// Copyright 2022 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package bench

import (
	"fmt"
	"sync/atomic"
	"testing"
	"time"

	"golang.org/x/tools/gopls/internal/lsp/fake"
	"golang.org/x/tools/gopls/internal/lsp/protocol"
)

// Use a global edit counter as bench function may execute multiple times, and
// we want to avoid cache hits. Use time.Now to also avoid cache hits from the
// shared file cache.
var editID int64 = time.Now().UnixNano()

var didChangeTests = []struct {
	repo string
	file string
}{
	{"istio", "pkg/fuzz/util.go"},
	{"kubernetes", "pkg/controller/lookup_cache.go"},
	{"kuma", "api/generic/insights.go"},
	{"pkgsite", "internal/frontend/server.go"},
	{"starlark", "starlark/eval.go"},
	{"tools", "internal/lsp/cache/snapshot.go"},
}

// BenchmarkDidChange benchmarks modifications of a single file by making
// synthetic modifications in a comment. It controls pacing by waiting for the
// server to actually start processing the didChange notification before
// proceeding. Notably it does not wait for diagnostics to complete.
func BenchmarkDidChange(b *testing.B) {
	for _, test := range didChangeTests {
		b.Run(test.repo, func(b *testing.B) {
			env := getRepo(b, test.repo).sharedEnv(b)
			env.OpenFile(test.file)
			// Insert the text we'll be modifying at the top of the file.
			env.EditBuffer(test.file, protocol.TextEdit{NewText: "// __REGTEST_PLACEHOLDER_0__\n"})
			env.AfterChange()
			b.ResetTimer()

			for i := 0; i < b.N; i++ {
				edits := atomic.AddInt64(&editID, 1)
				env.EditBuffer(test.file, protocol.TextEdit{
					Range: protocol.Range{
						Start: protocol.Position{Line: 0, Character: 0},
						End:   protocol.Position{Line: 1, Character: 0},
					},
					// Increment the placeholder text, to ensure cache misses.
					NewText: fmt.Sprintf("// __REGTEST_PLACEHOLDER_%d__\n", edits),
				})
				env.Await(env.StartedChange())
			}
		})
	}
}

func BenchmarkDiagnoseChange(b *testing.B) {
	for _, test := range didChangeTests {
		b.Run(test.repo, func(b *testing.B) {
			// Use a new env to avoid the diagnostic delay: we want to measure how
			// long it takes to produce the diagnostics.
			env := getRepo(b, test.repo).newEnv(b, "diagnoseChange", fake.EditorConfig{
				Settings: map[string]interface{}{
					"diagnosticsDelay": "0s",
				},
			})
			defer env.Close()
			env.OpenFile(test.file)
			// Insert the text we'll be modifying at the top of the file.
			env.EditBuffer(test.file, protocol.TextEdit{NewText: "// __REGTEST_PLACEHOLDER_0__\n"})
			env.AfterChange()
			b.ResetTimer()

			// We must use an extra subtest layer here, so that we only set up the
			// shared env once (otherwise we pay additional overhead and the profiling
			// flags don't work).
			b.Run("diagnose", func(b *testing.B) {
				for i := 0; i < b.N; i++ {
					edits := atomic.AddInt64(&editID, 1)
					env.EditBuffer(test.file, protocol.TextEdit{
						Range: protocol.Range{
							Start: protocol.Position{Line: 0, Character: 0},
							End:   protocol.Position{Line: 1, Character: 0},
						},
						// Increment the placeholder text, to ensure cache misses.
						NewText: fmt.Sprintf("// __REGTEST_PLACEHOLDER_%d__\n", edits),
					})
					env.AfterChange()
				}
			})
		})
	}
}