App, text string) {
	for _, r := range text {
		editor.Handle(tcell.NewEventKey(tcell.KeyRune, r, tcell.ModNone))
	}
}

// completionOffers reports whether the open popup holds an entry starting with
// a label.
func completionOffers(editor *app.App, label string) bool {
	for _, item := range editor.Completion().Matches() {
		if strings.HasPrefix(item.Label, label) {
			return true
		}
	}
	return false
}

// waitUntilReady blocks until the language server has finished starting.
func waitUntilReady(t *testing.T, editor *app.App) {
	t.Helper()

	deadline := time.After(lsp.InitializeTimeout)
	for !editor.Language().Ready() {
		select {
		case <-deadline:
			t.Fatalf("the language server never became ready: %s", editor.Language().Status())
		case <-time.After(10 * time.Millisecond):
		}
	}
}

// waitUntil polls a condition until it holds or the time runs out, and fails
// the test if it never does.
func waitUntil(t *testing.T, within time.Duration, done func() bool) {
	t.Helper()

	deadline := time.Now().Add(within)
	for time.Now().Before(deadline) {
		if done() {
			return
		}
		time.Sleep(200 * time.Millisecond)
	}
	t.Errorf("the server never answered within %s", within)
}

// waitForLocations asks a location question until it is answered, because a
// server that is still indexing answers an empty list rather than an error.
func waitForLocations(t *testing.T, ask func(context.Context) ([]lsp.Location, error)) []lsp.Location {
	t.Helper()

	var found []lsp.Location
	waitUntil(t, 30*time.Second, func() bool {
		ctx, cancel := context.WithTimeout(t.Context(), 5*time.Second)
		defer cancel()

		locations, err := ask(ctx)
		if err != nil {
			return false
		}
		found = locations
		return len(found) > 0
	})
	return found
}

// waitForCompletion asks for a completion until one arrives, or gives up.
//
// A server may load its state after it has finished initialising, and answer
// an empty list until that is done. There is no notification this client reads
// that says when — so it asks again, which is what the editor's user would do.
func waitForCompletion(t *testing.T, editor *app.App) bool {
	t.Helper()

	deadline := time.Now().Add(60 * time.Second)
	for time.Now().Before(deadline) {
		if editor.Completion().Visible() {
			return true
		}
		editor.RequestCompletion()
		if editor.Completion().Visible() {
			return true
		}
		time.Sleep(500 * time.Millisecond)
	}
	return false
}

// serverRuns reports whether the language server at path actually starts.
func serverRuns(path string) bool {
	return exec.Command(path, "--version").Run() == nil
}

// writeFile creates a file, making its directory first.
func writeFile(t *testing.T, path, content string) {
	t.Helper()
	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
		t.Fatalf("creating %s: %v", filepath.Dir(path), err)
	}
	if err := os.WriteFile(path, []byte(content), 0o644); err != nil {
		t.Fatalf("writing %s: %v", path, err)
	}
}