// SPDX-FileCopyrightText: 2026 Coffey Labs
// SPDX-License-Identifier: GPL-3.0-or-later

package preflight

import (
	"context"
	"encoding/json"
	"fmt"
	"net/http"
	"os"
	"path/filepath"
	"strings"
	"testing"

	"github.com/Coffey-Labs/stalwart-migrator/internal/checkpoint"
)

// The defaults the official Stalwart image gives every container made from
// it. A container reporting exactly these has overridden nothing, which is
// the case the image comparison exists to recognise - `docker inspect`
// reports all three either way.
// fakeImageID is the digest inspectDoc reports, and what the fake answers
// `inspect -f {{.Image}}` with. fakeContainerVersion is what running that
// image prints for --version - the same 0.15.5 the fake host binary
// reports, so the docker and binary paths are testing the same migration.
const (
	fakeImageID          = "sha256:0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef"
	fakeContainerVersion = "stalwart 0.15.5"
)

var (
	imageUser       = "stalwart"
	imageEntrypoint = []string{"/usr/local/bin/stalwart"}
	imageCmd        = []string{"--config", "/etc/stalwart/config.json"}
)

// fakeInspect writes a `docker` that answers `inspect` with the given JSON
// document, so the container checks can be exercised without a container.
// `image inspect` answers with the official image's own defaults.
func fakeInspect(t *testing.T, doc string) {
	t.Helper()
	fakeInspectOn(t, doc, imageDoc(t, imageUser, imageEntrypoint, imageCmd))
}

// fakeInspectOn is fakeInspect with the image's defaults named, for the
// tests that need the container and its image to disagree.
func fakeInspectOn(t *testing.T, containerDoc, imgDoc string) {
	t.Helper()
	dir := t.TempDir()
	out := filepath.Join(dir, "inspect.json")
	if err := os.WriteFile(out, []byte(containerDoc), 0o644); err != nil {
		t.Fatal(err)
	}
	img := filepath.Join(dir, "image.json")
	if err := os.WriteFile(img, []byte(imgDoc), 0o644); err != nil {
		t.Fatal(err)
	}
	// Four questions this tool asks docker: the container's definition,
	// the image's defaults, the container's image ID, and what that image
	// reports as its version.
	script := fmt.Sprintf("#!/bin/sh\n"+
		"case \"$1 $2\" in \"image inspect\") cat %q ; exit 0 ;; esac\n"+
		"case \"$1\" in\n"+
		"  inspect) if [ \"$2\" = \"-f\" ]; then echo %q; else cat %q; fi ;;\n"+
		"  run) echo %q ;;\n"+
		"  *) exit 1 ;;\n"+
		"esac\n", img, fakeImageID, out, fakeContainerVersion)
	if err := os.WriteFile(filepath.Join(dir, "docker"), []byte(script), 0o755); err != nil {
		t.Fatal(err)
	}
	t.Setenv("PATH", dir+string(os.PathListSeparator)+os.Getenv("PATH"))
}

func imageDoc(t *testing.T, user string, entrypoint, cmd []string) string {
	t.Helper()
	b, err := json.Marshal([]map[string]any{{
		"Config": map[string]any{"User": user, "Entrypoint": entrypoint, "Cmd": cmd},
	}})
	if err != nil {
		t.Fatal(err)
	}
	return string(b)
}

func inspectDoc(t *testing.T, labels map[string]string, mounts []Mount) string {
	t.Helper()
	doc := []map[string]any{{
		"Name":  "/stalwart",
		"Image": "sha256:0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef",
		"Config": map[string]any{
			"Image": "stalwartlabs/stalwart:v0.15.5", "Labels": labels,
			"User": imageUser, "Entrypoint": imageEntrypoint, "Cmd": imageCmd,
		},
		"State":  map[string]any{"Running": true},
		"Mounts": mounts,
	}}
	b, err := json.Marshal(doc)
	if err != nil {
		t.Fatal(err)
	}
	return string(b)
}

func dataVolume(dest string) Mount {
	return Mount{Type: "volume", Name: "stalwart-data", Destination: dest, RW: true}
}

func TestInspectContainerReadsTheFactsThatMatter(t *testing.T) {
	fakeInspect(t, inspectDoc(t, map[string]string{"com.docker.compose.project": "mail"}, []Mount{dataVolume("/opt/stalwart")}))

	facts, err := InspectContainer(context.Background(), "stalwart")
	if err != nil {
		t.Fatalf("InspectContainer: %v", err)
	}
	if facts.Name != "stalwart" {
		t.Errorf("Name = %q, want stalwart (leading slash stripped)", facts.Name)
	}
	if facts.Image != "stalwartlabs/stalwart:v0.15.5" {
		t.Errorf("Image = %q", facts.Image)
	}
	if facts.ComposeProject() != "mail" {
		t.Errorf("ComposeProject() = %q, want mail", facts.ComposeProject())
	}
	if !facts.Running {
		t.Error("Running = false, want true")
	}
}

// A tag and the digest actually running can disagree - :latest is the
// obvious way, but any moved tag does it. Both are reported because only
// one of them says what is really running.
func TestInspectContainerKeepsTagAndDigestApart(t *testing.T) {
	fakeInspect(t, inspectDoc(t, nil, nil))
	facts, err := InspectContainer(context.Background(), "stalwart")
	if err != nil {
		t.Fatal(err)
	}
	if facts.ImageID == facts.Image {
		t.Error("ImageID and Image should be distinct - one is a tag, the other a digest")
	}
	if got := shortID(facts.ImageID); got != "0123456789ab" {
		t.Errorf("shortID = %q, want 0123456789ab", got)
	}
}

func TestMountForPrefersTheMostSpecificMount(t *testing.T) {
	facts := ContainerFacts{Mounts: []Mount{
		{Type: "bind", Source: "/srv", Destination: "/var/lib", RW: true},
		{Type: "volume", Name: "data", Destination: "/var/lib/stalwart/data", RW: true},
	}}
	m, ok := facts.MountFor("/var/lib/stalwart/data/db")
	if !ok {
		t.Fatal("MountFor found nothing for a path under a mount")
	}
	if m.Name != "data" {
		t.Errorf("MountFor returned %q, want the more specific 'data' mount", m.Name)
	}
	if _, ok := facts.MountFor("/etc/stalwart"); ok {
		t.Error("MountFor matched a path no mount covers")
	}
}

// containerReport runs preflight against a fake container.
func containerReport(t *testing.T, doc string, dataDir string, advisory bool) Report {
	t.Helper()
	for _, p := range systemdUnitPaths {
		if _, err := os.Stat(p); err == nil {
			t.Skipf("host has %s, which detection prefers over docker", p)
		}
	}
	fakeInspect(t, doc)

	counterPath := filepath.Join(t.TempDir(), "invocations")
	binaryPath := writeFakeBinary(t, "0.15.5", counterPath)
	configPath := filepath.Join(t.TempDir(), "config.toml")
	if err := os.WriteFile(configPath, []byte("[server]\nhostname = \"mail.example.com\"\n"), 0o644); err != nil {
		t.Fatal(err)
	}
	withFakeGithub(t, func(w http.ResponseWriter, r *http.Request) {
		json.NewEncoder(w).Encode(Release{TagName: "v0.16.14"})
	})
	store := checkpoint.NewStore(t.TempDir())
	rs, err := store.Create("", "latest")
	if err != nil {
		t.Fatal(err)
	}
	if dataDir == "" {
		dataDir = t.TempDir()
	}
	report, err := New(Options{
		BinaryPath: binaryPath, ConfigPath: configPath, DataDir: dataDir,
		TargetVersion: "latest", ToolCheckAdvisory: true, DeploymentCheckAdvisory: advisory,
	}).Run(context.Background(), store, rs)
	if err != nil {
		t.Fatalf("Run: %v", err)
	}
	return report
}

func resultFor(t *testing.T, r Report, name string) CheckResult {
	t.Helper()
	for _, res := range r.Results {
		if res.Name == name {
			return res
		}
	}
	t.Fatalf("no %q result in report:\n%s", name, r.String())
	return CheckResult{}
}

// A compose-managed container must be refused even once container cutover
// exists: recreating it desyncs the running container from the compose
// file, and the next `compose up` reverts the migration.
func TestComposeManagedContainerIsRefused(t *testing.T) {
	doc := inspectDoc(t, map[string]string{"com.docker.compose.project": "mail"}, []Mount{dataVolume("/opt/stalwart")})
	res := resultFor(t, containerReport(t, doc, "/opt/stalwart", false), "container-runtime")
	if res.Status != StatusFail {
		t.Errorf("container-runtime = %q, want %q\n%s", res.Status, StatusFail, res.Detail)
	}
}

func TestPlainContainerPassesTheRuntimeCheck(t *testing.T) {
	doc := inspectDoc(t, nil, []Mount{dataVolume("/opt/stalwart")})
	res := resultFor(t, containerReport(t, doc, "/opt/stalwart", false), "container-runtime")
	if res.Status != StatusOK {
		t.Errorf("container-runtime = %q, want %q\n%s", res.Status, StatusOK, res.Detail)
	}
}

// Data in the container's own writable layer does not survive the container
// being replaced, and replacing it is what migrating it means.
func TestContainerWithNoWritableMountIsRefused(t *testing.T) {
	doc := inspectDoc(t, nil, nil)
	res := resultFor(t, containerReport(t, doc, "/opt/stalwart", false), "container-data-volume")
	if res.Status != StatusFail {
		t.Errorf("container-data-volume = %q, want %q\n%s", res.Status, StatusFail, res.Detail)
	}
}

// Mounts existing is not the same as the data being on one.
func TestDataDirOutsideEveryMountIsRefused(t *testing.T) {
	doc := inspectDoc(t, nil, []Mount{dataVolume("/opt/stalwart")})
	res := resultFor(t, containerReport(t, doc, "/var/lib/stalwart", false), "container-data-volume")
	if res.Status != StatusFail {
		t.Errorf("container-data-volume = %q, want %q\n%s", res.Status, StatusFail, res.Detail)
	}
}

func TestDataDirOnAVolumePasses(t *testing.T) {
	doc := inspectDoc(t, nil, []Mount{dataVolume("/opt/stalwart")})
	res := resultFor(t, containerReport(t, doc, "/opt/stalwart/data", false), "container-data-volume")
	if res.Status != StatusOK {
		t.Errorf("container-data-volume = %q, want %q\n%s", res.Status, StatusOK, res.Detail)
	}
}

// rehearse has to keep working against a container it cannot migrate -
// that is when its report is most useful - so the same findings are
// advisory there.
func TestRehearseReportsContainerProblemsWithoutBlocking(t *testing.T) {
	doc := inspectDoc(t, map[string]string{"com.docker.compose.project": "mail"}, nil)
	// A real directory, because disk-space stats DataDir on the host. That
	// a container-internal path breaks host-side checks is true and is
	// PR 3's problem (path translation); it is not what this is testing.
	report := containerReport(t, doc, t.TempDir(), true)
	if report.Blocking() {
		t.Fatalf("advisory mode should not block:\n%s", report.String())
	}
	for _, name := range []string{"container-runtime", "container-data-volume"} {
		if got := resultFor(t, report, name).Status; got != StatusWarn {
			t.Errorf("%s = %q, want %q in advisory mode", name, got, StatusWarn)
		}
	}
}

// docker reports Config.User, Cmd and Entrypoint whether the operator set
// them or the image did. A container off the official image reports user
// "stalwart" having been given no --user, and reading that as an operator
// override made this tool refuse to recreate every ordinary Stalwart
// container - at cutover, with the mail already down. Found while checking
// @kaya-eu's field report against a real image.
func TestInspectContainerIgnoresWhatItInheritedFromItsImage(t *testing.T) {
	fakeInspect(t, inspectDoc(t, nil, []Mount{dataVolume("/var/lib/stalwart")}))

	facts, err := InspectContainer(context.Background(), "stalwart")
	if err != nil {
		t.Fatalf("InspectContainer: %v", err)
	}
	if facts.User != "" {
		t.Errorf("User = %q, want empty: it is the image's own USER, not an override", facts.User)
	}
	if len(facts.Cmd) != 0 {
		t.Errorf("Cmd = %v, want none: it is the image's own CMD", facts.Cmd)
	}
	if len(facts.Entrypoint) != 0 {
		t.Errorf("Entrypoint = %v, want none: it is the image's own ENTRYPOINT", facts.Entrypoint)
	}
	if len(facts.Unsupported) != 0 {
		t.Errorf("Unsupported = %v, want none for a plain container off the official image", facts.Unsupported)
	}
}

// The other half of the same distinction: what the operator really did
// override has to be visible, because a recreate that drops it starts
// cleanly as a different server.
func TestInspectContainerReportsWhatTheOperatorOverrode(t *testing.T) {
	doc := inspectDoc(t, nil, []Mount{dataVolume("/var/lib/stalwart")})
	doc = strings.Replace(doc, `"User":"stalwart"`, `"User":"1500:1500"`, 1)
	doc = strings.Replace(doc, `"Cmd":["--config","/etc/stalwart/config.json"]`, `"Cmd":["--config","/srv/mine.toml"]`, 1)
	if strings.Contains(doc, `"User":"stalwart"`) || strings.Contains(doc, "/etc/stalwart/config.json") {
		t.Fatal("the fixture did not take the overrides; the inspect document shape changed")
	}
	fakeInspect(t, doc)

	facts, err := InspectContainer(context.Background(), "stalwart")
	if err != nil {
		t.Fatalf("InspectContainer: %v", err)
	}
	if facts.User != "1500:1500" {
		t.Errorf("User = %q, want the overridden 1500:1500", facts.User)
	}
	if strings.Join(facts.Cmd, " ") != "--config /srv/mine.toml" {
		t.Errorf("Cmd = %v, want the overridden command", facts.Cmd)
	}
	// An entrypoint it did not override still reads as inherited.
	if len(facts.Entrypoint) != 0 {
		t.Errorf("Entrypoint = %v, want none", facts.Entrypoint)
	}
}

// Without the image's defaults there is no way to tell an override from an
// inheritance, and guessing decides what a recreate carries. Same rule as
// a failed container inspect: an error, not an assumption.
func TestInspectContainerRefusesWhenTheImageCannotBeRead(t *testing.T) {
	fakeInspectOn(t, inspectDoc(t, nil, []Mount{dataVolume("/var/lib/stalwart")}), "")

	if _, err := InspectContainer(context.Background(), "stalwart"); err == nil {
		t.Fatal("want an error when the image's defaults cannot be read")
	}
}

// A container-only host has no Stalwart binary, so reading the running
// version from --binary failed preflight's very first check and nothing
// downstream ever ran. What is running is a property of the container's
// image.
func TestPreflightReadsTheSourceVersionFromTheContainersImage(t *testing.T) {
	report := dockerPreflightOn(t, false, nil)
	for _, res := range report.Results {
		if res.Name != "version" {
			continue
		}
		if res.Status != StatusOK {
			t.Fatalf("version status = %q, want %q: %s", res.Status, StatusOK, res.Detail)
		}
		if !strings.Contains(res.Detail, "0.15.5") {
			t.Errorf("version detail should report the image's version, got %q", res.Detail)
		}
		if !strings.Contains(res.Detail, "image behind container") {
			t.Errorf("version detail should say where it read the version, got %q", res.Detail)
		}
		return
	}
	t.Fatalf("no version result in report:\n%s", report.String())
}

// Asking the image by ID rather than by the tag the container was started
// from: a moved tag would report a version nothing is running.
func TestDetectContainerVersionAsksTheImageTheContainerIsOn(t *testing.T) {
	fakeInspect(t, inspectDoc(t, nil, []Mount{dataVolume("/var/lib/stalwart")}))

	got, err := DetectContainerVersion(context.Background(), "stalwart")
	if err != nil {
		t.Fatalf("DetectContainerVersion: %v", err)
	}
	if got != "0.15.5" {
		t.Errorf("DetectContainerVersion = %q, want 0.15.5", got)
	}
}