package server

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

// Guards the version derivation that stamps every build.
//
// These assertions used to be impossible to run. The derivation lived inline
// in release.yml, which triggers only on `main` and on tags — so a mistake in
// it could not surface until a release was already under way, and its failure
// mode is silence: a version nobody can compare looks exactly like being up to
// date, and nobody reports an update they were never offered.
//
// Moving it to ci/version.sh made it executable, so this runs on every push
// that touches the release machinery. That is the whole point of the file; the
// specific assertions below matter less than the fact that they run at all.
//
// The tests EXECUTE the script rather than asserting on its text, so they
// break when the behaviour changes rather than when the wording does.

// highestOldSchemeCode is the largest versionCode ever shipped under the
// retired commit-count scheme (v2026.09.09 shipped 1895). Every code the new
// scheme emits must clear it, or Android would refuse the upgrade as a
// downgrade and the update channel would be a one-way door.
const highestOldSchemeCode = 1895

func repoRoot(t *testing.T) string {
	t.Helper()
	dir, err := os.Getwd()
	if err != nil {
		t.Fatal(err)
	}
	for {
		if _, err := os.Stat(filepath.Join(dir, "go.mod")); err == nil {
			return dir
		}
		parent := filepath.Dir(dir)
		if parent == dir {
			t.Fatalf("no go.mod above %s", dir)
		}
		dir = parent
	}
}

// runVersion executes ci/version.sh with both clocks pinned, so the result is
// deterministic. Returns the parsed KEY=VALUE output.
func runVersion(t *testing.T, commitEpoch, nowEpoch string) map[string]string {
	t.Helper()
	out, err := versionScript(t, commitEpoch, nowEpoch)
	if err != nil {
		t.Fatalf("ci/version.sh failed: %v\n%s", err, out)
	}
	parsed := map[string]string{}
	for _, line := range strings.Split(strings.TrimSpace(out), "\n") {
		if k, v, ok := strings.Cut(line, "="); ok {
			parsed[k] = v
		}
	}
	return parsed
}

func versionScript(t *testing.T, commitEpoch, nowEpoch string) (string, error) {
	t.Helper()
	root := repoRoot(t)
	cmd := exec.Command(filepath.Join(root, "ci", "version.sh"))
	cmd.Dir = root
	cmd.Env = append(os.Environ(),
		"MINSTREL_COMMIT_EPOCH="+commitEpoch,
		"MINSTREL_NOW_EPOCH="+nowEpoch,
	)
	out, err := cmd.CombinedOutput()
	return string(out), err
}

func TestVersionName_IsCommitTimeToTheMinute(t *testing.T) {
	// 2025-09-09T18:48:56Z
	got := runVersion(t, "1757443736", "1789000920")
	if want := "2025.09.09.1848"; got["name"] != want {
		t.Errorf("name = %q, want %q", got["name"], want)
	}
}

// HHMM is the segment most likely to be silently mangled, and it only bites
// for about a tenth of the day — a build just after midnight must emit "0042",
// never "42". A stripped leading zero shifts the segment by two orders of
// magnitude and reverses comparisons against every other build that day.
func TestVersionName_PadsTheMinuteSegment(t *testing.T) {
	// 2026-09-10T00:42:00Z
	got := runVersion(t, "1789000920", "1789000920")
	if want := "2026.09.10.0042"; got["name"] != want {
		t.Errorf("name = %q, want %q — leading zero lost?", got["name"], want)
	}
}

func TestVersionName_DerivesFromCommitNotBuildClock(t *testing.T) {
	// Same commit, two different build clocks: the NAME must not move, or a
	// dev build and a main build of one commit would report different strings
	// and the channel field would stop being the only thing separating them.
	a := runVersion(t, "1757443736", "1789000920")
	b := runVersion(t, "1757443736", "1789500000")
	if a["name"] != b["name"] {
		t.Errorf("name moved with the build clock: %q vs %q", a["name"], b["name"])
	}
	if a["code"] == b["code"] {
		t.Errorf("code did NOT move with the build clock (%q) — it is not build-derived", a["code"])
	}
}

func TestVersionCode_IsMinutesSince2020AndClearsTheOldScheme(t *testing.T) {
	got := runVersion(t, "1789000920", "1789000920")
	code, err := strconv.Atoi(got["code"])
	if err != nil {
		t.Fatalf("code %q is not an integer: %v", got["code"], err)
	}
	if want := (1789000920 - 1577836800) / 60; code != want {
		t.Errorf("code = %d, want %d", code, want)
	}
	if code <= highestOldSchemeCode {
		t.Errorf("code %d does not clear the retired commit-count scheme (%d) — "+
			"Android would refuse the upgrade as a downgrade", code, highestOldSchemeCode)
	}
	if int64(code) > 2147483647 {
		t.Errorf("code %d overflows versionCode's int32 ceiling", code)
	}
}

// The tag is not chosen, it is the name with a `v`. Anything else reintroduces
// the mismatch between what a tag claims and what the artifact reports.
func TestTag_IsTheNameWithAPrefix(t *testing.T) {
	got := runVersion(t, "1757443736", "1789000920")
	if want := "v" + got["name"]; got["tag"] != want {
		t.Errorf("tag = %q, want %q", got["tag"], want)
	}
}

// A guard that cannot fail is worse than no guard. These prove the script
// rejects the shapes it claims to reject, rather than emitting something
// plausible and letting it ship.
func TestVersionScript_RejectsUnusableClocks(t *testing.T) {
	for _, tc := range []struct{ name, commit, now string }{
		{"unreadable commit timestamp", "notanumber", "1789000920"},
		{"non-numeric build clock", "1789000920", "abc"},
		{"build clock before 2020", "1789000920", "1000000000"},
	} {
		t.Run(tc.name, func(t *testing.T) {
			out, err := versionScript(t, tc.commit, tc.now)
			if err == nil {
				t.Errorf("script succeeded on %s, output: %s", tc.name, out)
			}
		})
	}
}

// Pins the wiring, not the formula: if release.yml stops calling the script,
// every assertion above keeps passing while the thing that actually ships goes
// unguarded again. That silent decoupling is the specific regression here.
func TestReleaseWorkflow_UsesTheSharedDerivation(t *testing.T) {
	body, err := os.ReadFile(filepath.Join(repoRoot(t), ".gitea", "workflows", "release.yml"))
	if err != nil {
		t.Fatal(err)
	}
	yaml := string(body)

	if !strings.Contains(yaml, "ci/version.sh") {
		t.Error("release.yml no longer calls ci/version.sh — the derivation has drifted out of test coverage")
	}
	// The retired scheme, which must not come back. A presence check is safe
	// against prose; the historical note in that file names the old formula
	// only in comments, so match the executable form.
	if strings.Contains(yaml, "$(git rev-list --count") {
		t.Error("release.yml derives a commit count again — that is not monotonic across branches")
	}
}

// jobBoundary matches a blank line followed by job-level (two-space)
// indentation — the end of the last step in a job.
var jobBoundary = regexp.MustCompile(`\n\n  [^ \n]`)

// stepBody returns one workflow step's text, from its `- name:` line to the
// start of the next step or the next job.
//
// The naive cut — "up to the next `- name:`" — silently returns an EMPTY body
// for the last step in a job, and every assertion over it then passes
// vacuously. That is the failure rule 167 names: a check that reads as
// coverage while asserting on nothing. Cutting at a blank line followed by
// job-level indentation handles the last-step case, which is exactly where
// `Build and push` sits.
func stepBody(t *testing.T, yaml, name string) string {
	t.Helper()
	i := strings.Index(yaml, "- name: "+name)
	if i < 0 {
		t.Fatalf("no %q step in release.yml", name)
	}
	body := yaml[i:]
	end := len(body)
	if j := strings.Index(body, "\n      - name:"); j >= 0 {
		end = j
	}
	// A blank line followed by EXACTLY two spaces and then content starts a
	// new job or job-level comment. The "exactly" matters: a blank line inside
	// a `run:` block is followed by ten-space indentation and would otherwise
	// match, truncating the step mid-body — which is how this helper first
	// sliced the verify step down to its first two lines.
	if loc := jobBoundary.FindStringIndex(body); loc != nil && loc[0] < end {
		end = loc[0]
	}
	body = body[:end]
	if strings.TrimSpace(strings.TrimPrefix(body, "- name: "+name)) == "" {
		t.Fatalf("step %q sliced to an empty body — the assertions below would pass vacuously", name)
	}
	return body
}

// releaseYAML reads the workflow once per test.
func releaseYAML(t *testing.T) string {
	t.Helper()
	body, err := os.ReadFile(filepath.Join(repoRoot(t), ".gitea", "workflows", "release.yml"))
	if err != nil {
		t.Fatal(err)
	}
	return string(body)
}

// imageTagArms splits "Compute image tags" into its three ref branches. The
// whole tag policy lives in that if/elif/else, so the arms are the unit worth
// asserting on — a tag published from the wrong arm reaches the wrong
// audience, and every such mistake still builds and still pushes a valid
// image.
func imageTagArms(t *testing.T, yaml string) (tagArm, devArm, mainArm string) {
	t.Helper()
	const (
		tagMarker  = `if [[ "${GITHUB_REF}" == refs/tags/v* ]]; then`
		devMarker  = `elif [[ "${GITHUB_REF}" == "refs/heads/dev" ]]; then`
		mainMarker = "\n          else"
		endMarker  = "\n          fi"
	)
	iTag := strings.Index(yaml, tagMarker)
	iDev := strings.Index(yaml, devMarker)
	iMain := -1
	if iDev >= 0 {
		if k := strings.Index(yaml[iDev:], mainMarker); k >= 0 {
			iMain = iDev + k
		}
	}
	if iTag < 0 || iDev < 0 || iMain < 0 {
		t.Fatal("Compute image tags no longer has a tag/dev/main arm — the tag policy has been restructured, so these guards are pinning nothing")
	}
	iEnd := iMain
	if k := strings.Index(yaml[iMain:], endMarker); k >= 0 {
		iEnd = iMain + k
	} else {
		t.Fatal("no closing fi after the main arm")
	}
	return yaml[iTag:iDev], yaml[iDev:iMain], yaml[iMain:iEnd]
}

// The worst regression this wiring can produce: a dev push that also moves
// :latest would ship untested code to every stable operator, silently, on the
// next pull. Nothing else in the suite would notice — the build stays green
// and the image is valid, it is simply the wrong audience.
func TestDevChannel_PublishesDevAloneAndNeverLatest(t *testing.T) {
	_, arm, _ := imageTagArms(t, releaseYAML(t))

	if !strings.Contains(arm, "${IMAGE}:dev") {
		t.Errorf("dev arm does not publish :dev\n%s", arm)
	}
	if strings.Contains(arm, ":latest") {
		t.Errorf("dev arm moves :latest — that ships dev code to every stable operator\n%s", arm)
	}
	// Rule 145: a rolling channel gets no commit-addressable tag.
	if strings.Contains(arm, "GITHUB_SHA") {
		t.Errorf("dev arm publishes a per-commit tag; a rolling channel should not\n%s", arm)
	}
}

// The two bundling paths must stay mutually exclusive. If the rebundle step's
// condition were relaxed back to "not a tag", a dev push would run BOTH: stage
// its freshly-built APK, then overwrite it with the previous release's. The
// image would still build and the sidecar would still parse — it would just
// quietly serve stale art to the channel whose whole job is being current.
func TestDevChannel_RebundlePathIsMainOnly(t *testing.T) {
	body, err := os.ReadFile(filepath.Join(repoRoot(t), ".gitea", "workflows", "release.yml"))
	if err != nil {
		t.Fatal(err)
	}
	yaml := string(body)

	i := strings.Index(yaml, "- name: Bundle latest release APK")
	if i < 0 {
		t.Fatal("no 'Bundle latest release APK' step")
	}
	step := yaml[i:]
	if j := strings.Index(step, "\n      - name:"); j >= 0 {
		step = step[:j]
	}
	if !strings.Contains(step, "github.ref == 'refs/heads/main'") {
		t.Errorf("the rebundle step is not gated to main; a dev push would overwrite its own APK\n%s", step)
	}
}

// The runner invokes `shell: bash` as `bash -e -o pipefail`. That makes any
// command substitution whose grep matches NOTHING fatal at the assignment —
// pipefail reports the grep's non-zero status even though `head` succeeded —
// so the step dies before reaching the `if` written to handle the empty case.
//
// This is not hypothetical. It took down the first `main` build after the
// version rework: the newest release predated sidecar assets, its
// `.apk.version` grep matched nothing, and the step aborted instead of
// falling through to the name-only branch that exists precisely for it. The
// same latent hazard sat on the other two assignments and had simply never
// fired, because their greps always matched.
//
// Pins the property that makes every "degrades gracefully" branch in that
// step reachable at all.
func TestBundleStep_GrepsCannotKillTheStep(t *testing.T) {
	body, err := os.ReadFile(filepath.Join(repoRoot(t), ".gitea", "workflows", "release.yml"))
	if err != nil {
		t.Fatal(err)
	}
	yaml := string(body)

	i := strings.Index(yaml, "- name: Bundle latest release APK")
	if i < 0 {
		t.Fatal("no 'Bundle latest release APK' step")
	}
	step := yaml[i:]
	if j := strings.Index(step, "\n      - name:"); j >= 0 {
		step = step[:j]
	}

	for _, line := range strings.Split(step, "\n") {
		trimmed := strings.TrimSpace(line)
		if strings.HasPrefix(trimmed, "#") || !strings.Contains(trimmed, "grep") {
			continue
		}
		// Only assignments from a command substitution can abort the step.
		if !strings.Contains(trimmed, `="$(`) {
			continue
		}
		if !strings.HasSuffix(trimmed, "|| true") {
			t.Errorf("this assignment dies under pipefail when its grep matches nothing, "+
				"skipping the empty-case branch below it:\n  %s", trimmed)
		}
	}
}

// The rollback unit, and the reason it is worth a guard: it is invisible until
// the moment it is needed. Nothing pulls :<sha> during normal operation, so if
// this arm stopped minting one, every build would stay green and every image
// would be valid — and the absence would surface only during an incident, as
// "there is nothing to roll back to."
//
// Rules 145 and 147: main push → :latest + :<sha>.
func TestMainChannel_PublishesLatestAndTheRollbackUnit(t *testing.T) {
	_, _, arm := imageTagArms(t, releaseYAML(t))

	if !strings.Contains(arm, "${IMAGE}:latest") {
		t.Errorf("main arm does not move :latest — production would stop tracking main's tip\n%s", arm)
	}
	if !strings.Contains(arm, "${IMAGE}:${GITHUB_SHA}") {
		t.Errorf("main arm publishes no commit-addressable image; there is no rollback target for production commits\n%s", arm)
	}
	// Rule 147: :latest tracks main's tip, and a second name for the same
	// image sends readers looking for a distinction that does not exist.
	if strings.Contains(arm, "${IMAGE}:main") {
		t.Errorf("main arm publishes :main — rule 147 says that tag should not exist\n%s", arm)
	}
}

// A release refreshes the CHANNEL and mints nothing else (rules 145 + 146).
//
// The specific regression: re-adding :<sha> here. The tag build rebuilds the
// SAME SOURCE as main's build minutes earlier, differing only in which APK is
// baked in — so a :<sha> minted here would overwrite main's immutable rollback
// target with different contents, under the same name. That is the exact thing
// rule 145's immutability clause exists to prevent, and it is the half with
// the incidents behind it.
func TestReleaseBuild_RefreshesTheChannelAndMintsNothingElse(t *testing.T) {
	arm, _, _ := imageTagArms(t, releaseYAML(t))

	if !strings.Contains(arm, "${IMAGE}:latest") {
		t.Errorf("tag arm does not refresh :latest — the channel would keep serving the PREVIOUS release's APK until someone pushed to main\n%s", arm)
	}
	if strings.Contains(arm, "GITHUB_SHA") {
		t.Errorf("tag arm mints a :<sha> image; that would re-push main's immutable rollback target with different bundled contents\n%s", arm)
	}
}

// No version-numbered image tags anywhere, on any arm (rule 145, and the
// operator's 2026-09-10 decision to drop them across every project).
//
// Asserted across the whole step rather than per-arm because the mistake this
// catches is re-adding one ANYWHERE, and the tag arm is only the likeliest
// spot. `${VERSION}` still legitimately appears in the step as the build's
// self-reported version, so the assertion has to name the image-tag form
// specifically rather than the variable — otherwise it would fire on correct
// code and get "fixed" by deleting the guard.
func TestNoVersionNumberedImageTags(t *testing.T) {
	yaml := releaseYAML(t)
	tagArm, devArm, mainArm := imageTagArms(t, yaml)

	for _, tc := range []struct{ name, arm string }{
		{"tag", tagArm}, {"dev", devArm}, {"main", mainArm},
	} {
		for _, forbidden := range []string{
			"${IMAGE}:${VERSION}",
			"${IMAGE}:v",
			"${IMAGE}:${GITHUB_REF#refs/tags/}",
		} {
			if strings.Contains(tc.arm, forbidden) {
				t.Errorf("%s arm publishes a version-numbered image tag (%q); git and the build's self-reported version answer \"which build is this\"\n%s",
					tc.name, forbidden, tc.arm)
			}
		}
	}
}

// The verify job asserted the :<version> image existed. With version tags
// gone that assertion would fail every release for a tag nothing mints — so
// this pins that it was re-pointed rather than deleted, since deleting it is
// the tempting way to make a failing guard go green.
func TestVerifyJob_ChecksTheRollbackImageNotAVersionTag(t *testing.T) {
	yaml := releaseYAML(t)

	if !strings.Contains(yaml, "- name: Rollback image must exist for the tagged commit") {
		t.Fatal("the release-verification step that checks an image exists is gone; an image push that silently did not happen would now pass verification")
	}
	step := stepBody(t, yaml, "Rollback image must exist for the tagged commit")
	if !strings.Contains(step, "${IMAGE}:${GITHUB_SHA}") {
		t.Errorf("the verify step does not inspect the commit's rollback image\n%s", step)
	}
	if strings.Contains(step, "${IMAGE}:${TAG}") {
		t.Errorf("the verify step still inspects a version-numbered image, which is no longer published — this would fail every release\n%s", step)
	}
}

// The server's self-reported version is now the ONLY thing that identifies a
// build, so a lane that stamps a channel word instead of a version silently
// removes that ability. It used to stamp the literal "main"/"dev".
func TestImageBuild_StampsADerivedVersionAndAChannel(t *testing.T) {
	yaml := releaseYAML(t)

	step := stepBody(t, yaml, "Build and push")
	for _, want := range []string{
		"MINSTREL_VERSION=",
		"MINSTREL_CHANNEL=",
	} {
		if !strings.Contains(step, want) {
			t.Errorf("Build and push does not pass %s — the image cannot report which build it is\n%s", want, step)
		}
	}

	// The version must come from the shared derivation, not from the ref.
	// Reading it off GITHUB_REF is what produced "main" and "dev" as version
	// strings, which is the regression this pins.
	_, _, mainArm := imageTagArms(t, yaml)
	if strings.Contains(mainArm, `version=main`) {
		t.Errorf("the main arm stamps the literal string \"main\" as a version; two images months apart would be indistinguishable\n%s", mainArm)
	}
	if !strings.Contains(yaml, "ci/version.sh HEAD | sed") {
		t.Error("the image job no longer derives its version from ci/version.sh — the version and the APK's version can now drift apart")
	}
}