package rustlang_test

import (
	"context"
	"errors"
	"os"
	"os/exec"
	"path/filepath"
	"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-rust/internal/rustlang"
)

// TestCompletionEndToEndWithRealRustAnalyzer drives the exact sequence the
// command does at start-up: open the files 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 rust-analyzer is not installed, and under -short.
func TestCompletionEndToEndWithRealRustAnalyzer(t *testing.T) {
	if testing.Short() {
		t.Skip("-short: not starting a language server")
	}
	server, err := lsp.FindServer(rustlang.Profile().Server)
	if errors.Is(err, lsp.ErrServerNotFound) {
		t.Skipf("%s is not installed; %s", rustlang.ServerCommand, rustlang.InstallHint)
	}
	// Finding it is not the same as being able to run it. rustup installs a
	// *shim* called rust-analyzer whether or not the component is there, and
	// the shim exits with "Unknown binary 'rust-analyzer' in official
	// toolchain" — after the editor has already started talking to it. The
	// editor reports that on its status bar; a test has nothing to prove
	// against it, so it skips.
	if !serverRuns(server) {
		t.Skipf("%s at %s cannot run; %s", rustlang.ServerCommand, server, rustlang.InstallHint)
	}

	root := t.TempDir()
	writeFile(t, filepath.Join(root, "Cargo.toml"),
		"[package]\nname = \"example\"\nversion = \"0.1.0\"\nedition = \"2021\"\n")

	// The file on disk stops short of the dot. The text the completion is about
	// gets *typed* below, so the answer can only come from what the editor told
	// the server — which is the whole point of this test. A fixture already
	// containing "s." would be answered from disk, and would pass whether or
	// not the editor said anything at all.
	source := "fn main() {\n    let s = String::new();\n    \n}\n"
	path := filepath.Join(root, "src", "main.rs")
	writeFile(t, path, source)

	editor := newTestEditor(t)

	// 1. Open the file, exactly as main does — before there is any server.
	editor.Open(path)

	// 2. Start the language server, exactly as main does — afterwards.
	ctx, cancel := context.WithCancel(t.Context())
	defer 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()

	// 4. Type "s." into the buffer, so that only the editor knows it is there,
	//    then ask for a completion.
	view := editor.ActiveView()
	view.Buffer().SetCursor(buffer.Position{Line: 2, Col: 4})
	typeText(editor, "s.")

	// Typing the dot asks for a completion by itself, but rust-analyzer answers
	// nothing at all until it has finished loading the workspace — and it says
	// so with a $/progress notification this client does not read. Asking again
	// until it answers is what a person does too.
	if !waitForCompletion(t, editor) {
		t.Fatalf("no completion list opened; the status bar says %q", editor.StatusBar().Message())
	}
	if !completionOffers(editor, "len") {
		t.Errorf("the list does not offer String::len; it has %d entries", editor.Completion().Count())
	}
}

func TestTheEditorColoursRustSourceItOpens(t *testing.T) {
	// The whole path in one test: Register taught the library about Rust, the
	// profile named the editor, and a .rs file opened through the public API
	// comes out coloured.
	root := t.TempDir()
	path := filepath.Join(root, "main.rs")
	writeFile(t, path, "fn main() {}\n")

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

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

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

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

func TestTheToolchainMenuIsCalledRustAndNoTwoMenusShareAHotKey(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. Rust takes T because R is Run's and S is
	// Search's, 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 == "Rust" {
			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 Rust menu on the bar")
	}
}

func TestTheEditorDoesNotColourGo(t *testing.T) {
	// "Rust instead of Go" is the whole point of this editor being a separate
	// one: a .go file opens as plain text here.
	root := t.TempDir()
	path := filepath.Join(root, "main.go")
	writeFile(t, path, "package main\n")

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

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

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

	rustlang.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 := rustlang.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):
		}
	}
}

// waitForCompletion asks for a completion until one arrives, or gives up.
//
// rust-analyzer loads the workspace after it has finished initialising, and
// answers 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(90 * 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.
//
// rustup's shim exists on every machine that has rustup, and fails only when
// it is run, so "the file is there" is not the question worth asking.
func serverRuns(path string) bool {
	out, err := exec.Command(path, "--version").CombinedOutput()
	return err == nil && !strings.Contains(string(out), "Unknown binary")
}

// 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)
	}
}