package buscompose

import (
	"fmt"
	"slices"
	"strings"

	"git.novox.be/novox/mesh-sdk/go/delivery"
)

// The writers table (novox/hq to-be 45 §1, ADR 0227 rule 1), compiled in.
//
// **Every kind of state the core keeps has one writer; anyone else asks it.** The table is the design's,
// row for row, with what each row writes on the bus where it writes there. Two things read it: the
// composition of every principal's grants (PermissionsFor), which **refuses a grant that lets a
// principal publish on a subject another writes** — so a second writer cannot be granted by accident,
// and the composition says which state and whose — and the test beside it, which walks the rows
// against the design's list and the composition of a whole mesh. Changing a writer is a change to
// this table, through a decision.

// WriterRow is one row of the writers table.
type WriterRow struct {
	State  string
	Writer string
	KeptIn string
	Others string
	// Subjects are the bus subjects a write of this state is a publish to; none for state kept off the
	// bus (a module's own store) or not built yet.
	Subjects []string
	// Writes says a principal granted a publish pattern overlapping Subjects is this state's writer —
	// given the pattern, because a machine writes its own report and no other's.
	Writes func(p Principal, pattern string) bool
	// Shared says why more than one principal may publish here; empty for one writer.
	Shared string
}

// createsDeclared, and the other writers' tests, are who a row's writer is as a principal.
//
// createsDeclared is the grants part creating one stream a manifest declares, by its own name: the create alone, never an
// update or a delete (novox/hq ADR 0547 §5; the operator, 2026-10-26 08:54); or the bus module's tools deleting one of
// the ended controller's leftover streams (ADR 0590 clause 6).
func createsDeclared(p Principal, pattern string) bool {
	if removesLeftover(p, pattern) {
		return true
	}
	name, ok := strings.CutPrefix(pattern, "$JS.API.STREAM.CREATE.")
	if ok && p.Kind == KindModule && p.Module == GrantsModule && name == GrantsUserListObjectStream {
		return true
	}
	return ok && p.Kind == KindModule && p.Module == GrantsModule && slices.Contains(p.CreatesStreams, name) &&
		safeSubject.MatchString(name)
}

// ownMachine is a node writing a subject whose third token is its own name, and no wildcard there.
func ownMachine(p Principal, pattern string) bool {
	tokens := strings.Split(pattern, ".")
	return p.Kind == KindNode && len(tokens) > 2 && tokens[2] == p.Node
}

// holdsSeatOf is a principal holding the seat a `mesh.seat.<seat>.…` pattern names: its module's own
// principal, or the node tools carrying a module that holds it (ADR 0175, the runtime is its modules).
func holdsSeatOf(p Principal, pattern string) bool {
	tokens := strings.Split(pattern, ".")
	if len(tokens) < 3 {
		return false
	}
	seat := tokens[2]
	holds := func(seats []Seat) bool {
		return slices.ContainsFunc(seats, func(s Seat) bool { return s.Name == seat })
	}
	switch p.Kind {
	case KindModule:
		return holds(p.Holds)
	case KindNodeTools:
		return slices.ContainsFunc(p.Carries, func(d Declared) bool { return holds(d.Holds) })
	}
	return false
}

// ownModule is a module publishing under its own name, or the node tools carrying it.
func ownModule(p Principal, pattern string) bool {
	tokens := strings.Split(pattern, ".")
	if len(tokens) < 3 {
		return false
	}
	module := tokens[2]
	switch p.Kind {
	case KindModule:
		return p.Module == module
	case KindNodeTools:
		return slices.ContainsFunc(p.Carries, func(d Declared) bool { return d.Module == module })
	}
	return false
}

// moduleNamed is the writer that is module: its own principal, a process of it, or the node tools carrying it.
func moduleNamed(module string) func(Principal, string) bool {
	return func(p Principal, _ string) bool {
		switch p.Kind {
		case KindModule, KindProcess:
			return p.Module == module
		case KindNodeTools:
			return slices.ContainsFunc(p.Carries, func(d Declared) bool { return d.Module == module })
		}
		return false
	}
}

// ownAnnouncer is a module, a process of it or the node tools carrying it saying what that module keeps (novox/hq ADR
// 0495 clause 2): each under its own name alone.
func ownAnnouncer(p Principal, pattern string) bool {
	tokens := strings.Split(pattern, ".")
	if len(tokens) < 3 {
		return false
	}
	if p.Kind == KindProcess {
		return p.Module == tokens[2]
	}
	return ownModule(p, pattern)
}

// ownProvisioner is a machine's provisioner client saying a report about its own machine: the third token of
// `prov.applied.<node>.…` is its machine (novox/hq ADR 0349 §4, design 57 P3).
func ownProvisioner(p Principal, pattern string) bool {
	tokens := strings.Split(pattern, ".")
	return p.Kind == KindProvisioner && len(tokens) > 3 && tokens[2] == p.Node
}

// ownNodeKeys is a node writing the have keys of its own node: `$KV.<bucket>.<node>.…`, the node in the third token
// and no wildcard there (novox/hq ADR 0429 §1).
func ownNodeKeys(p Principal, pattern string) bool {
	tokens := strings.Split(pattern, ".")
	return p.Kind == KindNode && len(tokens) > 2 && tokens[2] == p.Node
}

// kvOf is a bucket's write subjects.
func kvOf(bucket string) []string { return []string{"$KV." + bucket + ".>"} }

// WritersTable is to-be 45 §1, in its order.
var WritersTable = []WriterRow{
	{State: "a machine's applied state and its report", Writer: "the node-engine's apply queue",
		KeptIn: "the machine; the report on the bus", Others: "the reconcile and a delivery enqueue, never apply",
		// And its health statement between reports (novox/hq ADR 0240): the same writer stating the same
		// machine, inside the grant it already had (`mesh.control.<its own>.>`). And a line mesh-cli was given
		// on the machine (novox/hq ADR 0272): that subject is this machine's engine's alone.
		Subjects: []string{"mesh.control.*.report", "mesh.control.*.health", "mesh.control.*.cli"}, Writes: ownMachine},
	{State: "stream definitions and bus permissions", Writer: "the grants part", KeptIn: "the bus", Others: "—",
		// A stream's definition, and a durable consumer's by the API that names it so. Not every
		// consumer create: a module watching its own bucket makes and deletes an ordered consumer on the
		// bucket's stream (ADR 0201), which defines nothing the mesh keeps.
		Subjects: []string{"$JS.API.STREAM.CREATE.>", "$JS.API.STREAM.UPDATE.>", "$JS.API.STREAM.DELETE.>",
			"$JS.API.CONSUMER.DURABLE.CREATE.>"},
		Writes: createsDeclared,
		Shared: "the grants part creates a stream a manifest declares, by its name, and never updates or deletes one (novox/hq ADR 0547 §5; the operator, 2026-10-26 08:54); the bus module's tools account deletes the ended controller's leftover streams, each by its name, and no other (novox/hq ADR 0590 clause 6)"},
	{State: "builds and their outcomes", Writer: "the build seat's holder", KeptIn: "its own state",
		Others:   "the builder asks",
		Subjects: []string{"mesh.seat.node-build-agent.event.built", "mesh.seat.mesh-build-machine.event.built"},
		Writes:   holdsSeatOf,
		Shared:   "every machine holding the build seat answers the asks it took; each outcome names its ask"},
	// What a module keeps and who may read it (novox/hq ADR 0495 clauses 2 and 3, issue 1790): said by the module.
	{State: "a module's states announced", Writer: "the module itself, from its code, under its own name",
		KeptIn: "the bus (EVENTS)", Others: "the grants part grants readers from it",
		Subjects: []string{"mesh.mod.*.event.states"}, Writes: ownAnnouncer},
	{State: "a merge announced", Writer: "one announcer per forge (the hook, or the poll when the hook is absent — never both)",
		KeptIn: "the bus", Others: "—", Subjects: []string{"mesh.mod.*.event.pull.merged"}, Writes: ownModule},
	// A pull request's head, before it merges (novox/hq to-be 45 §9): the same one announcer.
	{State: "a pull request's head announced", Writer: "the forge's announcer, the one that announces its merges",
		KeptIn: "the bus", Others: "the checker checks it", Subjects: []string{"mesh.mod.*.event.pull.updated"},
		Writes: ownModule},
	{State: "a pull request's merge check", Writer: "the checker that ran it",
		KeptIn: "the bus", Others: "the forge's holder sets it as the pull request's status"},
	{State: "a provider's standing", Writer: "the provider", KeptIn: "the provider's events",
		Others: "the watchman keeps the newest word as a condition",
		Subjects: []string{"mesh.mod.*.event.provisioner.failing", "mesh.mod.*.event.provisioner.recovered",
			"mesh.mod.*.event.provisioner.retirement"},
		Writes: ownModule},
	{State: "the operator-channel's open messages", Writer: "the seat's holder", KeptIn: "its own key-value state",
		Others: "—"},
	// The seat mesh-enrolment's open enrolments (novox/hq ADR 0587 §2, issue 774): its holder alone writes them, each a
	// compare-and-set at the revision read; the grants part reads them as a named reader.
	{State: "the open enrolments", Writer: "the seat mesh-enrolment's holder, compare-and-set",
		KeptIn:   "key-value " + delivery.EnrolmentsBucket + ", with per-key expiry",
		Others:   "the grants part reads them (a named reader) and composes each enrol.<node> user from them",
		Subjects: kvOf(delivery.EnrolmentsBucket), Writes: moduleNamed(delivery.EnrolmentModule)},
	// Which login each node uses (novox/hq ADR 0583 §1 insight): the vault alone writes it.
	{State: "a node's logins", Writer: "the vault", KeptIn: "key-value " + delivery.NodeLoginsBucket,
		Others:   "the grants part reads every key, each node's engine its own node's key alone",
		Subjects: kvOf(delivery.NodeLoginsBucket), Writes: moduleNamed(delivery.VaultModule)},
	// What a consumer gave up on (novox/hq issue 330): copied by the watchman from the server's notice (ADR 0564
	// clause 5, ADR 0590 clause 2).
	{State: "a message a consumer gave up on", Writer: "the watchman", KeptIn: "the bus, the stream " + DeadLettersStream,
		Others:   "read through the watchman's dead-letters; delivered again by nobody until the hand-act log's home is delivered",
		Subjects: []string{deadLetterPrefix + ">", againPrefix + ">"}, Writes: keepsDeadLetters},
	// What each machine has of each module (novox/hq ADR 0429 §1, design 47): written by that machine's node-engine under
	// its own node's keys; the view and the watchman read it.
	{State: "a machine's have", Writer: "the node-engine of the machine, under its own keys `<node>.>`",
		KeptIn: "key-value " + delivery.HaveBucket + ", twenty revisions of each key",
		Others: "read through `reads` as node-engine.have", Subjects: kvOf(delivery.HaveBucket), Writes: ownNodeKeys},
	// The acts a node's engine was asked through its node seat, and its own asks (novox/hq ADR 0563 §2, §3): the
	// node-engine's declared state, created by the grants part, written by each node's engine under its own keys.
	// A node's own health report (issue 774): its engine's own key, read by the watchman.
	{State: "a machine's health report", Writer: "the node-engine of the machine, its key `<node>` alone",
		KeptIn: "key-value " + delivery.NodeHealthBucket, Others: "read by the watchman through `reads`",
		Subjects: kvOf(delivery.NodeHealthBucket), Writes: ownNodeKeys},
	// A node's declared packages (novox/hq ADR 0565 clause 6): its engine's own key, read by pacman's verbs.
	{State: "a machine's declared packages", Writer: "the node-engine of the machine, its key `<node>` alone",
		KeptIn: "key-value " + EnginePackagesBucket, Others: "read by pacman through `reads`",
		Subjects: kvOf(EnginePackagesBucket), Writes: ownNodeKeys},
	// A node's placed modules' data items (novox/hq ADR 0577 clause 1): its engine's own keys, read by that node's disk-load.
	{State: "a machine's data items", Writer: "the node-engine of the machine, under its own keys `<node>.>`",
		KeptIn: "key-value " + EngineDataBucket, Others: "read by the node's disk-load through `reads`, its own node's keys alone",
		Subjects: kvOf(EngineDataBucket), Writes: ownNodeKeys},
	{State: "a machine's hand acts", Writer: "the node-engine of the machine, under its own keys `<node>.>`, compare-and-set",
		KeptIn: "key-value " + EngineActsBucket + ", the node-engine's declared state acts",
		Others: "read through the node seat's verb acts", Subjects: kvOf(EngineActsBucket),
		Writes: func(p Principal, pattern string) bool {
			return ownNodeKeys(p, pattern) || removesEngineActs(p, pattern)
		},
		Shared: "the bus module's tools account removes keys of a full bucket, for removal only (novox/hq ADR 0564 Limits 4)"},
	// The object buckets (novox/hq ADR 0486 §2, ADR 0547 clause 7): the declaration files' buckets the ended controller
	// wrote are written by nobody (ADR 0590); the grants part writes its own.
	{State: "an object bucket", Writer: "the grants part, its own bucket alone",
		KeptIn: "the object bucket " + DeclarationFilesBucket + "-<node> of each node, an object removed a day after the " +
			"node's latest declaration no longer names it",
		Others:   "a node-engine reads an object of its own bucket by its name and may neither list the bucket nor write it",
		Subjects: []string{"$O.*.>"}, Writes: func(p Principal, pattern string) bool {
			return grantsOwnObjects(p, pattern)
		},
		Shared: "nobody else: the grants part writes its own object bucket " + GrantsUserListObjects + ", the user list sealed to the bus node, and no other (novox/hq ADR 0547 clause 7)"},
	// What a machine's provisioner client placed of a module's files (novox/hq ADR 0349 §4, design 57 P6): its own
	// machine's word alone, which a walk's end and a gate wait for (ADR 0362, ADR 0349 §15). Kept newest per module
	// in the stream ProvAppliedStream, and by the client in the provisioner server's `applied` bucket.
	{State: "a module's files placed on a machine", Writer: "that machine's provisioner client",
		KeptIn: "the bus, the stream " + ProvAppliedStream + ", newest per module; and key-value " +
			ProvisionerAppliedBucket,
		Others:   "the watchman reads it; a failure is that machine's failed apply",
		Subjects: []string{"prov.applied.*.>"}, Writes: ownProvisioner},
}

// CheckWriters refuses a grant that lets a principal publish on a subject the writers table gives
// another writer (to-be 45 §1): which state, whose, and the pattern that would make a second writer.
func CheckWriters(p Principal, publish []string) error {
	var problems []string
	for _, pattern := range publish {
		for _, row := range WritersTable {
			if row.Writes == nil {
				continue
			}
			for _, subject := range row.Subjects {
				if !SubjectsOverlap(pattern, subject) || row.Writes(p, pattern) {
					continue
				}
				problems = append(problems, fmt.Sprintf("%s may publish %s, which writes %s (%s), whose writer is %s",
					p.Username(), pattern, row.State, subject, row.Writer))
			}
		}
	}
	if len(problems) == 0 {
		return nil
	}
	return fmt.Errorf("a second writer would be granted (novox/hq to-be 45 §1, one writer per piece of state):\n  %s",
		strings.Join(problems, "\n  "))
}

// SubjectsOverlap says some subject matches both patterns: `*` is one token, `>` one or more to the end.
func SubjectsOverlap(a, b string) bool {
	x, y := strings.Split(a, "."), strings.Split(b, ".")
	for i := 0; ; i++ {
		switch {
		case i == len(x) && i == len(y):
			return true
		case i == len(x) || i == len(y):
			return false
		case x[i] == ">" || y[i] == ">":
			return true
		case x[i] == "*" || y[i] == "*" || x[i] == y[i]:
			continue
		default:
			return false
		}
	}
}