package grants

import (
	"encoding/json"
	"errors"
	"fmt"
	"regexp"
	"slices"
	"strings"
	"time"

	"git.novox.be/novox/mesh-sdk/go/asks"
	"git.novox.be/novox/mesh-sdk/go/delivery"
	"mesh-grants/internal/buscompose"
)

// **The list the bus node loads** (novox/hq ADR 0547 clause 7, issue 1945). Each pass composes the bus's user list with
// the vault's hashes (the accounts block, buscompose.ComposeAccounts, as the bus module's file holds it), seals it to the
// bus node's key (the key the node says in its have of the bus module) and puts it as one object of the part's object
// bucket, named by its digest; then writes the key `user-list.sealed` naming it, with the revision, the user count and
// the users left out for want of a hash. The key always says FollowGrants: the bus node follows this list alone since the
// controller ended by its unassignment (ADR 0590, issue 1126). Only the process writes them (Objects); a tool asks it.

// KeySealed is the key of the state user-list the bus node reads (delivery.GrantsUserListKey).
const KeySealed = delivery.GrantsUserListKey

// Objects is the part's object bucket of sealed lists: the process's connection; nil in the tools.
type Objects interface {
	PutObject(name string, data []byte) error
	DeleteObject(name string) error
}

// ComposeList is the bus's user list as the file holds it, with each user's hash from the vault; the users left out
// for want of one; and the refused principals (refused, by user) the list carries with their grants kept from the list
// in force (kept), or leaves out where kept holds none (dropped, sorted). Pure.
func ComposeList(r buscompose.Records, hashes map[string]HeldHash, refused map[string]string, kept map[string]User) (list []byte, users int, leftOut, dropped []string, err error) {
	principals, err := buscompose.Users(r)
	if err != nil {
		return nil, 0, nil, nil, err
	}
	held := map[string]string{}
	for user, h := range hashes {
		held[user] = h.Hash
	}
	composing := slices.DeleteFunc(slices.Clone(principals), func(p buscompose.Principal) bool { _, no := refused[p.Username()]; return no })
	filled, missing := buscompose.WithPasswords(composing, held)
	text, err := buscompose.ComposeAccounts(filled)
	if err != nil {
		return nil, 0, nil, nil, err
	}
	var entries []string
	for _, user := range sortedKeys(refused) {
		u, ok := kept[user]
		switch {
		case !ok:
			dropped = append(dropped, user)
		case held[user] == "":
			missing = append(missing, user)
		default:
			entries = append(entries, keptEntry(u, held[user]))
		}
	}
	if text, err = withEntries(text, entries); err != nil {
		return nil, 0, nil, nil, err
	}
	slices.Sort(missing)
	return []byte(text), len(filled) + len(entries), missing, dropped, nil
}

// Sealed is the part's key `user-list.sealed` as written, and whether there is one.
func (p *Part) Sealed() (delivery.GrantsUserList, uint64, bool) {
	raw, rev, found, err := p.Store.Get(StateUserList, KeySealed)
	if err != nil || !found {
		return delivery.GrantsUserList{}, 0, false
	}
	g, err := delivery.DecodeGrantsUserList(raw)
	if err != nil {
		return delivery.GrantsUserList{}, 0, false
	}
	return g, rev, true
}

// writeSealed puts the list sealed to the bus node and writes the key, each only when what it says changed. It says in
// res what it wrote, or why it wrote nothing.
func (p *Part) writeSealed(res *Result, list []byte, users int, leftOut, dropped []string, in Inputs, bus []string, lost []string, composed []User) {
	cur, _, had := p.Sealed()
	next := cur
	// The bus node follows this list alone (ADR 0571 clause 8): always since the controller ended by its unassignment
	// (novox/hq ADR 0590, issue 1126).
	next.Follow = delivery.FollowGrants
	key := ""
	if in.Loaded != nil {
		key = in.Loaded.Key
	}
	digest := delivery.UserListDigest(list)
	why, held := "", ""
	switch {
	case p.Objects == nil:
		// The tools: the process writes.
		res.Sealed = sealedSays(cur, had, "")
		return
	case in.BusNode == "":
		why = "no node runs the bus's module, so the list is sealed to nobody"
	case key == "":
		why = "the bus node's have of the bus module names no key yet (its node-engine says it from this release)"
	case cur.Digest != digest && p.holdsBack(in, leftOut, dropped, bus, lost, digest) != "":
		// The list in force is never replaced by one composed past a failed read, or one that drops a user of it for want
		// of a hash: that user's module would be locked out of the bus (review of the switch).
		why = p.holdsBack(in, leftOut, dropped, bus, lost, digest)
		held = why
		p.keepHashHold(res, digest)
	case cur.Digest != digest || cur.SealedTo != delivery.SealingKeyID(key) || cur.Node != in.BusNode:
		object, err := delivery.SealUserList(list, key)
		if err == nil {
			err = p.Objects.PutObject(delivery.UserListObjectName(digest), object)
		}
		if err != nil {
			res.Errors = append(res.Errors, "the sealed user list could not be put: "+err.Error())
			res.Sealed = sealedSays(cur, had, "")
			return
		}
		if cur.Digest != digest {
			next.Revision++
		}
		next.Digest, next.Object, next.SealedTo, next.Node = digest, delivery.UserListObjectName(digest), delivery.SealingKeyID(key), in.BusNode
	}
	p.sayHeld(held)
	if next.Digest == digest {
		next.Users, next.LeftOut = users, leftOut
	}
	if next.Digest == "" {
		next.Users, next.LeftOut = 0, nil
	}
	if had && sameSealed(cur, next) {
		res.Sealed = sealedSays(cur, had, why)
		return
	}
	next.At = p.now()
	data, err := delivery.EncodeGrantsUserList(next)
	if err == nil {
		_, err = p.Store.Put(StateUserList, KeySealed, data)
	}
	if err != nil {
		res.Errors = append(res.Errors, fmt.Sprintf("its own %s %s cannot be written: %v", StateUserList, KeySealed, err))
		res.Sealed = sealedSays(cur, had, "")
		return
	}
	if next.Digest == digest && cur.Digest != digest {
		p.keepWrittenUsers(res, list, in.Hashes)
		p.keepSealedGrants(res, digest, list, composed)
		p.acceptedWritten(res, digest)
	}
	// The object the key named before is taken away once the key names the new one: the bucket keeps the list in force.
	if had && cur.Object != "" && cur.Object != next.Object {
		if err := p.Objects.DeleteObject(cur.Object); err != nil {
			res.Errors = append(res.Errors, "the sealed list before could not be taken away: "+err.Error())
		}
	}
	res.Sealed = sealedSays(next, true, why)
	p.say(res, EventUserList, map[string]any{"digest": next.Digest, "revision": next.Revision, "users": next.Users,
		"left_out": len(next.LeftOut), "follow": next.Follow, "sealed_to": next.Node})
}

// sayHeld raises the warning condition mesh-grants.user-list-held while the list in force is kept (why, which words the pass's
// `held: ...`), and clears it on the first pass that holds nothing back: the list advanced, or the reason went. The refusal
// condition's way (sayRefused): said once per reason, again when the reason changes, and tried again when a say failed.
func (p *Part) sayHeld(why string) {
	if p.Say == nil {
		return
	}
	p.holdMu.Lock()
	defer p.holdMu.Unlock()
	if p.heldKnown && why == p.heldSaid {
		return
	}
	c := asks.Condition{Key: HeldCondition, Subject: asks.Scope{Scope: "module", ID: "mesh-grants"}}
	if why == "" {
		c.State = asks.StateCleared
	} else {
		reason := strings.TrimPrefix(why, "held: ")
		c.Severity, c.State = asks.SeverityWarning, asks.StateRaised
		c.Summary, c.Headline, c.Needs = "the user list is held: "+reason, "The user list in force is held back", "a look at why"
		c.Explanation = asks.NeedsYou + "a look at why. The bus node keeps following the list written before, not the one composed now: " + reason
		c.Resolved = "a pass finds nothing to hold back and the list advances"
	}
	if p.Say(c) == nil {
		p.heldSaid, p.heldKnown = why, true
	}
}

// HeldCondition is the key of the warning raised while a list in force is held back.
const HeldCondition = "mesh-grants.user-list-held"

func sameSealed(a, b delivery.GrantsUserList) bool {
	// Its time is no change, and no user left out is the same written as [] or null: the key read back says [] for the
	// nil a pass composes, which read as a change wrote the key again at every pass, and each write moved the bus node's
	// report and woke the next pass (issue 1126: the shadow list's revision 99270 to 99357 in 90 s, 2026-10-28).
	a.At, b.At = b.At, a.At
	if len(a.LeftOut) == 0 {
		a.LeftOut = nil
	}
	if len(b.LeftOut) == 0 {
		b.LeftOut = nil
	}
	x, _ := json.Marshal(a)
	y, _ := json.Marshal(b)
	return string(x) == string(y)
}

// SealedState is what a pass says of the sealed list: the key as written, and why nothing was written when nothing was.
type SealedState struct {
	Written *delivery.GrantsUserList `json:"written,omitempty"`
	Why     string                   `json:"why,omitempty"`
}

func sealedSays(g delivery.GrantsUserList, had bool, why string) *SealedState {
	s := &SealedState{Why: why}
	if had {
		s.Written = &g
	}
	return s
}

func short(d string) string {
	d = strings.TrimPrefix(d, "sha256:")
	if len(d) > 12 {
		d = d[:12]
	}
	return d
}

// KeyWrittenUsers is the key of the state user-list naming the users of the list the key `sealed` names: what a list
// composed must keep.
const KeyWrittenUsers = "sealed-users"

// KeyWrittenCredentials is the key of the state user-list naming, per user of the list in force, which password its hash
// is of (credentialOf: adopted, or the vault's generation and fingerprint), never the hash: what tells a list that changes
// several loaded users' hashes at once (ADR 0561 §7).
const KeyWrittenCredentials = "sealed-credentials"

func (p *Part) keepWrittenUsers(res *Result, list []byte, hashes map[string]HeldHash) {
	users := listUsers(list)
	data, _ := json.Marshal(users)
	if _, err := p.Store.Put(StateUserList, KeyWrittenUsers, data); err != nil {
		res.Errors = append(res.Errors, fmt.Sprintf("its own %s %s cannot be written: %v", StateUserList, KeyWrittenUsers, err))
	}
	creds := map[string]string{}
	for _, u := range users {
		if h, ok := hashes[u]; ok {
			creds[u] = credentialOf(h)
		}
	}
	data, _ = json.Marshal(creds)
	if _, err := p.Store.Put(StateUserList, KeyWrittenCredentials, data); err != nil {
		res.Errors = append(res.Errors, fmt.Sprintf("its own %s %s cannot be written: %v", StateUserList, KeyWrittenCredentials, err))
	}
}

// changedHashes are the users of the list in force whose hash the list composed now would change with no rotation by the
// vault naming them (its announcement on the hash, or a node's login rotating in node-logins, ADR 0583 §2), sorted; none
// when the part kept no credentials of the list in force (a list written before).
func (p *Part) changedHashes(hashes map[string]HeldHash, rotating map[string]bool) ([]string, error) {
	raw, _, found, err := p.Store.Get(StateUserList, KeyWrittenCredentials)
	if err != nil || !found {
		return nil, err
	}
	var had map[string]string
	if err := json.Unmarshal(raw, &had); err != nil {
		return nil, err
	}
	var changed []string
	for user, was := range had {
		h, ok := hashes[user]
		if !ok || credentialOf(h) == was || h.Rotating != nil || rotating[user] {
			continue
		}
		changed = append(changed, user)
	}
	slices.Sort(changed)
	return changed, nil
}

var listUser = regexp.MustCompile(`\{\s*user:\s*"([^"]+)"`)

// listUsers names the users of a list as the composer writes it.
func listUsers(list []byte) []string {
	out := []string{}
	for _, m := range listUser.FindAllSubmatch(list, -1) {
		out = append(out, string(m[1]))
	}
	return out
}

// holdsBack says why a list composed now may not replace the one in force: a read failed this pass, a
// user of the list in force is left out for want of a hash, or the list would leave a seat the list in force holds with
// no holder while a placed module still claims it (lost, Holdings.LastHolders: the membership's guard, issue 1945; the
// loaded list not read holds it too, since that cannot be ruled out). The list in force is the one the part wrote, by the users
// it kept of it; where it kept none (a list written before this release), the users the bus loaded (bus, nil when
// they could not be read). Empty when it may.
func (p *Part) holdsBack(in Inputs, leftOut, dropped, bus, lost []string, digest string) string {
	p.hashHold = nil
	if f := in.ReadFailures(); len(f) > 0 {
		return "held: the list in force is kept while a read of this pass failed (" + strings.Join(f, "; ") + ")"
	}
	if bus == nil {
		return "held: the grants of the list in force cannot be read, so a loss of seats cannot be ruled out"
	}
	if len(lost) > 0 {
		return "held, " + ShadowDifference + "the last holder of " + strings.Join(lost, ", ")
	}
	raw, _, found, err := p.Store.Get(StateUserList, KeyWrittenUsers)
	if err != nil {
		return "held: the users of the list in force cannot be read: " + err.Error()
	}
	var had []string
	switch {
	case found:
		_ = json.Unmarshal(raw, &had)
	default:
		had = bus
	}
	var unhashed []string
	for _, u := range leftOut {
		if slices.Contains(had, u) {
			unhashed = append(unhashed, u)
		}
	}
	if len(unhashed) > 0 {
		return "held: the list in force is kept, since " + strings.Join(unhashed, ", ") + " would be left out for want of a hash in the vault"
	}
	// A refused principal the list in force carries and whose grants there the part did not keep: leaving it out would lock
	// it out of the bus (refused.go), so the list in force stands until its grants compose or are kept.
	var unkept []string
	for _, u := range dropped {
		if slices.Contains(had, u) {
			unkept = append(unkept, u)
		}
	}
	if len(unkept) > 0 {
		return "held: the list in force is kept, since " + strings.Join(unkept, ", ") + " would be left out: its grants are refused and the part kept none of the list in force"
	}
	// More than one loaded user's hash changing at once, with no rotation by the vault naming each (ADR 0561 §7): a new
	// writer of hashes must not lock several holders out in one list, as nine seats were cut on 2026-10-27 at 09:21.
	changed, err := p.changedHashes(in.Hashes, in.Rotating())
	if err != nil {
		return "held: the credentials of the list in force cannot be read: " + err.Error()
	}
	if len(changed) > 1 && !p.accepted(digest, changed) {
		p.hashHold = changed
		return "held: the list in force is kept, since the hashes of " + fmt.Sprint(len(changed)) + " loaded users would change at " +
			"once with no rotation by the vault naming them: " + strings.Join(changed, ", ")
	}
	return ""
}

// **A person accepts a held list's hash changes** (ADR 0561 §7, §9; tools-are-how-a-module-is-spoken-to): the hold of
// several loaded users' hashes changing at once is released only by grants_accept_hashes, naming exactly the users held,
// with why, bound to the held list's digest. The acceptance releases this guard alone, once: the other holds (a failed
// read, a user dropped for want of a hash, a lost right) stand whatever it says; and a list composed otherwise since is
// held again, for a new acceptance.

// KeyHashHold names the list held for its hash changes (its digest and the users), and KeyHashAccept a person's acceptance.
const (
	KeyHashHold   = "hash-hold"
	KeyHashAccept = "hash-accept"
)

// EventHashesAccepted is said when a list held for its hash changes is written on a person's acceptance: a hand act.
const EventHashesAccepted = "hashes-accepted"

// HashHold is the value of KeyHashHold, and HashAccept of KeyHashAccept.
type HashHold struct {
	Digest string    `json:"digest"`
	Users  []string  `json:"users"`
	At     time.Time `json:"at"`
}

type HashAccept struct {
	Digest string    `json:"digest"`
	Users  []string  `json:"users"`
	By     string    `json:"by"`
	Why    string    `json:"why"`
	At     time.Time `json:"at"`
}

// keepHashHold writes which list is held for its hash changes, when that is the hold.
func (p *Part) keepHashHold(res *Result, digest string) {
	if p.hashHold == nil {
		return
	}
	data, _ := json.Marshal(HashHold{Digest: digest, Users: p.hashHold, At: p.now()})
	if raw, _, found, err := p.Store.Get(StateUserList, KeyHashHold); err == nil && found {
		var was HashHold
		if json.Unmarshal(raw, &was) == nil && was.Digest == digest && slices.Equal(was.Users, p.hashHold) {
			return
		}
	}
	if _, err := p.Store.Put(StateUserList, KeyHashHold, data); err != nil {
		res.Errors = append(res.Errors, fmt.Sprintf("its own %s %s cannot be written: %v", StateUserList, KeyHashHold, err))
	}
}

// accepted says a person accepted exactly these users' hash changes of the list of this digest.
func (p *Part) accepted(digest string, users []string) bool {
	raw, _, found, err := p.Store.Get(StateUserList, KeyHashAccept)
	if err != nil || !found {
		return false
	}
	var a HashAccept
	return json.Unmarshal(raw, &a) == nil && a.Digest == digest && slices.Equal(a.Users, users)
}

// acceptedWritten says, once, that the list a person accepted is written, and forgets the acceptance and the hold.
func (p *Part) acceptedWritten(res *Result, digest string) {
	raw, _, found, err := p.Store.Get(StateUserList, KeyHashAccept)
	if err != nil || !found {
		return
	}
	var a HashAccept
	if json.Unmarshal(raw, &a) != nil || a.Digest != digest {
		return
	}
	p.say(res, EventHashesAccepted, map[string]any{"digest": digest, "users": a.Users, "by": a.By, "why": a.Why})
	for _, k := range []string{KeyHashAccept, KeyHashHold} {
		if err := p.Store.Delete(StateUserList, k); err != nil {
			res.Errors = append(res.Errors, fmt.Sprintf("its own %s %s cannot be taken away: %v", StateUserList, k, err))
		}
	}
}

// AcceptHashes is the tool accept-hashes: a person accepts the hash changes of the list held for them, naming exactly its
// users, with why. Refused when no list is held for its hashes, or for another set of users. Bound to the held list's
// digest: a list composed otherwise since is held again.
func (p *Part) AcceptHashes(caller string, users []string, why string) (any, error) {
	if strings.TrimSpace(why) == "" {
		return nil, errors.New("accept-hashes says why (`why`)")
	}
	raw, _, found, err := p.Store.Get(StateUserList, KeyHashHold)
	if err != nil {
		return nil, fmt.Errorf("the held list cannot be read: %w", err)
	}
	var h HashHold
	if !found || json.Unmarshal(raw, &h) != nil || h.Digest == "" {
		return nil, errors.New("no list is held for its users' hashes changing: there is nothing to accept")
	}
	named := slices.Sorted(slices.Values(users))
	if !slices.Equal(named, h.Users) {
		return nil, fmt.Errorf("the list held (%s) changes the hashes of %s: an acceptance names exactly those, and %s is not that",
			short(h.Digest), strings.Join(h.Users, ", "), strings.Join(named, ", "))
	}
	data, _ := json.Marshal(HashAccept{Digest: h.Digest, Users: h.Users, By: someoneOr(caller), Why: strings.TrimSpace(why), At: p.now()})
	rev, err := p.Store.Put(StateUserList, KeyHashAccept, data)
	if err != nil {
		return nil, fmt.Errorf("the acceptance could not be written: %w", err)
	}
	return map[string]any{"accepted": rev, "digest": h.Digest, "users": h.Users, "says": "the part's process writes the held " +
		"list at its next pass, once, unless another hold stands or the list composed then is another; it says hashes-accepted"}, nil
}

func someoneOr(caller string) string {
	if caller == "" {
		return "a caller the runtime did not prove"
	}
	return caller
}