package inventory

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

	"github.com/jackc/pgx/v5"

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

// The reads of what a composition would make or hold, in one place and writing nothing (design 47 R4b, issue 1383): the
// controller's adapter from its stores to mesh-sdk's composition input asks them once for the whole mesh, where the
// composition's own reads (SecretFor, SharedSecretFor, ModuleSecretIfIssued, GivenOwnSecret) ask for one pair or one
// secret and make what is not held.

// OwnSecretRow is one own secret held on a machine (a module_secret row): who made it (`made`, or `accepted` for a
// value a person gave), the sealing key it is sealed to, and the value sealed to that key.
type OwnSecretRow struct {
	Node, Module, Name, Origin, SealedTo, Sealed string
}

// OwnSecretRows is every own secret held on every machine, by machine, module and name. It writes nothing.
func (i *Inventory) OwnSecretRows(ctx context.Context) ([]OwnSecretRow, error) {
	rows, err := i.store.Pool().Query(ctx,
		`select n.name, m.module, m.name, m.origin, m.node_key, m.sealed
		   from module_secret m join node n on n.id = m.node
		  order by n.name, m.module, m.name`)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var out []OwnSecretRow
	for rows.Next() {
		var r OwnSecretRow
		if err := rows.Scan(&r.Node, &r.Module, &r.Name, &r.Origin, &r.SealedTo, &r.Sealed); err != nil {
			return nil, err
		}
		out = append(out, r)
	}
	return out, rows.Err()
}

// PairState is how one pair credential stands, as the composition's reads of it would find it (what SecretFor,
// SharedSecretFor and GivenPairSecret answer), without making anything.
type PairState struct {
	// State is one of the Pair constants.
	State string
	// Sealed is the consumer's copy as it is sealed to the consumer's key, for a held credential.
	Sealed string
	// Why is the controller's words for a credential not given or refused.
	Why string
}

// The states of a pair credential.
const (
	// PairHeld is a credential held, sealed to the keys both ends have now.
	PairHeld = "held"
	// PairWouldMake is a credential the next send makes.
	PairWouldMake = "would-make"
	// PairNotGiven is a credential only a person gives (novox/hq ADR 0337), which nobody gave under the keys the ends have now.
	PairNotGiven = "not-given"
	// PairRefused is a credential the next send would be refused when it made it, for the reason Why gives.
	PairRefused = "refused"
)

// PairCredentialKind says which of the controller's reads a pair is answered by.
type PairCredentialKind int

const (
	// PairPlain is a credential made for the pair (SecretFor).
	PairPlain PairCredentialKind = iota
	// PairShared is the provider's one credential sealed to the consumer too (SharedSecretFor; Own names the provider's own secret).
	PairShared
	// PairOutside is a credential only a person gives (GivenPairSecret).
	PairOutside
)

// PairCredential is one pair credential, by the ends it joins.
type PairCredential struct {
	Kind                                                            PairCredentialKind
	Name, Consumer, ConsumerModule, Provider, ProviderModule, Local string
	// Own is, for a shared credential, the provider's own secret it is.
	Own string
}

// PairCredentialState says how a pair credential stands now, by the rules the next send applies and without applying
// them: nothing is inserted, remade or sealed. A credential the send would make is PairWouldMake, unless the send would be
// refused (a machine with no sealing key, a value given and sealed to a key one end no longer has), which is PairRefused
// in the send's own words.
func (i *Inventory) PairCredentialState(ctx context.Context, p PairCredential) (PairState, error) {
	switch p.Kind {
	case PairOutside:
		return i.outsideState(ctx, p)
	case PairShared:
		return i.sharedState(ctx, p)
	}
	return i.plainState(ctx, p)
}

func (i *Inventory) outsideState(ctx context.Context, p PairCredential) (PairState, error) {
	got, err := i.GivenPairSecret(ctx, p.Name, p.Consumer, p.ConsumerModule, p.Provider, p.ProviderModule, p.Local)
	var notGiven *NotGivenError
	switch {
	case errors.As(err, &notGiven):
		return PairState{State: PairNotGiven, Why: notGiven.Why}, nil
	case err != nil:
		return PairState{}, err
	}
	return PairState{State: PairHeld, Sealed: got.ForConsumer}, nil
}

func (i *Inventory) plainState(ctx context.Context, p PairCredential) (PairState, error) {
	consumerKey, err := i.SealingKeyOf(ctx, p.Consumer)
	if err != nil {
		return PairState{}, err
	}
	providerKey, err := i.SealingKeyOf(ctx, p.Provider)
	if err != nil {
		return PairState{}, err
	}
	consumerNode, err := i.NodeByName(ctx, p.Consumer)
	if err != nil {
		return PairState{}, err
	}
	providerNode, err := i.NodeByName(ctx, p.Provider)
	if err != nil {
		return PairState{}, err
	}
	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`,
		p.Name, consumerNode.ID, p.ConsumerModule, providerNode.ID, p.Local).
		Scan(&held.ForConsumer, &held.ForProvider, &held.ConsumerKey, &held.ProviderKey, &held.Origin)
	if err != nil && !errors.Is(err, pgx.ErrNoRows) {
		return PairState{}, err
	}
	if err == nil && held.ConsumerKey == consumerKey && held.ProviderKey == providerKey {
		return PairState{State: PairHeld, Sealed: held.ForConsumer}, nil
	}
	if err == nil && held.Origin == OriginAccepted {
		return PairState{State: PairRefused, Why: fmt.Sprintf(
			"%s's %q credential from %s was accepted from a person, and a sealing key at one end "+
				"has changed since. The mesh cannot re-seal a value it does not hold: accept it "+
				"again with `secret accept %s %s %s --provider %s%s`",
			p.ConsumerModule, p.Name, p.Provider, p.Consumer, p.ConsumerModule, p.Name, p.Provider, localFlag(p.Local))}, nil
	}
	// What making one would meet: the operator's key and the two sealing keys, by the same call that seals them.
	operator, err := i.OperatorKey(ctx)
	if err != nil {
		return PairState{}, err
	}
	if _, _, merr := secrets.MakeWithOperator(consumerKey, providerKey, operator); merr != nil {
		return PairState{State: PairRefused, Why: merr.Error()}, nil
	}
	return PairState{State: PairWouldMake}, nil
}

func (i *Inventory) sharedState(ctx context.Context, p PairCredential) (PairState, error) {
	consumerKey, err := i.SealingKeyOf(ctx, p.Consumer)
	if err != nil {
		return PairState{}, err
	}
	consumerNode, err := i.NodeByName(ctx, p.Consumer)
	if err != nil {
		return PairState{}, err
	}
	providerNode, err := i.NodeByName(ctx, p.Provider)
	if err != nil {
		return PairState{}, err
	}
	providerKey, err := i.SealingKeyOf(ctx, p.Provider)
	if err != nil {
		return PairState{}, err
	}
	if consumerKey == "" || providerKey == "" {
		return PairState{State: PairRefused, Why: fmt.Sprintf("%s and %s both need a sealing key before %s can be shared",
			p.Consumer, p.Provider, p.Name)}, nil
	}
	var ownGeneration, ownOrigin, ownKey *string
	err = i.store.Pool().QueryRow(ctx,
		`select generation, origin, node_key from module_secret where node = $1 and module = $2 and name = $3`,
		providerNode.ID, p.ProviderModule, p.Own).Scan(&ownGeneration, &ownOrigin, &ownKey)
	if err != nil && !errors.Is(err, pgx.ErrNoRows) {
		return PairState{}, err
	}
	var held Secret
	var pairGeneration *string
	err = i.store.Pool().QueryRow(ctx,
		`select for_consumer, for_provider, consumer_key, provider_key, origin, generation from secret
		 where name = $1 and consumer = $2 and consumer_module = $3 and provider = $4 and local = $5`,
		p.Name, consumerNode.ID, p.ConsumerModule, providerNode.ID, p.Local).
		Scan(&held.ForConsumer, &held.ForProvider, &held.ConsumerKey, &held.ProviderKey, &held.Origin, &pairGeneration)
	if err != nil && !errors.Is(err, pgx.ErrNoRows) {
		return PairState{}, err
	}
	current := ownGeneration != nil && pairGeneration != nil && *ownGeneration == *pairGeneration &&
		held.ConsumerKey == consumerKey && held.ProviderKey == providerKey && ownKey != nil && *ownKey == providerKey
	if current {
		return PairState{State: PairHeld, Sealed: held.ForConsumer}, nil
	}
	if _, outside, err := i.ownIssuedOutside(ctx, p.ProviderModule, p.Own); err != nil {
		return PairState{}, err
	} else if outside && (ownOrigin == nil || *ownOrigin != OriginAccepted) {
		return PairState{State: PairNotGiven,
			Why: "nobody gave " + p.ProviderModule + "'s own secret " + p.Own + ", which is issued outside the mesh"}, nil
	}
	if ownOrigin != nil && *ownOrigin == OriginAccepted {
		return PairState{State: PairRefused, Why: fmt.Sprintf(
			"%s on %s needs %s from %s, whose credential is %s's own secret %q — a value given to the "+
				"mesh, which cannot seal it to a consumer that binds later (ADR 0158): `secret accept %s %s %s` "+
				"again, which seals it to every current consumer",
			p.ConsumerModule, p.Consumer, p.Name, p.Provider, p.ProviderModule, p.Own, p.Provider, p.ProviderModule, p.Own)}, nil
	}
	return PairState{State: PairWouldMake}, nil
}

// BusMinted is the name of every bus user the mesh has minted a password hash for: `<node>.<module>` for a module and
// `provisioner.<node>` for a machine's provisioner client.
func (i *Inventory) BusMinted(ctx context.Context) ([]string, error) {
	kept, err := i.BusUsers(ctx)
	if err != nil {
		return nil, err
	}
	out := make([]string, 0, len(kept))
	for name := range kept {
		out = append(out, name)
	}
	sort.Strings(out)
	return out, nil
}