package catalogue

import (
	"fmt"
	"regexp"
	"sort"
	"strings"
)

// Seats a module declares of its own (novox/hq ADR 0118).
//
// The set of seats a mesh has is **derived**: the mesh's own, in seats.go, plus those declared by
// every module it has registered. Still closed — a seat named nowhere is refused — but computed
// from the catalogue rather than written in the controller, which is what ADR 0110 actually
// needed and a hand-maintained table could not keep. Its own evidence: the enumeration done by
// hand while that record was written reported eleven claims where there were thirteen.
//
// **What can be checked from one manifest and what cannot.** A declaration's shape, its scope,
// and the reserved prefix are facts about the manifest in front of you. Whether a seat anybody
// names actually exists, whether two modules declared the same one, and whether a holder
// satisfies the protocol are facts about the *catalogue* — so they are checked at registration,
// by CatalogueProblems, which is the last moment the mesh can still say no.

// meshSeatPrefix is reserved to the mesh. The prefix *is* the reservation rule: no list of
// reserved names to maintain, no way for the mesh's own namespace to be colonised by a manifest,
// and nothing to keep in step when a mesh seat is added.
const meshSeatPrefix = "mesh-"

// retiredLoginShell is the one name outside the prefix a module may not declare: the login shell's,
// from when a module declared it (novox/hq ADR 0176), before it became the mesh's (ADR 0204).
const retiredLoginShell = "login-shell"

// A SeatDeclaration is a role a module offers on the bus: what may be sent to it, what it says,
// and what it answers. A caller declares that it uses the *seat*, never the module, so the
// implementation can be replaced under it.
type SeatDeclaration struct {
	Name  string `json:"name"`
	Scope string `json:"scope,omitempty"`

	// Accepts are the verbs others may submit work on. Each becomes a work-queue subject, and
	// the holder is the only consumer — so exactly one worker does the job, by construction
	// rather than by how carefully somebody wrote a subscribe call.
	Accepts []string `json:"accepts,omitempty"`
	// Emits are the verbs the holder publishes: 1:many, nobody obliged to act.
	Emits []string `json:"emits,omitempty"`
	// Serves are the verbs the holder answers: request and reply, awaited. A bare name, or the
	// verb in full with its schema (novox/hq ADR 0132).
	Serves []Verb `json:"serves,omitempty"`

	// RetainSeconds is how long the inbound backlog survives with no holder, zero for the
	// mesh's default. Retention belongs to whoever owns the namespace (design 29 §3) — a seat
	// owns its own, which is why a seat is also the answer for a module that needs retention
	// its events cannot have.
	RetainSeconds int `json:"retain-seconds,omitempty"`

	// Kinded makes the seat a kinded bench (novox/hq ADR 0234 §2, ADR 0259 §3): its holders are different
	// modules, each claiming one kind, and each verb's subject carries the kind. Only the benches in
	// KindedBenches may be kinded; making another is a decision, recorded.
	Kinded bool `json:"kinded,omitempty"`
	// ByCaller are accepts and emits whose subject's last token names the calling module (ADR 0259 §3): a
	// user submits such an accept, and hears such an event, under its own name and no other.
	ByCaller []string `json:"by-caller,omitempty"`
	// Proofs are verbs carried as core request and reply, never on a stream: what travels on them (a code
	// the operator typed) is never kept (ADR 0259 §3). On a kinded bench a holder asks with its own kind and
	// the modules watching the seat answer.
	Proofs []string `json:"proofs,omitempty"`
	// Records are state buckets of the declaring module that each user reads under its own name — the
	// keys `<user>.…` and no other (ADR 0259 §3).
	Records []string `json:"records,omitempty"`
}

// KindedBenches are the seats that may be kinded (novox/hq ADR 0234 §2): `channel` sends to the operator,
// `intake` takes what the operator answers. Another is a decision, recorded, as ADR 0223 asks of a bench.
var KindedBenches = map[string]bool{"channel": true, "intake": true}

// NamedByCaller says whether one of the seat's verbs is named by its caller.
func (s SeatDeclaration) NamedByCaller(verb string) bool {
	for _, v := range s.ByCaller {
		if v == verb {
			return true
		}
	}
	return false
}

// At is this declaration's scope, with the default applied. Mesh by default, because a seat
// declared by a module is nearly always "there is one of these in the mesh" — a per-node worker
// is the deliberate case, and says so.
func (s SeatDeclaration) At() string {
	if s.Scope == "" {
		return ScopeMesh
	}
	return s.Scope
}

// verbs is everything the protocol names, for the checks that do not care which half.
func (s SeatDeclaration) verbs() []string {
	out := append([]string{}, s.Accepts...)
	out = append(out, s.Emits...)
	return append(out, VerbNames(s.Serves)...)
}

// declaredSeatProblems is what one manifest can be judged on alone.
func declaredSeatProblems(m Manifest) []string {
	var problems []string
	seen := map[string]bool{}

	for _, s := range m.DefinesSeats {
		switch {
		case s.Name == "":
			problems = append(problems, fmt.Sprintf("%s declares a seat with no name", m.Module))
			continue
		case !name.MatchString(s.Name):
			problems = append(problems, fmt.Sprintf(
				"%s declares a seat named %q, which is not a usable name", m.Module, s.Name))
			continue
		case strings.HasPrefix(s.Name, meshSeatPrefix):
			// The mesh's own code dereferences its seats by name — the resolver *is* the thing
			// that finds the store — so the prefix is not a convention, it is a namespace.
			problems = append(problems, fmt.Sprintf(
				"%s declares a seat named %q; %q is reserved to the mesh, which defines its own "+
					"seats (novox/hq ADR 0118)", m.Module, s.Name, meshSeatPrefix+"*"))
			continue
		}
		if s.Name == retiredLoginShell {
			// The name ADR 0176 gave the login shell when the zsh module declared it. The seat is
			// the mesh's now, so a module declaring the old name would be a second login shell
			// beside it, with a protocol of its own (novox/hq ADR 0204).
			problems = append(problems, fmt.Sprintf(
				"%s declares a seat named %q; the login shell is the mesh's own seat %s, which a shell "+
					"module claims and none declares (novox/hq ADR 0204)", m.Module, s.Name, LoginShellSeat))
			continue
		}
		if seen[s.Name] {
			problems = append(problems, fmt.Sprintf(
				"%s declares the seat %q twice", m.Module, s.Name))
			continue
		}
		seen[s.Name] = true

		if _, isMesh := SeatNamed(s.Name); isMesh {
			problems = append(problems, fmt.Sprintf(
				"%s declares %q, which is a seat the mesh already defines", m.Module, s.Name))
		}
		switch s.At() {
		case ScopeNode, ScopeSite, ScopeMesh:
		default:
			problems = append(problems, fmt.Sprintf(
				"%s declares seat %s at scope %q; a seat is held per node, per site or per mesh",
				m.Module, s.Name, s.Scope))
		}
		// A seat with an empty protocol is allowed, and is the mesh saying what a machine is:
		// which module is this node's packet filter, or its showcase. Design 26 calls it a seat
		// that delivers nothing, and that is most of the node-scoped ones. ADR 0126's "a declared
		// seat carries a protocol" governs what a holder must satisfy, not that every seat offers
		// something — a marker seat's protocol is satisfied by holding it. Nothing can reach this
		// state by accident: a mistyped field name is refused by the parser above, so an empty
		// protocol was written as one.
		for _, v := range s.verbs() {
			if !name.MatchString(v) {
				problems = append(problems, fmt.Sprintf(
					"%s declares %s.%s, which is not a usable verb", m.Module, s.Name, v))
			}
		}
		problems = append(problems, trafficProblems(m, s)...)
	}

	for _, u := range m.Uses {
		if !name.MatchString(u) {
			problems = append(problems, fmt.Sprintf("%s uses %q, which is not a usable seat name", m.Module, u))
		}
	}
	return problems
}

// trafficProblems is what one declaration of the rules of ADR 0259 §3 can be judged on alone.
func trafficProblems(m Manifest, s SeatDeclaration) []string {
	var problems []string
	if s.Kinded && !KindedBenches[s.Name] {
		problems = append(problems, fmt.Sprintf(
			"%s declares %s as a kinded bench; only channel and intake are kinded, and another is a "+
				"decision, recorded (novox/hq ADR 0234)", m.Module, s.Name))
	}
	if s.Kinded && len(s.ByCaller) > 0 {
		problems = append(problems, fmt.Sprintf(
			"%s declares %s kinded and names verbs by their caller; a kinded bench's subjects carry the kind",
			m.Module, s.Name))
	}
	for _, v := range s.ByCaller {
		inAccepts, inEmits := false, false
		for _, a := range s.Accepts {
			inAccepts = inAccepts || a == v
		}
		for _, e := range s.Emits {
			inEmits = inEmits || e == v
		}
		if !inAccepts && !inEmits {
			problems = append(problems, fmt.Sprintf(
				"%s names %s.%s by its caller, which the seat neither accepts nor emits", m.Module, s.Name, v))
		}
	}
	for _, v := range s.Proofs {
		if !name.MatchString(v) || strings.Contains(v, ".") {
			problems = append(problems, fmt.Sprintf("%s declares the proof %s.%s, which is not a usable verb",
				m.Module, s.Name, v))
		}
	}
	if len(s.Proofs) > 0 && !s.Kinded {
		problems = append(problems, fmt.Sprintf(
			"%s declares proofs on %s, which is not kinded; a proof is asked by a holder of a kind",
			m.Module, s.Name))
	}
	for _, r := range s.Records {
		kept := false
		for _, st := range m.State {
			kept = kept || st.Name == r
		}
		if !kept {
			problems = append(problems, fmt.Sprintf(
				"%s says %s's users read its records %q, which it keeps no state of", m.Module, s.Name, r))
		}
	}
	return problems
}

// A Shelf is every manifest the mesh has registered, by module name.
type Shelf map[string]Manifest

// CatalogueProblems are the rules no single manifest can be judged against.
//
// Run at registration, which is the last moment the mesh can still refuse: after it, a caller is
// bound to a seat and a refusal is an outage rather than a conversation.
func CatalogueProblems(shelf Shelf) []string {
	var problems []string

	// Who declares what, and who declared it first.
	declaredBy := map[string]string{}
	declared := map[string]SeatDeclaration{}
	for _, module := range shelfOrder(shelf) {
		for _, s := range shelf[module].DefinesSeats {
			if s.Name == "" {
				continue
			}
			if first, taken := declaredBy[s.Name]; taken {
				// The second loses. A seat name meaning two different protocols is the failure
				// nobody could diagnose afterwards — a caller would bind to whichever happened
				// to register first, and the symptom would appear in the other module.
				problems = append(problems, fmt.Sprintf(
					"%s declares the seat %q, which %s already declares; a seat name means one "+
						"protocol", module, s.Name, first))
				continue
			}
			declaredBy[s.Name] = module
			declared[s.Name] = s
		}
	}

	exists := func(seat string) bool {
		if _, isMesh := SeatNamed(seat); isMesh {
			return true
		}
		_, ok := declaredBy[seat]
		return ok
	}

	// Who claims each kind of a kinded bench, so a second claim of one kind is refused (ADR 0234 §2).
	kindsTaken := map[string]string{}

	for _, module := range shelfOrder(shelf) {
		m := shelf[module]
		for _, c := range m.Claims {
			if c.Kind != "" {
				if _, isModuleSeat := declared[c.Name]; !isModuleSeat {
					problems = append(problems, fmt.Sprintf(
						"%s claims %s of kind %q, and only a kinded bench takes a kind", module, c.Name, c.Kind))
				}
			}
		}

		// A `uses` naming nothing is where ADR 0110's guarantee lands under a derived set: the
		// same refusal, at the same moment, from a set nobody maintains by hand.
		for _, u := range m.Uses {
			if !exists(u) {
				problems = append(problems, fmt.Sprintf(
					"%s uses the seat %q, which no module declares and the mesh does not define",
					module, u))
			}
		}

		for _, c := range m.Claims {
			if !exists(c.Name) {
				problems = append(problems, fmt.Sprintf(
					"%s claims the seat %q, which no module declares and the mesh does not define",
					module, c.Name))
				continue
			}
			s, isModuleSeat := declared[c.Name]
			if !isModuleSeat {
				// **A mesh seat is judged here and nowhere else** (novox/hq ADR 0122): the set is
				// the store's, and this is the only place that runs with the store's set loaded.
				// The parser cannot do it — it also runs on the build machine, against whatever
				// set that binary was compiled with.
				seat, _ := SeatNamed(c.Name)
				if err := CanHold(m, seat); err != nil {
					problems = append(problems, err.Error())
				}
				continue
			}
			problems = append(problems, kindProblems(module, c, s, kindsTaken)...)
			if c.At() != s.At() {
				problems = append(problems, fmt.Sprintf(
					"%s claims %s at scope %q, and %s declares it at %s",
					module, c.Name, c.At(), declaredBy[c.Name], s.At()))
			}
			// A holder that does not answer what the seat promises is a caller's timeout, found
			// at assignment instead.
			if missing := unserved(m, c, s); len(missing) > 0 {
				problems = append(problems, fmt.Sprintf(
					"%s claims %s but does not serve %s, which that seat's protocol promises",
					module, c.Name, strings.Join(missing, ", ")))
			}
		}
	}
	// A read of a module's state that module does not keep (novox/hq ADR 0201) — said only where the
	// owner is on the shelf, as a consumer may be installed before its emitter.
	var manifests []Manifest
	for _, module := range shelfOrder(shelf) {
		manifests = append(manifests, shelf[module])
	}
	problems = append(problems, StateReadsNothingDeclares(manifests)...)
	sort.Strings(problems)
	return problems
}

// ChannelCapabilities is the fixed vocabulary `channel-capabilities/1` (novox/hq ADR 0234 §2): a word
// outside it is refused. `max-length:<N>` takes a number.
var ChannelCapabilities = map[string]bool{
	"deliver": true, "reaches-away": true, "loud": true, "silent": true, "edit": true,
	"reaches-when-mesh-down": true, "private": true,
	"choice": true, "reply": true, "threads": true, "operator-first": true,
	"verified-sender": true, "exact-render": true, "code-factor": true, "key-factor": true,
}

var maxLength = regexp.MustCompile(`^max-length:[1-9][0-9]{0,6}$`)

// capabilityProblems are the words of a claim outside the vocabulary, and capabilities on a claim of a
// seat that is not kinded.
func capabilityProblems(module string, c Claim, kinded bool) []string {
	if len(c.Capabilities) == 0 {
		return nil
	}
	if !kinded {
		return []string{fmt.Sprintf("%s claims %s with capabilities, and only a kinded bench's claim carries them",
			module, c.Name)}
	}
	var problems []string
	for _, w := range c.Capabilities {
		if !ChannelCapabilities[w] && !maxLength.MatchString(w) {
			problems = append(problems, fmt.Sprintf(
				"%s claims %s with the capability %q, which channel-capabilities/1 does not have", module, c.Name, w))
		}
	}
	return problems
}

// kindProblems is a claim judged against a declared seat's kind: a kinded bench takes one claim per kind,
// a usable name; any other seat takes none.
func kindProblems(module string, c Claim, s SeatDeclaration, taken map[string]string) []string {
	if problems := capabilityProblems(module, c, s.Kinded); len(problems) > 0 {
		return problems
	}
	switch {
	case !s.Kinded && c.Kind != "":
		return []string{fmt.Sprintf("%s claims %s of kind %q, and only a kinded bench takes a kind",
			module, c.Name, c.Kind)}
	case !s.Kinded:
		return nil
	case c.Kind == "":
		return []string{fmt.Sprintf("%s claims the kinded bench %s and names no kind", module, c.Name)}
	case !name.MatchString(c.Kind) || strings.Contains(c.Kind, "."):
		return []string{fmt.Sprintf("%s claims %s of kind %q, which is not a usable name", module, c.Name, c.Kind)}
	}
	key := c.Name + "/" + c.Kind
	if first, ok := taken[key]; ok && first != module {
		return []string{fmt.Sprintf("%s claims %s of kind %q, which %s already claims; a kind has one holder",
			module, c.Name, c.Kind, first)}
	}
	taken[key] = module
	return nil
}

// unserved is what a seat's protocol promises and the claimant does not answer. Only the tools
// are checked: `accepts` and `emits` are wired by the runtime from the declaration, while a tool
// is code the module either has or has not written — under the claim's serves, or among its own.
func unserved(m Manifest, c Claim, s SeatDeclaration) []string {
	has := map[string]bool{}
	for _, t := range c.ServesFor(m) {
		has[t] = true
	}
	var missing []string
	for _, t := range s.Serves {
		if !has[t.Name] {
			missing = append(missing, t.Name)
		}
	}
	return missing
}

// shelfOrder is the catalogue in a stable order, so two runs report the same problems in the same
// sequence — a refusal that reorders itself is a refusal nobody can diff.
func shelfOrder(shelf Shelf) []string {
	out := make([]string, 0, len(shelf))
	for k := range shelf {
		out = append(out, k)
	}
	sort.Strings(out)
	return out
}