package inventory

import (
	"context"
	"errors"
	"fmt"
	"sort"

	"github.com/jackc/pgx/v5"

	"github.com/novox/mesh-controller/internal/catalogue"
	"github.com/novox/mesh-controller/internal/secrets"
)

// A provision whose credential only a person outside the mesh can give (novox/hq ADR 0337, issue 164): a Servarr
// app's API key, an indexer's key, a downloader's password. The provider's software holds the value; the mesh can
// neither make one that would work nor fetch it. So the mesh never makes one (§2), a person gives it once per
// provider and it is sealed to every consumer of that provider (§3), and until then a consumer holds no credential
// for it and is told so (§4), and the rest of it runs.

// NotGivenError is a pair credential only a person can give, which no person gave for this pair under the keys its
// two ends have now: the consumer receives no credential for it, and waits (ADR 0337 §4, §8). It is not a fault of
// the machine, so the plan does not refuse the machine for it.
type NotGivenError struct {
	Provision, Consumer, ConsumerModule, Provider, ProviderModule, Local string
	// Own is set when the credential is the provider's own secret issued outside (ADR 0158, ADR 0228), and names it.
	Own string
	// Why is why no value is held, in words that never carry one.
	Why string
}

func (e *NotGivenError) Error() string {
	if e.Own != "" {
		return fmt.Sprintf("%s on %s holds no %s from %s: %s; give it with `secret accept %s %s %s`",
			e.ConsumerModule, e.Consumer, e.Provision, e.Provider, e.Why, e.Provider, e.ProviderModule, e.Own)
	}
	return fmt.Sprintf("%s on %s holds no %s from %s: %s; it is issued outside the mesh and given with `%s`",
		e.ConsumerModule, e.Consumer, e.Provision, e.Provider, e.Why, acceptLine(e.Provider, e.ProviderModule, e.Provision))
}

// IsNotGiven is whether an error is a credential only a person gives, not given yet.
func IsNotGiven(err error) bool {
	var ng *NotGivenError
	return errors.As(err, &ng)
}

// acceptLine is the one line that gives a provision's credential issued outside, for every consumer of a provider.
func acceptLine(provider, providerModule, provision string) string {
	if providerModule == "" {
		providerModule = "<provider module>"
	}
	return fmt.Sprintf("secret accept %s %s %s", provider, providerModule, provision)
}

// AcceptLine is acceptLine, for the controller's words.
func AcceptLine(provider, providerModule, provision string) string {
	return acceptLine(provider, providerModule, provision)
}

// issuedOutside is whether a module in the catalogue offers the provision with a credential issued outside the
// mesh, and which.
func (i *Inventory) issuedOutside(ctx context.Context, provision string) (string, bool, error) {
	shelf, err := i.Catalogue(ctx)
	if err != nil {
		return "", false, err
	}
	module, outside := catalogue.OffersIssuedOutside(shelf, provision)
	return module, outside, nil
}

// ownIssuedOutside is whether a provider's own secret says only an outside party issues it (ADR 0228).
func (i *Inventory) ownIssuedOutside(ctx context.Context, providerModule, own string) (string, bool, error) {
	if providerModule == "" {
		return own, false, nil
	}
	m, err := i.declared(ctx, providerModule)
	if err != nil {
		return own, false, err
	}
	return own, m.OwnSecrets[own].IssuedBy == catalogue.IssuedOutside, nil
}

// GivenPairSecret is the credential of a pair whose provision is issued outside the mesh, as a person gave it, and
// never one the mesh makes (ADR 0337 §2, §4). It writes nothing. A value is answered only when a person gave it
// (`accepted`) and it is sealed to the keys both ends have now; otherwise a NotGivenError says why — never given, or
// given under a key one end no longer has (§8), or a value the mesh made before the rule, which is not given and
// never delivered again (§2).
func (i *Inventory) GivenPairSecret(ctx context.Context, name, consumer, consumerModule, provider, providerModule,
	local string) (Secret, error) {
	consumerKey, err := i.SealingKeyOf(ctx, consumer)
	if err != nil {
		return Secret{}, err
	}
	providerKey, err := i.SealingKeyOf(ctx, provider)
	if err != nil {
		return Secret{}, err
	}
	consumerNode, err := i.NodeByName(ctx, consumer)
	if err != nil {
		return Secret{}, err
	}
	providerNode, err := i.NodeByName(ctx, provider)
	if err != nil {
		return Secret{}, err
	}
	notGiven := func(why string) (Secret, error) {
		return Secret{}, &NotGivenError{Provision: name, Consumer: consumer, ConsumerModule: consumerModule,
			Provider: provider, ProviderModule: providerModule, Local: local, Why: why}
	}
	var held Secret
	err = i.store.Pool().QueryRow(ctx,
		`select for_consumer, for_provider, consumer_key, provider_key, origin from secret
		 where name = $1 and consumer = $2 and consumer_module = $3 and provider = $4 and local = $5`,
		name, consumerNode.ID, consumerModule, providerNode.ID, local).
		Scan(&held.ForConsumer, &held.ForProvider, &held.ConsumerKey, &held.ProviderKey, &held.Origin)
	switch {
	case errors.Is(err, pgx.ErrNoRows):
		return notGiven("nobody gave it")
	case err != nil:
		return Secret{}, err
	case held.Origin != OriginAccepted:
		return notGiven("the value held was made by the mesh, which " + providerModule + "'s software would refuse")
	case consumerKey == "" || providerKey == "" || held.ConsumerKey != consumerKey || held.ProviderKey != providerKey:
		return notGiven("it was given under a sealing key one end no longer has")
	}
	held.Name, held.Consumer, held.Provider = name, consumer, provider
	held.ConsumerModule, held.Local = consumerModule, local
	return held, nil
}

// PairEnd is one consumer of a provision from one provider: the machine, the module there and its local name.
type PairEnd struct {
	Consumer, ConsumerModule, Local string
}

// ProvisionAccepted is what one accept for a provider sealed (ADR 0337 §3): the consumers it reached, those it could
// not (no sealing key on their machine), and the machines to send.
type ProvisionAccepted struct {
	Sealed, Unsealable []PairEnd
	Machines           []string
}

// AcceptSecretForProvision seals one value a person gave for a provision issued outside the mesh to the provider's
// machine, to every consumer named, and to the operator, in one act under one generation, each row `accepted`
// (ADR 0337 §3, issue 165); the plaintext is not kept. The consumers are every one that binds the provision from
// this provider now, which the caller finds by resolving every machine. A consumer whose machine has no sealing key
// is not sealed to, and said.
func (i *Inventory) AcceptSecretForProvision(ctx context.Context, provision, provider, providerModule, value string,
	consumers []PairEnd) (ProvisionAccepted, error) {
	m, err := i.declared(ctx, providerModule)
	if err != nil {
		return ProvisionAccepted{}, err
	}
	if !m.IssuedOutsideOf(provision) {
		return ProvisionAccepted{}, fmt.Errorf("%s does not offer %q with a credential issued outside the mesh "+
			"(\"credential\": {\"issued-by\": \"outside\"}, ADR 0337), so its consumers' credentials are not given "+
			"once for the provider", providerModule, provision)
	}
	if value == "" {
		return ProvisionAccepted{}, errors.New("there is nothing to seal")
	}
	providerNode, err := i.NodeByName(ctx, provider)
	if err != nil {
		return ProvisionAccepted{}, err
	}
	providerKey, err := i.SealingKeyOf(ctx, provider)
	if err != nil {
		return ProvisionAccepted{}, err
	}
	if providerKey == "" {
		return ProvisionAccepted{}, fmt.Errorf("%s has no sealing key, so nothing can be sealed to it; a node joins to get one", provider)
	}
	forOperator, operatorKey, err := i.operatorSeal(ctx, value)
	if err != nil {
		return ProvisionAccepted{}, err
	}
	generation := secrets.Stamp()
	var out ProvisionAccepted
	machines := map[string]bool{provider: true}
	tx, err := i.store.Pool().Begin(ctx)
	if err != nil {
		return ProvisionAccepted{}, err
	}
	defer func() { _ = tx.Rollback(ctx) }()
	for _, c := range consumers {
		consumerNode, err := i.NodeByName(ctx, c.Consumer)
		if err != nil {
			return ProvisionAccepted{}, err
		}
		consumerKey, err := i.SealingKeyOf(ctx, c.Consumer)
		if err != nil {
			return ProvisionAccepted{}, err
		}
		if consumerKey == "" {
			out.Unsealable = append(out.Unsealable, c)
			continue
		}
		sealed, err := secrets.Accept(value, consumerKey, providerKey)
		if err != nil {
			return ProvisionAccepted{}, err
		}
		if _, err := tx.Exec(ctx,
			`insert into secret (name, consumer, consumer_module, provider, for_consumer, for_provider,
			                     consumer_key, provider_key, operator_sealed, operator_key, origin, local, generation)
			 values ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13)
			 on conflict (name, local, consumer, consumer_module, provider) do update set
			   for_consumer = excluded.for_consumer, for_provider = excluded.for_provider,
			   consumer_key = excluded.consumer_key, provider_key = excluded.provider_key,
			   created_at = now(), origin = excluded.origin, generation = excluded.generation,
			   operator_sealed = excluded.operator_sealed, operator_key = excluded.operator_key`,
			provision, consumerNode.ID, c.ConsumerModule, providerNode.ID,
			sealed.ForConsumer, sealed.ForProvider, sealed.ConsumerKey, sealed.ProviderKey,
			forOperator, operatorKey, OriginAccepted, c.Local, generation); err != nil {
			return ProvisionAccepted{}, err
		}
		out.Sealed = append(out.Sealed, c)
		machines[c.Consumer] = true
	}
	if err := tx.Commit(ctx); err != nil {
		return ProvisionAccepted{}, err
	}
	for n := range machines {
		out.Machines = append(out.Machines, n)
	}
	sort.Strings(out.Machines)
	return out, nil
}

// GivenPairsOf is every provision a module on a machine holds a value a person gave for, sealed to the keys both
// ends have now: what a wait for a provision's credential is checked against (ADR 0337 §6).
func (i *Inventory) GivenPairsOf(ctx context.Context, machine, module string) (map[string]bool, error) {
	rows, err := i.store.Pool().Query(ctx,
		`select s.name
		   from secret s
		   join node c on c.id = s.consumer
		   join node p on p.id = s.provider
		  where c.name = $1 and s.consumer_module = $2 and s.origin = 'accepted'
		    and s.consumer_key = c.sealing_key and s.provider_key = p.sealing_key`, machine, module)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	out := map[string]bool{}
	for rows.Next() {
		var name string
		if err := rows.Scan(&name); err != nil {
			return nil, err
		}
		out[name] = true
	}
	return out, rows.Err()
}