package signedjobs

import (
	"context"
	"encoding/json"
	"fmt"
	"log/slog"
)

// opDecommission is the op class this executor serves (mirrors reconcile.ClassDecommission; the
// literal avoids importing reconcile here just for the string).
const opDecommission = "decommission"

// IntentDecommissioner records a PERMANENT drive decommission keyed by the drive's storage
// durable-id. Satisfied by *storage.IntentStore (SetDecommissioned). Decommission is the operator's
// "permanent removal" intent: once recorded, the self-heal watchdog never auto-mounts the drive
// again (it SURVIVES absent/present), cleared only by an explicit re-commission.
type IntentDecommissioner interface {
	SetDecommissioned(durableID string) error
}

// decommissionParams is the verified params of a decommission op. The drive is named by its STORAGE
// durable-id — the SAME key the storage observer / watchdog use (e.g. "uuid:<fs-uuid>"), NOT the
// device-level byid:/byuuid: scheme the storage_wipe op uses. That is deliberate: decommission
// manipulates the intent MAP the watchdog reads, so the signed id must be the watchdog's key or the
// recorded intent would never gate a remount.
type decommissionParams struct {
	DurableID string `json:"durable_id"`
}

// DecommissionExecutor is the operator "permanent removal" consumer (slice 10 P3 completion). It
// makes the previously-unreachable IntentDecommissioned state reachable — but ONLY via a gate-
// VERIFIED operator signature (decommission is classified destructive in reconcile.Classify, so the
// signed-jobs gate refuses it pending_signature without a valid operator signature). It is distinct
// from a customer-confirmable safe eject: permanent removal is never customer-authorizable.
//
// The binding IS the durable-id: the signed op authorizes decommissioning exactly that drive on
// exactly the signed host (host_scope is checked by the gate). No /dev resolution is needed — and
// none is wanted, because a drive can legitimately be decommissioned while physically ABSENT.
type DecommissionExecutor struct {
	intent IntentDecommissioner
	logger *slog.Logger
}

// NewDecommissionExecutor wires the executor to the agent's intent store.
func NewDecommissionExecutor(intent IntentDecommissioner, logger *slog.Logger) *DecommissionExecutor {
	if logger == nil {
		logger = slog.Default()
	}
	return &DecommissionExecutor{intent: intent, logger: logger}
}

// Execute implements signedjobs.Executor for the decommission op class.
func (d *DecommissionExecutor) Execute(_ context.Context, op string, params json.RawMessage) error {
	if op != opDecommission {
		return ErrNoExecutor // not ours — the runner leaves it queued for the owning executor
	}
	if d.intent == nil {
		// No intent store on this host (open failure) → the op can't be honored. Don't clear it as
		// "done"; surface a hard error so the runner logs it and the operator can retry once fixed.
		return fmt.Errorf("decommission: no intent store wired on this host — cannot record decommission")
	}
	var p decommissionParams
	if err := json.Unmarshal(params, &p); err != nil {
		return fmt.Errorf("decommission: bad params: %w", err)
	}
	if p.DurableID == "" {
		// The durable-id IS the resource binding; a decommission with no id is unbound — refuse.
		return fmt.Errorf("decommission: op has no durable_id — refusing an unbound decommission")
	}

	// The gate has already verified the operator signature + burned the nonce durably BEFORE this
	// point. This log line is the audit trail of an operator-authorized permanent decommission.
	d.logger.Warn("decommission: executing operator-signed PERMANENT decommission", "durable_id", p.DurableID)
	if err := d.intent.SetDecommissioned(p.DurableID); err != nil {
		return fmt.Errorf("decommission: record intent for %q: %w", p.DurableID, err)
	}
	d.logger.Warn("decommission: operator-signed decommission complete (drive will never auto-mount)", "durable_id", p.DurableID)
	return nil
}