package main

// What the `oidc-client` provision means in Keycloak: one confidential OpenID Connect client per
// consumer, in the realm this module serves, under the name and secret the mesh gave both ends.
// Ported from oidc.ts, behaviour for behaviour.
//
// **The client id and the secret are the mesh's, not Keycloak's (novox/hq ADR 0048).** The mesh
// derives the consumer's identity (`as`) and hands it to both ends, and mints the secret, which this
// sets as the client's secret. Keycloak generates neither.
//
// **Where the consumer's browser comes back to is the consumer's to say.** Its contribution carries
// `callback` (a path) and the mesh composes its endpoint's names into `name` (public) and
// `internal-name` (private network) exactly as it does for a route (novox/hq ADR 0056, 0138).
//
// **Only what the mesh made is touched.** A client this module creates carries the attribute
// `mesh.provisioned=true`. A client with the same id that lacks the mark is somebody else's: it is
// refused, never adopted, never updated, never deleted.
//
// **Retired is the client disabled and marked** (novox/hq ADR 0230). `enabled: false` — Keycloak then
// refuses the client's authorization and token requests, so nobody signs in through it — and the
// attributes `mesh.retired` (when) and `mesh.retired-why` (why). Its secret, redirects, mappers and
// every other setting are kept, so asked for again it is enabled as it was: Ensure sets `enabled` and
// removes the two attributes. Deleted — only through `cleanup delete` — the client is removed.

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"net/url"
	"regexp"
	"sort"
	"strings"
	"time"
)

// Mark is the attribute marking a client as the mesh's own work.
const Mark = "mesh.provisioned"

// MarkRetired and MarkRetiredWhy mark a retired client: when and why (novox/hq ADR 0230).
const (
	MarkRetired    = "mesh.retired"
	MarkRetiredWhy = "mesh.retired-why"
)

// RolesMapper is the mapper every mesh client carries: realm roles as a flat `roles` claim in the id
// token, the access token and userinfo — what a consumer maps its own roles from.
func RolesMapper() Rep {
	return Rep{
		"name":           "realm roles",
		"protocol":       "openid-connect",
		"protocolMapper": "oidc-usermodel-realm-role-mapper",
		"config": map[string]any{
			"claim.name":           "roles",
			"jsonType.label":       "String",
			"multivalued":          "true",
			"id.token.claim":       "true",
			"access.token.claim":   "true",
			"userinfo.token.claim": "true",
		},
	}
}

var realmPath = regexp.MustCompile(`/realms/([^/]+)/?$`)

// RealmOf is the realm named by an issuer URL — `https://id.example/realms/Novox` is realm `Novox`.
// The issuer is the one value an assignment sets, so the realm is read out of it rather than set a
// second time where the two could disagree.
func RealmOf(issuer string) (string, error) {
	u, err := url.Parse(issuer)
	if err != nil || u.Scheme == "" || u.Host == "" {
		return "", fmt.Errorf("the issuer %q is not a URL", issuer)
	}
	m := realmPath.FindStringSubmatch(u.EscapedPath())
	if m == nil {
		return "", fmt.Errorf("the issuer %q does not end in /realms/<realm>", issuer)
	}
	realm, err := url.PathUnescape(m[1])
	if err != nil {
		return "", err
	}
	return realm, nil
}

// RedirectsOf is the redirect URIs a consumer's contribution asks for: its callback under each name
// the mesh composed for its endpoint. Refused when there is nothing to register.
func RedirectsOf(values map[string]any) (root string, redirects []string, err error) {
	callback, _ := values["callback"].(string)
	if !strings.HasPrefix(callback, "/") {
		raw, _ := json.Marshal(values["callback"])
		return "", nil, fmt.Errorf("contributes no callback path (`callback`, starting with \"/\"): %s", raw)
	}
	var names []string
	for _, key := range []string{"name", "internal-name"} {
		n, _ := values[key].(string)
		n = strings.TrimSpace(n)
		if n != "" && !contains(names, n) {
			names = append(names, n)
		}
	}
	if len(names) == 0 {
		return "", nil, errors.New("has no name the mesh composed (`name` / `internal-name`) — contribute a `label` and the `endpoint` it is reached on")
	}
	for _, n := range names {
		redirects = append(redirects, "https://"+n+callback)
	}
	return "https://" + names[0], redirects, nil
}

func contains(list []string, s string) bool {
	for _, x := range list {
		if x == s {
			return true
		}
	}
	return false
}

// wanted is the fields the mesh owns on a client it made. Everything else is left as found.
func wanted(p Provision) (Rep, []string, error) {
	root, redirects, err := RedirectsOf(p.Values)
	if err != nil {
		return nil, nil, err
	}
	whose := "a consumer"
	if p.Consumer != "" {
		whose = "a module on " + p.Consumer
	}
	uris := make([]any, len(redirects))
	for i, r := range redirects {
		uris[i] = r
	}
	return Rep{
		"clientId":                  p.As,
		"name":                      p.As,
		"description":               "made by the mesh for " + whose + " — do not edit; it is reset",
		"enabled":                   true,
		"protocol":                  "openid-connect",
		"publicClient":              false,
		"clientAuthenticatorType":   "client-secret",
		"secret":                    p.Password,
		"rootUrl":                   root,
		"baseUrl":                   root,
		"redirectUris":              uris,
		"standardFlowEnabled":       true,
		"implicitFlowEnabled":       false,
		"directAccessGrantsEnabled": false,
		"serviceAccountsEnabled":    false,
	}, redirects, nil
}

func stringList(v any) []string {
	list, _ := v.([]any)
	out := make([]string, 0, len(list))
	for _, x := range list {
		if s, ok := x.(string); ok {
			out = append(out, s)
		}
	}
	return out
}

func sameSet(a, b []string) bool {
	x, y := append([]string(nil), a...), append([]string(nil), b...)
	sort.Strings(x)
	sort.Strings(y)
	if len(x) != len(y) {
		return false
	}
	for i := range x {
		if x[i] != y[i] {
			return false
		}
	}
	return true
}

func attributes(c Rep) map[string]any {
	if a, ok := c["attributes"].(map[string]any); ok {
		return a
	}
	return map[string]any{}
}

func marked(c Rep) bool { return attributes(c)[Mark] == "true" }

// OidcClients is the provision's meaning in one realm.
type OidcClients struct {
	KC    *Client
	Realm string
}

// Ensure creates the consumer's client, or brings the mesh's existing one back to what the grant
// says. Answers "created" or "updated". Idempotent.
func (o OidcClients) Ensure(ctx context.Context, p Provision) (string, error) {
	want, _, err := wanted(p)
	if err != nil {
		return "", err
	}
	found, err := o.KC.FindClient(ctx, o.Realm, p.As)
	if err != nil {
		return "", err
	}
	if found != nil && !marked(found) {
		return "", fmt.Errorf("realm %s already has a client %s the mesh did not make — left alone; "+
			"delete or rename it if the mesh should own that id", o.Realm, p.As)
	}
	if found == nil {
		want["attributes"] = map[string]any{Mark: "true"}
		want["protocolMappers"] = []any{RolesMapper()}
		if err := o.KC.CreateClient(ctx, o.Realm, want); err != nil {
			return "", err
		}
		return "created", nil
	}
	// Overlay what the mesh owns on what is there, so a field Keycloak added or an operator set on a
	// field the mesh does not own survives the update.
	merged := Rep{}
	for k, v := range found {
		merged[k] = v
	}
	for k, v := range want {
		merged[k] = v
	}
	attrs := map[string]any{}
	for k, v := range attributes(found) {
		attrs[k] = v
	}
	attrs[Mark] = "true"
	// Asked for again: no longer marked to delete (novox/hq ADR 0230).
	delete(attrs, MarkRetired)
	delete(attrs, MarkRetiredWhy)
	merged["attributes"] = attrs
	id, _ := found["id"].(string)
	if err := o.KC.UpdateClient(ctx, o.Realm, id, merged); err != nil {
		return "", err
	}
	return "updated", o.ensureMapper(ctx, id)
}

func (o OidcClients) ensureMapper(ctx context.Context, id string) error {
	want := RolesMapper()
	mappers, err := o.KC.ListClientMappers(ctx, o.Realm, id)
	if err != nil {
		return err
	}
	var have Rep
	for _, m := range mappers {
		if m["name"] == want["name"] {
			have = m
			break
		}
	}
	if have == nil {
		return o.KC.AddClientMapper(ctx, o.Realm, id, want)
	}
	drifted := have["protocolMapper"] != want["protocolMapper"]
	hc, _ := have["config"].(map[string]any)
	for k, v := range want["config"].(map[string]any) {
		if hc[k] != v {
			drifted = true
		}
	}
	if drifted {
		want["id"] = have["id"]
		return o.KC.UpdateClientMapper(ctx, o.Realm, id, want)
	}
	return nil
}

// Holds says whether Keycloak still holds this consumer's client exactly as the grant says: present,
// the mesh's, enabled, confidential, with the mesh's secret and the redirects asked for. Reads only.
func (o OidcClients) Holds(ctx context.Context, p Provision) (bool, error) {
	_, redirects, err := wanted(p)
	if err != nil {
		return false, err
	}
	found, err := o.KC.FindClient(ctx, o.Realm, p.As)
	if err != nil {
		return false, err
	}
	if found == nil || !marked(found) || found["enabled"] == false || found["publicClient"] == true {
		return false, nil
	}
	if !sameSet(stringList(found["redirectUris"]), redirects) {
		return false, nil
	}
	id, _ := found["id"].(string)
	mappers, err := o.KC.ListClientMappers(ctx, o.Realm, id)
	if err != nil {
		return false, err
	}
	hasMapper := false
	for _, m := range mappers {
		if m["name"] == RolesMapper()["name"] {
			hasMapper = true
		}
	}
	if !hasMapper {
		return false, nil
	}
	secret, err := o.KC.ClientSecretByID(ctx, o.Realm, id)
	if err != nil {
		return false, err
	}
	return secret == p.Password, nil
}

// Retire disables a consumer's client — only one the mesh made — and marks it with when and why.
// Answers what happened: "retired", "absent" or "not ours".
func (o OidcClients) Retire(ctx context.Context, as, why string, at time.Time) (string, error) {
	found, err := o.KC.FindClient(ctx, o.Realm, as)
	if err != nil {
		return "", err
	}
	if found == nil {
		return "absent", nil
	}
	if !marked(found) {
		return "not ours", nil
	}
	merged := Rep{}
	for k, v := range found {
		merged[k] = v
	}
	attrs := map[string]any{}
	for k, v := range attributes(found) {
		attrs[k] = v
	}
	attrs[MarkRetired] = at.UTC().Format(time.RFC3339)
	attrs[MarkRetiredWhy] = why
	merged["attributes"] = attrs
	merged["enabled"] = false
	id, _ := found["id"].(string)
	return "retired", o.KC.UpdateClient(ctx, o.Realm, id, merged)
}

// Inventory is every client in the realm the mesh made: enabled ones active, disabled ones retired —
// with when and why from the mark, or none for one disabled before the mark existed.
func (o OidcClients) Inventory(ctx context.Context) (Inventory, error) {
	inv := Inventory{Active: []string{}, Retired: []Retired{}}
	clients, err := o.KC.ListClients(ctx, o.Realm)
	if err != nil {
		return inv, err
	}
	for _, c := range clients {
		if !marked(c) {
			continue
		}
		id, _ := c["clientId"].(string)
		a := attributes(c)
		when, _ := a[MarkRetired].(string)
		if c["enabled"] != false && when == "" {
			inv.Active = append(inv.Active, id)
			continue
		}
		at, _ := time.Parse(time.RFC3339, when)
		why, _ := a[MarkRetiredWhy].(string)
		inv.Retired = append(inv.Retired, Retired{Consumer: id, RetiredAt: at, Why: why, SizeBytes: -1, Kind: KindConsumer})
	}
	return inv, nil
}

// Delete removes a retired client — only one the mesh made, and only while it is disabled.
func (o OidcClients) Delete(ctx context.Context, as string) error {
	found, err := o.KC.FindClient(ctx, o.Realm, as)
	if err != nil {
		return err
	}
	if found == nil {
		return nil
	}
	if !marked(found) {
		return fmt.Errorf("realm %s's client %s was not made by the mesh — left alone", o.Realm, as)
	}
	if found["enabled"] != false {
		return fmt.Errorf("client %s is enabled — it is active, not retired, and is not deleted", as)
	}
	id, _ := found["id"].(string)
	return o.KC.DeleteClientByID(ctx, o.Realm, id)
}