package builder

import (
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"testing"
)

// A Go program's build source is its import closure (novox/hq ADR 0267 rule 1): never narrower than what
// `go build` reads, whatever the system, the tags, the vendoring or the embeds.

// aGoTree writes files under a fresh directory and returns it.
func aGoTree(t *testing.T, files map[string]string) string {
	t.Helper()
	root := t.TempDir()
	for name, body := range files {
		full := filepath.Join(root, filepath.FromSlash(name))
		if err := os.MkdirAll(filepath.Dir(full), 0o755); err != nil {
			t.Fatal(err)
		}
		if err := os.WriteFile(full, []byte(body), 0o644); err != nil {
			t.Fatal(err)
		}
	}
	return root
}

// aProgram is a module whose program imports its own packages, a vendored module, a local replacement
// that is vendored too, an embed and a package only one system builds; beside them, a package nothing
// imports and one only a test imports.
var aProgram = map[string]string{
	"go.mod": "module example.com/fix\n\ngo 1.22\n\nrequire (\n\texample.org/dep v1.0.0\n\texample.net/local v0.0.0\n)\n\n" +
		"replace example.net/local => ./third_party/local\n",
	"go.sum": "",
	"vendor/modules.txt": "# example.net/local v0.0.0 => ./third_party/local\n## explicit; go 1.22\nexample.net/local/pkg\n" +
		"# example.org/dep v1.0.0\n## explicit; go 1.22\nexample.org/dep\nexample.org/dep/sub\n# example.net/local => ./third_party/local\n",
	"vendor/example.org/dep/dep.go":     "package dep\n\nimport _ \"example.org/dep/sub\"\n",
	"vendor/example.org/dep/sub/sub.go": "package sub\n",
	"vendor/example.org/other/other.go": "package other\n",
	"vendor/example.net/local/pkg/p.go": "package pkg\n",
	"third_party/local/go.mod":          "module example.net/local\n\ngo 1.22\n",
	"third_party/local/pkg/p.go":        "package pkg\n",
	"cmd/prog/main.go": "package main\n\nimport (\n\t\"fmt\"\n\n\t_ \"example.com/fix/emb\"\n\t\"example.com/fix/lib\"\n" +
		"\t_ \"example.net/local/pkg\"\n\t_ \"example.org/dep\"\n)\n\nfunc main() { fmt.Println(lib.X) }\n",
	"lib/lib.go":       "package lib\n\nconst X = 1\n",
	"lib/lib_plan9.go": "//go:build plan9\n\npackage lib\n\nimport _ \"example.com/fix/plan9only\"\n",
	"lib/lib_test.go":  "package lib\n\nimport _ \"example.com/fix/testonly\"\n",
	"lib/lib_amd64.s":  "",
	"lib/sub/sub.go":   "package sub\n",
	"plan9only/p.go":   "package plan9only\n",
	"testonly/t.go":    "package testonly\n",
	"unrelated/u.go":   "package unrelated\n",
	"emb/emb.go": "package emb\n\nimport \"embed\"\n\n//go:embed static/*\nvar Static embed.FS\n\n" +
		"//go:embed \"a b.txt\"\nvar Text string\n",
	"emb/static/index.html":     "x",
	"emb/static/deep/style.css": "x",
	"emb/a b.txt":               "x",
	"README.md":                 "x",
}

func TestAGoProgramsBuildSourceIsItsImportClosure(t *testing.T) {
	root := aGoTree(t, aProgram)
	got, err := GoBuildSource(root, "cmd/prog")
	if err != nil {
		t.Fatal(err)
	}
	for _, c := range []struct {
		file string
		held bool
		why  string
	}{
		{"cmd/prog/main.go", true, "the program itself"},
		{"cmd/prog/helper.go", true, "a file added to the program's package"},
		{"lib/lib.go", true, "a package it imports"},
		{"lib/lib_amd64.s", true, "assembly beside a package's Go"},
		{"lib/lib_plan9.go", true, "a file one system builds"},
		{"plan9only/p.go", true, "what a file one system builds imports"},
		{"emb/static/index.html", true, "an embedded file"},
		{"emb/static/deep/style.css", true, "an embedded file below the pattern's directory"},
		{"emb/a b.txt", true, "an embed named outright, quoted"},
		{"vendor/example.org/dep/dep.go", true, "a vendored package it imports"},
		{"vendor/example.org/dep/sub/sub.go", true, "what a vendored package imports"},
		{"vendor/example.net/local/pkg/p.go", true, "a replaced module, as vendored"},
		{"third_party/local/pkg/p.go", true, "a replaced module, at its directory"},
		{"third_party/local/go.mod", true, "a replaced module's requirements"},
		{"go.mod", true, "the module's requirements"},
		{"go.sum", true, "the module's sums"},
		{"vendor/modules.txt", true, "the vendored modules"},
		{"go.work", true, "a workspace, were one made"},
		{"lib/lib_test.go", false, "a test is not built"},
		{"testonly/t.go", false, "a package only a test imports"},
		{"lib/sub/sub.go", false, "a package below an imported one, not imported"},
		{"unrelated/u.go", false, "a package nothing imports"},
		{"vendor/example.org/other/other.go", false, "a vendored package nothing imports"},
		{"README.md", false, "a file no build reads"},
	} {
		if SourceHolds(got, c.file) != c.held {
			t.Errorf("%s (%s): held %v, wanted %v\n  %v", c.file, c.why, !c.held, c.held, got)
		}
	}

	// **Never narrower than go list -deps**: every package go names, and every file it compiles or embeds,
	// is held. Where no go command is at hand, said, not passed.
	goCmd, err := exec.LookPath("go")
	if err != nil {
		t.Skip("NOT COMPARED: no go command to list the closure with")
	}
	list := exec.Command(goCmd, "list", "-deps", "-f",
		`{{if not .Standard}}{{$d := .Dir}}{{range .GoFiles}}{{$d}}/{{.}}
{{end}}{{range .SFiles}}{{$d}}/{{.}}
{{end}}{{range .EmbedFiles}}{{$d}}/{{.}}
{{end}}{{end}}`, "./cmd/prog")
	list.Dir = root
	list.Env = append(os.Environ(), "GOFLAGS=-mod=vendor", "GOPROXY=off", "GOWORK=off", "GOOS=linux", "GOARCH=amd64")
	out, err := list.CombinedOutput()
	if err != nil {
		t.Fatalf("go list: %v\n%s", err, out)
	}
	real, _ := filepath.EvalSymlinks(root)
	for _, line := range strings.Split(strings.TrimSpace(string(out)), "\n") {
		if line == "" {
			continue
		}
		rel, err := filepath.Rel(real, line)
		if err != nil || strings.HasPrefix(rel, "..") {
			rel, _ = filepath.Rel(root, line)
		}
		if !SourceHolds(got, filepath.ToSlash(rel)) {
			t.Errorf("go list builds %s, and the build source does not hold it", rel)
		}
	}
}

// A file added to the program's import closure moves its build source with it: the closure read again
// grows by the package.
func TestTheBuildSourceGrowsWithAnImport(t *testing.T) {
	files := map[string]string{}
	for k, v := range aProgram {
		files[k] = v
	}
	before, err := GoBuildSource(aGoTree(t, files), "cmd/prog")
	if err != nil {
		t.Fatal(err)
	}
	if SourceHolds(before, "unrelated/u.go") {
		t.Fatal("held before it was imported")
	}
	files["cmd/prog/more.go"] = "package main\n\nimport _ \"example.com/fix/unrelated\"\n"
	after, err := GoBuildSource(aGoTree(t, files), "cmd/prog")
	if err != nil {
		t.Fatal(err)
	}
	if !SourceHolds(after, "unrelated/u.go") {
		t.Fatalf("an import added did not grow the build source: %v", after)
	}
}

// What cannot be read is refused, so the build source is not narrowed and nothing is missed.
func TestABuildSourceThatCannotBeReadIsRefused(t *testing.T) {
	for _, c := range []struct {
		what  string
		files map[string]string
		pkg   string
		says  string
	}{
		{"no go.mod", map[string]string{"cmd/p/main.go": "package main\n"}, "cmd/p", "no go.mod"},
		{"a workspace", map[string]string{"go.mod": "module x\n", "go.work": "go 1.22\n", "p/main.go": "package main\n"},
			"p", "go.work"},
		{"a local replacement outside the tree", map[string]string{
			"go.mod": "module x\n\nreplace y => ../y\n", "p/main.go": "package main\n\nimport _ \"y\"\n"}, "p", "outside"},
		{"a cgo header outside the directory", map[string]string{
			"go.mod": "module x\n", "p/main.go": "package main\n\n// #include \"../h/h.h\"\nimport \"C\"\n"}, "p", "cgo"},
		{"a file that does not parse", map[string]string{"go.mod": "module x\n", "p/main.go": "package main\n\nimport (\n"},
			"p", "main.go"},
		{"a package that leaves the tree", map[string]string{"go.mod": "module x\n"}, "../elsewhere", "leaves"},
	} {
		_, err := GoBuildSource(aGoTree(t, c.files), c.pkg)
		if err == nil || !strings.Contains(err.Error(), c.says) {
			t.Errorf("%s: %v, wanted a refusal saying %q", c.what, err, c.says)
		}
	}
	// A cgo header in the package's own directory is held already, and is no refusal.
	if _, err := GoBuildSource(aGoTree(t, map[string]string{"go.mod": "module x\n",
		"p/main.go": "package main\n\n// #include \"h.h\"\nimport \"C\"\n"}), "p"); err != nil {
		t.Errorf("a header in the package's directory was refused: %v", err)
	}
}

func TestABuildSourceHoldsWhatItsEntriesSay(t *testing.T) {
	entries := []string{"./", "cmd/p/", "web/**", "go.mod"}
	for file, want := range map[string]bool{
		"main.go": true, "main_test.go": false, "cmd/p/x.go": true, "cmd/p/x_test.go": false, "cmd/p/sub/y.go": false,
		"cmd/px/x.go": false, "web/a/b/c.css": true, "web": true, "webx/a": false, "go.mod": true, "docs/x.md": false,
		"/cmd/p/x.go": true, "cmd/p/../q/x.go": false,
	} {
		if SourceHolds(entries, file) != want {
			t.Errorf("%s: held %v, wanted %v", file, !want, want)
		}
	}
	if !SourceHolds([]string{"**"}, "anything/at/all") {
		t.Error("the whole tree does not hold a file")
	}
}

// **A build handed its build source reads nothing else** (rule 3): the narrowed tree holds the source's
// files and no others — never .git — and its fingerprint changes with them and only with them.
func TestANarrowedTreeHoldsTheBuildSourceAndNothingElse(t *testing.T) {
	files := map[string]string{}
	for k, v := range aProgram {
		files[k] = v
	}
	files[".git/HEAD"] = "ref: refs/heads/main\n"
	src := aGoTree(t, files)
	entries, err := GoBuildSource(src, "cmd/prog")
	if err != nil {
		t.Fatal(err)
	}
	dst := filepath.Join(t.TempDir(), "narrow")
	one, err := narrowTree(src, dst, entries)
	if err != nil {
		t.Fatal(err)
	}
	for file, want := range map[string]bool{"cmd/prog/main.go": true, "lib/lib.go": true, "emb/static/deep/style.css": true,
		"lib/lib_test.go": false, "unrelated/u.go": false, "README.md": false, ".git/HEAD": false} {
		_, err := os.Stat(filepath.Join(dst, filepath.FromSlash(file)))
		if (err == nil) != want {
			t.Errorf("%s: copied %v, wanted %v", file, err == nil, want)
		}
	}
	// Outside the build source: one fingerprint.
	files["README.md"] = "changed"
	files["unrelated/u.go"] = "package unrelated\n\nconst Changed = 1\n"
	again, err := narrowTree(aGoTree(t, files), filepath.Join(t.TempDir(), "n"), entries)
	if err != nil || again != one {
		t.Fatalf("a change outside the build source changed its fingerprint: %s %s %v", one, again, err)
	}
	// Inside it: another.
	files["lib/lib.go"] = "package lib\n\nconst X = 2\n"
	moved, err := narrowTree(aGoTree(t, files), filepath.Join(t.TempDir(), "n"), entries)
	if err != nil || moved == one {
		t.Fatalf("a change inside the build source kept its fingerprint: %s %v", moved, err)
	}
}

// This repository's own programs: the route proxy's build source is not the controller's, and neither
// holds the other's command.
func TestThisRepositorysProgramsHaveBuildSourcesOfTheirOwn(t *testing.T) {
	root := filepath.Join("..", "..")
	proxy, err := GoBuildSource(root, "examples/route-proxy")
	if err != nil {
		t.Fatal(err)
	}
	controller, err := GoBuildSource(root, "cmd/mesh-controller")
	if err != nil {
		t.Fatal(err)
	}
	builder, err := GoBuildSource(root, "cmd/mesh-builder")
	if err != nil {
		t.Fatal(err)
	}
	for _, c := range []struct {
		entries []string
		name    string
		file    string
		held    bool
	}{
		{proxy, "the route proxy", "examples/route-proxy/main.go", true},
		{proxy, "the route proxy", "internal/broker/broker.go", true},
		{proxy, "the route proxy", "cmd/mesh-controller/main.go", false},
		{proxy, "the route proxy", "internal/conditions/condition.go", false},
		{proxy, "the route proxy", "README.md", false},
		{controller, "the controller", "cmd/mesh-controller/main.go", true},
		{controller, "the controller", "internal/conditions/condition.go", true},
		{controller, "the controller", "internal/inventory/migrations/0001-nodes.sql", true},
		{controller, "the controller", "examples/route-proxy/main.go", false},
		{controller, "the controller", "cmd/mesh-builder/main.go", false},
		{controller, "the controller", "README.md", false},
		{builder, "the build seat's program", "cmd/mesh-builder/main.go", true},
		{builder, "the build seat's program", "internal/conditions/condition.go", false},
		{builder, "the build seat's program", "cmd/mesh-controller/main.go", false},
	} {
		if SourceHolds(c.entries, c.file) != c.held {
			t.Errorf("%s: %s held %v, wanted %v", c.name, c.file, !c.held, c.held)
		}
	}
}