package grants

import (
	"fmt"
	"slices"
	"sort"
	"strings"

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

// **One refused principal never freezes the list** (issue 774, sweep 2026-10-30; met twice that day: the engine's acts,
// then mesh-host_health). The composer refuses a principal's grants when they would make it a second writer of a state
// (buscompose.CheckWriters): that refusal used to end the whole composition, so the list in force stood for every principal
// while each change since piled up, and the next list that composed moved 52 users at once. Now each principal is composed
// on its own: one refused keeps the grants it holds in the list in force (the part's own record of that list, sealed
// grants), the rest of the list is composed and written as ever, and the refusal is raised as the warning
// mesh-grants.principal-refused, naming each principal and why, until it composes again. A refused principal the list in
// force does not carry stays out of the list: it never had those grants, and is refused them now.

// RefusedCondition is the key of the warning raised while a principal's grants are refused.
const RefusedCondition = "mesh-grants.principal-refused"

// ComposeEach is the shadow list composed principal by principal: every user whose grants compose, and each refused one
// by user with why. err is only for principals that cannot be derived at all (two users of one name). Pure.
func ComposeEach(r buscompose.Records) ([]User, map[string]string, error) {
	principals, err := buscompose.Users(r)
	if err != nil {
		return nil, nil, err
	}
	out := make([]User, 0, len(principals))
	refused := map[string]string{}
	for _, p := range principals {
		perms, err := buscompose.PermissionsFor(p)
		if err != nil {
			refused[p.Username()] = err.Error()
			continue
		}
		out = append(out, User{User: p.Username(), Publish: set(perms.Publish), Subscribe: set(perms.Subscribe),
			AllowResponses: perms.AllowResponses, PublishDeny: set(perms.PublishDeny)})
	}
	sort.Slice(out, func(i, j int) bool { return out[i].User < out[j].User })
	return out, refused, nil
}

// keptOf is, for each refused user, its grants in the list in force as the part sealed them; the users it holds none of
// (not in the list in force, or that list's grants not kept) are the second answer, sorted.
func (p *Part) keptOf(refused map[string]string) (map[string]User, []string) {
	if len(refused) == 0 {
		return nil, nil
	}
	var inForce map[string]User
	if g, _, had := p.Sealed(); had && g.Digest != "" && p.Store != nil {
		inForce, _ = p.sealedGrantsOf(g.Digest)
	}
	kept := map[string]User{}
	var none []string
	for _, user := range sortedKeys(refused) {
		if u, ok := inForce[user]; ok {
			kept[user] = u
			continue
		}
		none = append(none, user)
	}
	return kept, none
}

// withKept is users with each kept user in its place, sorted.
func withKept(users []User, kept map[string]User) []User {
	out := slices.Clone(users)
	for _, u := range kept {
		out = append(out, u)
	}
	sort.Slice(out, func(i, j int) bool { return out[i].User < out[j].User })
	return out
}

// keptEntry is a user of the accounts block from grants kept rather than composed, in ComposeAccounts' own lines
// (buscompose.AccountsEntry), so the bus reads it as it read the list in force.
func keptEntry(u User, hash string) string {
	return buscompose.AccountsEntry(u.User, hash, buscompose.Permissions{Publish: u.Publish, PublishDeny: u.PublishDeny,
		Subscribe: u.Subscribe, AllowResponses: u.AllowResponses})
}

// withEntries puts entries at the end of the accounts block's users, before it closes.
func withEntries(list string, entries []string) (string, error) {
	if len(entries) == 0 {
		return list, nil
	}
	start := strings.Index(list, "    users = [\n")
	if start < 0 {
		return "", fmt.Errorf("the composed list holds no users block to keep a refused user's grants in")
	}
	end := strings.Index(list[start:], "\n    ]\n")
	if end < 0 {
		return "", fmt.Errorf("the composed list's users block does not close")
	}
	at := start + end + 1
	return list[:at] + strings.Join(entries, "") + list[at:], nil
}

// sayPrincipalsRefused raises RefusedCondition while a principal's grants are refused, naming each with why and what
// became of it, and clears it once none is; said once per set, again when it changes, and at the first pass after a start.
func (p *Part) sayPrincipalsRefused(refused map[string]string, kept map[string]User) {
	if p.Say == nil {
		return
	}
	var lines []string
	for _, user := range sortedKeys(refused) {
		became := "left out of the list: the list in force does not carry it"
		if _, ok := kept[user]; ok {
			became = "keeps its grants of the list in force"
		}
		lines = append(lines, user+" ("+became+"): "+refused[user])
	}
	why := strings.Join(lines, "; ")
	p.holdMu.Lock()
	defer p.holdMu.Unlock()
	if p.refusedKnown && why == p.refusedSaid {
		return
	}
	c := asks.Condition{Key: RefusedCondition, Subject: asks.Scope{Scope: "module", ID: "mesh-grants"}}
	if why == "" {
		c.State = asks.StateCleared
	} else {
		c.Severity, c.State = asks.SeverityWarning, asks.StateRaised
		c.Summary = fmt.Sprintf("%d principal(s) refused their composed grants: %s", len(refused), why)
		c.Headline, c.Needs = "A principal's bus grants are refused", "a fix of the manifest or the writers table"
		c.Explanation = asks.NeedsYou + "a fix of what makes it a second writer. The rest of the user list is written as ever; " +
			"each refused principal keeps the grants the list in force gives it, or stays out where it holds none: " + why
		c.Resolved = "every principal's grants compose again"
	}
	if p.Say(c) == nil {
		p.refusedSaid, p.refusedKnown = why, true
	}
}