package golang_test

import (
	"context"
	"errors"
	"path/filepath"
	"strings"
	"testing"

	"rickub.com/turbo-editors/turbo-core/lsp"

	"rickub.com/turbo-editors/turbo-go/internal/golang"
)

// TestAgainstRealGopls drives turbo-core's LSP client against an actual
// language server: process, pipes, handshake, completion and shutdown.
//
// It lives here rather than in turbo-core because gopls is Turbo Go's server;
// the library has no language server of its own to test against.
//
// The original comment follows.
//
// It drives the whole client against an actual language
// server: process, pipes, handshake, completion and shutdown.
//
// It is skipped when gopls is not installed and under -short, so a checkout
// with no language server still has a green suite — which is exactly the
// situation the editor itself is built to cope with.
func TestAgainstRealGopls(t *testing.T) {
	if testing.Short() {
		t.Skip("-short: not starting a language server")
	}
	if _, err := lsp.FindServer(golang.Profile().Server); errors.Is(err, lsp.ErrServerNotFound) {
		t.Skipf("%s is not installed; %s", golang.ServerCommand, golang.InstallHint)
	}

	root := t.TempDir()
	writeFile(t, filepath.Join(root, "go.mod"), "module example.test\n\ngo 1.24\n")
	source := "package main\n\nimport \"strings\"\n\nfunc main() {\n\tstrings.\n}\n"
	path := filepath.Join(root, "main.go")
	writeFile(t, path, source)

	server, err := lsp.StartServer(t.Context(), golang.Profile().Server, root, golang.Name)
	if err != nil {
		t.Fatalf("StartServer() error = %v", err)
	}
	client := server.Client()
	t.Cleanup(func() {
		// Not t.Context(): that one is already cancelled by the time cleanups
		// run, and shutting a server down needs a context that is still alive.
		if err := server.Stop(context.Background()); err != nil {
			t.Errorf("Stop() error = %v", err)
		}
	})

	if !client.Ready() {
		t.Fatal("the client is not ready after StartServer returned")
	}
	if err := client.DidOpen(path, source); err != nil {
		t.Fatalf("DidOpen() error = %v", err)
	}

	// Line 5, just after "strings." — the column counts the leading tab as one
	// rune, as the editor does everywhere.
	items, err := client.Complete(t.Context(), path, 5, 9, "\tstrings.")
	if err != nil {
		t.Fatalf("Complete() error = %v", err)
	}
	if len(items) == 0 {
		t.Fatal("gopls offered no completions after \"strings.\"")
	}

	if !containsLabel(items, "Contains") {
		t.Errorf("the completions do not include strings.Contains: %v", labelsOf(items))
	}
}

func containsLabel(items []lsp.CompletionItem, want string) bool {
	for _, item := range items {
		if strings.HasPrefix(item.Label, want) {
			return true
		}
	}
	return false
}

func labelsOf(items []lsp.CompletionItem) []string {
	labels := make([]string, 0, min(len(items), 10))
	for _, item := range items[:min(len(items), 10)] {
		labels = append(labels, item.Label)
	}
	return labels
}