package stacks

import (
	"strings"

	"gitea.dooplex.hu/admin/felhom-controller/internal/util"
)

// ── Is this app behind the catalog, level with it, or AHEAD of it? (R-524, v0.260.0) ─────────────
//
// Slice 2 (v0.233.0) asked only "does the installed reference DIFFER from the catalog's?" and called
// every difference „Frissítés elérhető". MEASURED 2026-09-15 (BIGNIGHT Phase 6): privatebin was
// updated 2.0.5 → 2.0.6 and the catalog was then reverted to 2.0.5. The box read
// „Frissítés elérhető — ma", and the guarded Update behind that badge would have advanced the pin
// 2.0.6 → 2.0.5 — a DOWNGRADE offered to a household as an update, with a migrated datadir behind it
// and §4's ruling saying it cannot be undone.
//
// So the comparison gains a fourth answer. It lives HERE, in stacks, and not in web, because two
// callers must reach the SAME verdict: the badge (web.compareInstalledToTemplate) and the guarded
// update's refusal (Manager.UpdatePreflight). A comparison implemented twice is a comparison that
// drifts — the same lesson localisation learned when the badge's two language paths were written
// apart (R-589).
//
// IT QUERIES NO REGISTRY, exactly as before (09-update-architecture.md §8.1). Ordering is decided
// from the TAG TEXT alone, and only when the tag text can carry an order at all.

// UpdateOrder is the four-way answer to "how does what this app RUNS stand against what the catalog
// OFFERS?".
//
// ABSENT STILL MEANS UNKNOWN, AND NEVER „NAPRAKÉSZ" — the R-166 property slice 2 was built around,
// carried over verbatim. The new value is Ahead, and it is deliberately NOT folded into Current:
// the badge shows the same word for both, but the UPDATE must refuse only one of them, and a caller
// that cannot tell them apart cannot refuse correctly.
type UpdateOrder int

const (
	UpdateOrderUnknown UpdateOrder = iota // nothing recorded, or nothing to compare against
	UpdateOrderCurrent                    // every service runs exactly what the catalog pins
	UpdateOrderBehind                     // at least one service differs and is not provably newer
	UpdateOrderAhead                      // every differing service is provably NEWER than the catalog
)

// CatalogOrder compares an app's recorded installed images against what the catalog offers.
//
// The Ahead arm is deliberately the narrow one: EVERY differing service must be orderable and newer.
// One service that is older, or one tag that cannot carry an order, and the answer falls back to
// Behind — i.e. to exactly the behaviour of v0.233.0..v0.259.0. A half-ahead app is not a downgrade
// the box may refuse on its own; it is a mixed state a human should look at, and „Frissítés elérhető"
// is the honest label for it.
func CatalogOrder(s Stack) UpdateOrder {
	if !s.Deployed || s.Protected || s.Orphaned {
		// Not deployed: nothing is running. Protected: infra is ours, not the customer's to update.
		// Orphaned: the template is gone from the catalog, so there is nothing to be current WITH.
		return UpdateOrderUnknown
	}
	if s.AppConfig == nil || len(s.AppConfig.InstalledImages) == 0 {
		return UpdateOrderUnknown // legacy app.yaml — no record was ever written
	}
	if len(s.CatalogImages) == 0 {
		return UpdateOrderUnknown // no readable catalog template — cannot tell, so say nothing
	}
	if len(s.AppConfig.InstalledImages) != len(s.CatalogImages) {
		// A service was added or removed by the template. That IS a change the customer's running
		// stack has not taken up, and it is not a version order.
		return UpdateOrderBehind
	}
	differing := 0
	for svc, want := range s.CatalogImages {
		got, ok := s.AppConfig.InstalledImages[svc]
		if !ok {
			return UpdateOrderBehind // the catalog names a service the record does not cover
		}
		if got.Ref == want {
			continue
		}
		differing++
		if cmp, ok := CompareImageRefs(got.Ref, want); !ok || cmp <= 0 {
			return UpdateOrderBehind
		}
	}
	if differing == 0 {
		return UpdateOrderCurrent
	}
	return UpdateOrderAhead
}

// CompareImageRefs orders two image references the way a human reads them: -1 when a is older than
// b, 0 when they are the same version, 1 when a is newer. The second return is the whole point —
// FALSE means "these two cannot be ordered", and every caller must treat that as "do not know"
// rather than as "equal".
//
// It answers false, on purpose, for far more than it answers true:
//   - a digest-pinned reference (`…@sha256:…`) — the digest carries no order;
//   - a reference with no tag — the implicit `latest` is a moving target, not a position;
//   - two references to DIFFERENT images (`alpine:3.20` against `…/bookstack:26.05.2`) — the numbers
//     are comparable and the comparison is meaningless, which is the worst kind of false positive;
//   - any tag that is not plain digits and dots: `16-alpine`, `latest`, `26.05.2-ls310`, `stable`,
//     a date stamp, a git sha. 23 of the catalog's 66 pins float exactly like this (§8.1).
//
// THE ORDER ITSELF IS util.Version.Compare AND NOTHING ELSE. The house rule is one comparator in
// this repo; this function is a tag NORMALISER in front of it, never a second implementation.
func CompareImageRefs(a, b string) (int, bool) {
	repoA, tagA := splitImageRef(a)
	repoB, tagB := splitImageRef(b)
	if repoA == "" || repoA != repoB {
		return 0, false
	}
	va, sufA, okA := parseImageTag(tagA)
	vb, sufB, okB := parseImageTag(tagB)
	if !okA || !okB {
		return 0, false
	}
	// THE SUFFIXES MUST BE IDENTICAL, and this is not pedantry. `nextcloud:31.0.14-apache` and
	// `nextcloud:31.0.15-apache` are the same flavour of the same image and order cleanly; but
	// `26.05.2-ls310` against `26.05.2-ls311` differs only in a build number this function has no
	// rule for, and `…:2.4.0-alpine` against `…:2.4.0` is a different image content under one repo
	// name. Equal-or-nothing keeps every one of those out of the Ahead arm.
	if sufA != sufB {
		return 0, false
	}
	return va.Compare(vb), true
}

// splitImageRef separates `repo` from `tag`, and returns two empty strings whenever the reference
// carries no plain tag to compare.
//
// The `/` test after the last colon is what keeps a registry PORT from being read as a tag:
// `gitea.dooplex.hu:3000/admin/app` has a colon in it and no tag at all.
func splitImageRef(ref string) (repo, tag string) {
	if strings.Contains(ref, "@") {
		return "", "" // digest-pinned
	}
	i := strings.LastIndex(ref, ":")
	if i < 0 {
		return "", "" // no tag — the implicit `latest`
	}
	if strings.Contains(ref[i+1:], "/") {
		return "", "" // that colon was a registry port
	}
	return ref[:i], ref[i+1:]
}

// parseImageTag splits a tag into the version at its FRONT and whatever follows, and refuses
// anything whose front is not `X.Y` or `X.Y.Z` (an optional leading `v` is allowed).
//
//	"2.0.6"           → 2.0.6,  ""
//	"31.0.14-apache"  → 31.0.14, "-apache"     ← real: the catalog's nextcloud pin
//	"11.6"            → 11.6.0, ""             ← real: the catalog's mariadb pins
//	"16-alpine"       → refused: one component is not a version, it is a major line
//	"apache-2.57.0"   → refused: the version is not at the front (real: the catalog's kimai pin)
//	"20260915"        → refused: a date stamp is one component
//
// A two-part tag is padded with `.0` before it reaches the comparator. The padding is safe in the
// one direction that matters: it only ever adds the smallest possible patch number, and it is
// applied to whichever side is short, so it can never make an older tag look newer.
func parseImageTag(tag string) (util.Version, string, bool) {
	t := strings.TrimPrefix(tag, "v")
	end := 0
	for end < len(t) && ((t[end] >= '0' && t[end] <= '9') || t[end] == '.') {
		end++
	}
	head, suffix := t[:end], t[end:]
	parts := strings.Split(head, ".")
	if len(parts) < 2 || len(parts) > 3 {
		return util.Version{}, "", false
	}
	for _, p := range parts {
		if p == "" {
			return util.Version{}, "", false
		}
	}
	for len(parts) < 3 {
		parts = append(parts, "0")
	}
	v, err := util.ParseVersion(strings.Join(parts, "."))
	if err != nil {
		return util.Version{}, "", false
	}
	return v, suffix, true
}