package pythonlang_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-python/internal/pythonlang"
)

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

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

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

func TestTheEditorColoursPythonSourceItOpens(t *testing.T) {
	// The whole path in one test: Register taught the library about Python, the
	// profile named the editor, and a .py file opened through the public API
	// comes out coloured.
	root := t.TempDir()
	path := filepath.Join(root, "main.py")
	writeFile(t, path, "def main() -> None:\n    pass\n")

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

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

// A Python script in a bin directory has no extension at all, and its first
// line is the only thing that says what it is. That is what Shebangs is for.
func TestAScriptWithNoExtensionIsRecognisedByItsShebang(t *testing.T) {
	root := t.TempDir()
	path := filepath.Join(root, "deploy")
	writeFile(t, path, "#!/usr/bin/env python3\nimport sys\n")

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

	if got := editor.ActiveView().Language(); got != pythonlang.Language {
		t.Errorf("a file starting with a python shebang is coloured as %q, want %q", got, pythonlang.Language)
	}
}

func TestTheEditorDoesNotColourRust(t *testing.T) {
	// "Python instead of Rust" is the whole point of this editor being a
	// separate one: a .rs file opens as plain text here.
	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 != syntax.LanguageNone {
		t.Errorf("a .rs file is coloured as %q; Turbo Python registers Python, not Rust", got)
	}
}

func TestTheToolchainMenuIsCalledPythonAndNoTwoMenusShareAHotKey(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. Python takes P 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 == "Python" {
			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 Python menu on the bar")
	}
}

// --- driven against a real python-lsp-server --------------------------------

// TestCompletionEndToEndWithRealPylsp 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 pylsp is not installed, and under -short.
func TestCompletionEndToEndWithRealPylsp(t *testing.T) {
	root, editor := startRealServer(t)

	// 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 "json." would be answered from disk, and would pass whether or
	// not the editor said anything at all.
	path := filepath.Join(root, "main.py")

	view := editor.ActiveView()
	view.Buffer().SetCursor(buffer.Position{Line: completionLine, Col: 4})
	typeText(editor, "json.")

	// Typing the dot asks for a completion by itself, but a server that is
	// still indexing answers nothing at all. Asking again until it answers is
	// what a person does too.
	if !waitForCompletion(t, editor) {
		t.Fatalf("no completion list opened for %s; the status bar says %q", path, editor.StatusBar().Message())
	}
	if !completionOffers(editor, "loads") {
		t.Errorf("the list does not offer json.loads; it has %d entries", editor.Completion().Count())
	}
}

// Several answers, not one. An earlier version of the library took the first
// location and threw the rest away, so a name used in three places sent you to
// whichever one the server happened to list first.
func TestReferencesAcrossAFileWithRealPylsp(t *testing.T) {
	root, editor := startRealServer(t)
	path := filepath.Join(root, "main.py")

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

	if len(locations) < 3 {
		t.Errorf("helper has %d references, want at least 3 — its declaration and its two call sites: %v",
			len(locations), locations)
	}
}

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

	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"} {
		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 TestDiagnosticsForAFileThatDoesNotParseWithRealPylsp(t *testing.T) {
	root, editor := startRealServer(t)

	broken := filepath.Join(root, "broken.py")
	writeFile(t, broken, "def f(:\n    return 1\n")
	editor.Open(broken)
	editor.Tick()

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

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

// python-lsp-server advertises neither implementationProvider nor
// workspaceSymbolProvider, so two 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 pylsp answers either of
// them, this fails and the page gets revisited.
func TestPylspAnswersNeitherImplementationsNorProjectWideSymbols(t *testing.T) {
	root, editor := startRealServer(t)
	path := filepath.Join(root, "main.py")

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

	if found, err := editor.Language().Implementation(ctx, path, helperLine, helperColumn, helperLineText); err == nil && len(found) > 0 {
		t.Errorf("pylsp now answers implementations (%v); how-to/enable-completion.md says it does not", found)
	}
	if found, err := editor.Language().WorkspaceSymbols(ctx, "helper"); err == nil && len(found) > 0 {
		t.Errorf("pylsp now answers project-wide symbols (%v); how-to/enable-completion.md says it does not", found)
	}
}

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

// realProject is the file every language-server test works against. Line
// numbers are counted from zero and are named by the two constants below, so
// inserting a line here moves them and the constants have to move too.
//
//	 0  import json
//	 1
//	 2
//	 3  def load(text: str) -> object:
//	 4      ← four spaces, and where the completion is typed
//	 5      return json.loads(text)
//	 6
//	 7
//	 8  def helper() -> int:
//	 9      return 1
//	10
//	11
//	12  def first() -> int:
//	13      return helper()
//	…
//
// The line the completion is typed on is deliberately blank on disk but
// indented, so that the cursor can sit where a statement would.
const realProject = "import json\n" +
	"\n" +
	"\n" +
	"def load(text: str) -> object:\n" +
	"    \n" +
	"    return json.loads(text)\n" +
	"\n" +
	"\n" +
	"def helper() -> int:\n" +
	"    return 1\n" +
	"\n" +
	"\n" +
	"def first() -> int:\n" +
	"    return helper()\n" +
	"\n" +
	"\n" +
	"def second() -> int:\n" +
	"    return helper() + 1\n"

// Where the fixture's interesting lines are, counted from zero.
const (
	completionLine = 4
	helperLine     = 8
	helperColumn   = 4
	helperLineText = "def helper() -> int:"
)

// startRealServer writes a project, opens its file, starts pylsp and waits for
// it, in the order the command does. It skips the test when pylsp is missing.
func startRealServer(t *testing.T) (root string, editor *app.App) {
	t.Helper()
	if testing.Short() {
		t.Skip("-short: not starting a language server")
	}

	server, err := lsp.FindServer(pythonlang.Profile().Server)
	if errors.Is(err, lsp.ErrServerNotFound) {
		t.Skipf("%s is not installed; %s", pythonlang.ServerCommand, pythonlang.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", pythonlang.ServerCommand, server, pythonlang.InstallHint)
	}

	root = t.TempDir()
	writeFile(t, filepath.Join(root, "pyproject.toml"),
		"[project]\nname = \"example\"\nversion = \"0.1.0\"\n")
	writeFile(t, filepath.Join(root, "main.py"), realProject)

	editor = newTestEditor(t)

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

	// 2. Start the language server, exactly as main does — afterwards.
	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 Python drawing on a simulated terminal, set up
// the way the command sets it up.
func newTestEditor(t *testing.T) *app.App {
	t.Helper()

	pythonlang.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 := pythonlang.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 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(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 {
	err := exec.Command(path, "--version").Run()
	return err == 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)
	}
}