package builder

import (
	"context"
	"os"
	"path/filepath"
	"strings"
	"testing"
	"time"

	"github.com/novox/mesh-controller/internal/catalogue"
)

// A repository becoming artifacts the mesh can pin.
//
// git and docker are injected rather than run, because what is under test is the ORDER and the
// refusals — that nothing is published until everything is built, that a build reads only its own
// tree, that two builds of one commit produce one digest. Running docker here would test docker.

type recorded struct {
	ran      []string
	images   map[string]string
	archives map[string]string
	failPush bool
	// contents is what a clone of this repository lands, so the fake clone can restore the tree
	// Build deliberately removes first.
	contents map[string]string
	// stamped is the modification time the clone gives every file. Set differently between two
	// builds of one commit, because otherwise both land in the same second and a packer that
	// carried timestamps would still produce one digest — which is a test that passes for a
	// reason that has nothing to do with what it claims.
	stamped time.Time
}

func (r *recorded) run(_ context.Context, dir, name string, args ...string) (string, error) {
	line := name + " " + strings.Join(args, " ")
	r.ran = append(r.ran, line)
	switch {
	case name == "git" && len(args) > 0 && args[0] == "clone":
		tree := args[len(args)-1]
		if err := os.MkdirAll(tree, 0o755); err != nil {
			return "", err
		}
		for path, body := range r.contents {
			full := filepath.Join(tree, path)
			if err := os.MkdirAll(filepath.Dir(full), 0o755); err != nil {
				return "", err
			}
			if err := os.WriteFile(full, []byte(body), 0o644); err != nil {
				return "", err
			}
			if !r.stamped.IsZero() {
				if err := os.Chtimes(full, r.stamped, r.stamped); err != nil {
					return "", err
				}
			}
		}
		return "", nil
	case name == "git" && len(args) > 0 && args[0] == "rev-parse":
		return "c0ffeec0ffeec0ffeec0ffeec0ffeec0ffeec0ff\n", nil
	}
	_ = dir
	return "", nil
}

func (r *recorded) PublishImage(_ context.Context, localTag, repository string) (string, error) {
	if r.failPush {
		return "", os.ErrPermission
	}
	if r.images == nil {
		r.images = map[string]string{}
	}
	r.images[repository] = localTag
	return "registry.invalid/" + repository + "@sha256:" + strings.Repeat("a", 64), nil
}

func (r *recorded) PublishArchive(_ context.Context, repository string, body []byte, digest string) (string, error) {
	if r.failPush {
		return "", os.ErrPermission
	}
	if r.archives == nil {
		r.archives = map[string]string{}
	}
	r.archives[repository] = digest
	_ = body
	return "https://store.invalid/" + repository, nil
}

// aRepository is a workspace whose clone lands a manifest and some files.
func aRepository(t *testing.T, manifest string, files map[string]string) (*recorded, string) {
	t.Helper()
	contents := map[string]string{ManifestName: manifest}
	for name, body := range files {
		contents[name] = body
	}
	return &recorded{contents: contents}, t.TempDir()
}

const withBoth = `{"module":"meshboard","version":"1",
  "build":{"artifacts":[
    {"name":"server","kind":"image","from":"Dockerfile"},
    {"name":"look","kind":"archive","from":"files"}]},
  "resources":[
    {"id":"svc","type":"container","name":"meshboard","artifact":"server"},
    {"id":"theme","type":"archive","path":"/opt/meshboard","artifact":"look"}]}`

func TestABuildProducesAManifestThePinsAreIn(t *testing.T) {
	r, workspace := aRepository(t, withBoth, map[string]string{
		"Dockerfile": "FROM scratch", "files/theme.conf": "dark",
	})
	got, err := Build(context.Background(), r.run, r, "https://forge.invalid/meshboard.git", "", "", workspace, nil, Npmrc{}, nil)
	if err != nil {
		t.Fatal(err)
	}
	if got.Commit != "c0ffeec0ffeec0ffeec0ffeec0ffeec0ffeec0ff" {
		t.Fatalf("the commit was not recorded: %q", got.Commit)
	}
	if got.Manifest.Resources[0]["image"] == nil {
		t.Fatalf("the image was not pinned: %v", got.Manifest.Resources[0])
	}
	digest, _ := got.Manifest.Resources[1]["digest"].(string)
	if !strings.HasPrefix(digest, "sha256:") {
		t.Fatalf("the archive was not pinned: %v", got.Manifest.Resources[1])
	}
}

func TestTwoBuildsOfOneCommitProduceOneDigest(t *testing.T) {
	// Or nothing downstream can tell "this changed" from "this was built again", and every
	// rebuild looks like a change to every machine holding it.
	var digests []string
	for i := 0; i < 2; i++ {
		r, workspace := aRepository(t, withBoth, map[string]string{
			"Dockerfile": "FROM scratch", "files/a.conf": "one", "files/b.conf": "two",
		})
		// A year apart, so a packer carrying timestamps cannot accidentally agree.
		r.stamped = time.Date(2020+i, time.March, 3, 4, 5, 6, 0, time.UTC)
		got, err := Build(context.Background(), r.run, r, "https://forge.invalid/x.git", "", "", workspace, nil, Npmrc{}, nil)
		if err != nil {
			t.Fatal(err)
		}
		for _, b := range got.Built {
			if b.Kind == catalogue.ArtifactArchive {
				digests = append(digests, b.Digest)
			}
		}
	}
	if digests[0] != digests[1] {
		t.Fatalf("two builds of one commit produced %s and %s", digests[0], digests[1])
	}
}

func TestNothingIsPublishedUntilEverythingIsBuilt(t *testing.T) {
	// Half a module in the store under a digest the mesh never records is reachable,
	// unreferenced, and indistinguishable from something in use.
	r, workspace := aRepository(t, withBoth, map[string]string{"Dockerfile": "FROM scratch"})
	// `files` is missing, so packing the archive fails — after the image would have been pushed.
	_, err := Build(context.Background(), r.run, r, "https://forge.invalid/x.git", "", "", workspace, nil, Npmrc{}, nil)
	if err == nil {
		t.Fatal("a build with a missing input succeeded")
	}
	if len(r.archives) != 0 {
		t.Fatalf("an archive was published by a failed build: %v", r.archives)
	}
}

func TestARepositoryWithNoManifestSaysSo(t *testing.T) {
	workspace := t.TempDir()
	r := &recorded{contents: map[string]string{"README.md": "nothing to see"}}
	_, err := Build(context.Background(), r.run, r, "https://forge.invalid/x.git", "", "", workspace, nil, Npmrc{}, nil)
	if err == nil {
		t.Fatal("a repository with nothing saying what it is was built")
	}
	if !strings.Contains(err.Error(), ManifestName) {
		t.Fatalf("the failure does not name what is missing: %v", err)
	}
}

func TestAModuleThatBuildsNothingStillProducesAManifest(t *testing.T) {
	// Most of what a person installs is configuration.
	r, workspace := aRepository(t, `{"module":"shell","version":"1","resources":[
		{"id":"rc","type":"file","path":"/etc/zsh/zshrc","content":"setopt"}]}`, nil)
	got, err := Build(context.Background(), r.run, r, "https://forge.invalid/shell.git", "", "", workspace, nil, Npmrc{}, nil)
	if err != nil {
		t.Fatal(err)
	}
	if len(got.Built) != 0 {
		t.Fatalf("something was built: %v", got.Built)
	}
	if got.Manifest.Module != "shell" || len(got.Manifest.Resources) != 1 {
		t.Fatalf("got %+v", got.Manifest)
	}
	for _, line := range r.ran {
		if strings.HasPrefix(line, "docker") {
			t.Fatalf("docker was run for a module that builds nothing: %q", line)
		}
	}
}

func TestTheTreeIsFreshEveryTime(t *testing.T) {
	// A build that reuses a working tree can succeed because of something a previous build left
	// behind, and that is a build nobody can reproduce.
	r, workspace := aRepository(t, withBoth, map[string]string{
		"Dockerfile": "FROM scratch", "files/a": "b",
	})
	leftover := filepath.Join(workspace, "source", "files", "from-last-time")
	if err := os.MkdirAll(filepath.Dir(leftover), 0o755); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(leftover, []byte("stale"), 0o644); err != nil {
		t.Fatal(err)
	}
	if _, err := Build(context.Background(), r.run, r, "https://forge.invalid/x.git", "", "", workspace, nil, Npmrc{}, nil); err != nil {
		t.Fatal(err)
	}
	if _, err := os.Stat(leftover); err == nil {
		t.Fatal("a previous build's file survived into this one")
	}
}

func TestABuildThatCannotPushFails(t *testing.T) {
	r, workspace := aRepository(t, withBoth, map[string]string{
		"Dockerfile": "FROM scratch", "files/a": "b",
	})
	r.failPush = true
	if _, err := Build(context.Background(), r.run, r, "https://forge.invalid/x.git", "", "", workspace, nil, Npmrc{}, nil); err == nil {
		t.Fatal("a build that could publish nothing reported success")
	}
}

func TestAnUpstreamImageIsMirroredRatherThanBuilt(t *testing.T) {
	// A module usually runs software it did not write. Naming the upstream reference directly
	// would need every machine to reach a public registry, and would pin to a tag somebody else
	// can move.
	const mirrors = `{"module":"postgres","version":"1",
	  "build":{"artifacts":[{"name":"store","kind":"upstream","from":"postgres:17-alpine"}]},
	  "resources":[{"id":"db","type":"container","name":"mesh-postgres","artifact":"store"}]}`

	r, workspace := aRepository(t, mirrors, nil)
	got, err := Build(context.Background(), r.run, r, "https://forge.invalid/postgres.git", "", "", workspace, nil, Npmrc{}, nil)
	if err != nil {
		t.Fatal(err)
	}
	// Pulled, not built.
	var pulled, built bool
	for _, line := range r.ran {
		if strings.HasPrefix(line, "docker pull postgres:17-alpine") {
			pulled = true
		}
		if strings.HasPrefix(line, "docker build") {
			built = true
		}
	}
	if !pulled {
		t.Fatalf("the upstream image was not fetched: %v", r.ran)
	}
	if built {
		t.Fatalf("something was built for an image that is mirrored: %v", r.ran)
	}
	// And the resource names what this registry serves, pinned by the digest it assigned.
	image, _ := got.Manifest.Resources[0]["image"].(string)
	if !strings.Contains(image, "@sha256:") {
		t.Fatalf("the mirrored image is not pinned by digest: %q", image)
	}
	if strings.Contains(image, "17-alpine") {
		t.Fatalf("the resource still names the upstream tag: %q", image)
	}
}

func TestAnUpstreamImageWithNoTagIsRefused(t *testing.T) {
	// What gets mirrored would be whatever `latest` means today, and a module pinned to that is
	// not pinned.
	_, err := catalogue.ParseManifest([]byte(`{"module":"a","version":"1","build":{"artifacts":[
		{"name":"x","kind":"upstream","from":"postgres"}]}}`))
	if err == nil {
		t.Fatal("an untagged upstream reference was accepted")
	}
	if !strings.Contains(err.Error(), "no tag or digest") {
		t.Fatalf("unhelpful refusal: %v", err)
	}
}

func TestAnUpstreamReferenceIsNotAPathInTheRepository(t *testing.T) {
	// The rule that a build reads only its own repository must not refuse every reference with a
	// registry host in it.
	if _, err := catalogue.ParseManifest([]byte(`{"module":"a","version":"1","build":{"artifacts":[
		{"name":"x","kind":"upstream","from":"registry.example/library/postgres:17"}]}}`)); err != nil {
		t.Fatalf("a perfectly ordinary upstream reference was refused: %v", err)
	}
}

// **A module is a repository and a path within it** (novox/hq ADR 0069). The catalogue holds its
// modules one to a directory and the system this replaces has always built one that way, so a
// builder that could only read a repository's root could build none of what exists.
func TestAModuleIsBuiltFromItsPathWithinTheRepository(t *testing.T) {
	r := &recorded{contents: map[string]string{
		"README.md":                      "this repository holds several modules",
		"modules/shell/" + ManifestName:  withBoth,
		"modules/shell/Dockerfile":       "FROM scratch",
		"modules/shell/files/theme.conf": "dark",
		// A second module beside it, so what is built is chosen by the path rather than by
		// happening to be the only manifest in the clone.
		"modules/other/" + ManifestName: `{"module":"other","version":"1"}`,
	}}
	got, err := Build(context.Background(), r.run, r,
		"https://forge.invalid/catalogue.git", "modules/shell", "", t.TempDir(), nil, Npmrc{}, nil)
	if err != nil {
		t.Fatal(err)
	}
	if got.Manifest.Module != "meshboard" {
		t.Fatalf("built %q, which is not the module at the path asked for", got.Manifest.Module)
	}
	if got.Manifest.Resources[0]["image"] == nil {
		t.Fatalf("the image was not pinned: %v", got.Manifest.Resources[0])
	}
}

// A build reads only its own tree. A path climbing out of the clone would otherwise let a build
// read — and an archive artifact publish — whatever the build machine happens to hold, which is
// the one thing a machine that builds other people's repositories must not do.
func TestAPathThatLeavesTheRepositoryIsRefused(t *testing.T) {
	for _, escaping := range []string{"../../etc", "/etc"} {
		r := &recorded{contents: map[string]string{ManifestName: withBoth}}
		_, err := Build(context.Background(), r.run, r,
			"https://forge.invalid/x.git", escaping, "", t.TempDir(), nil, Npmrc{}, nil)
		if err == nil {
			t.Fatalf("%q was accepted as a module's path", escaping)
		}
		if !strings.Contains(err.Error(), "leaves the repository") &&
			!strings.Contains(err.Error(), "absolute path") {
			t.Fatalf("the refusal of %q does not say why: %v", escaping, err)
		}
	}
}