package web

// PBS DR tier (SLICE 1): the hub-side provisioning flow behind the customer config form's
// "PBS DR tier (ep0)" section. On enable+save: verify the host's WG peer exists (the agent
// self-registers its pubkey — absence is fail-closed, nothing to allocate here) → provision the
// per-customer ep0 tenancy over the tenantsync channel → store the token secret CONSUME-ONCE
// (host-scoped; the agent fetches it via POST /api/v1/hosts/{id}/pbs/consume-token) → merge the
// NON-SECRET descriptor into the host's desired_json under "pbs_dr" (the admin-set path;
// SetHostDesired bumps the generation, which is the agent's change signal).
//
// Fail-closed like applyOffsite: any error means NO descriptor write, NO bump, NO half-enabled
// state. Idempotent: an already-provisioned descriptor short-circuits — no tenantsync call, no
// second secret, no spurious bump. Disable rewrites the descriptor with enabled=false (bump) —
// the ep0 namespace/token are NOT deprovisioned (the offsite-disable precedent: data deletion is
// a deliberate, separate decision).

import (
	"context"
	"database/sql"
	"encoding/json"
	"errors"
	"fmt"
	"net/http"
	"regexp"
	"strings"
	"time"

	"gitea.dooplex.hu/admin/felhom-hub/internal/store"
	"gitea.dooplex.hu/admin/felhom-hub/internal/tenantsync"
)

// tenancyProvisioner is the tenantsync seam — satisfied by *tenantsync.Client; tests inject a fake.
type tenancyProvisioner interface {
	Provision(ctx context.Context, customerID string) (*tenantsync.Result, error)
	Reissue(ctx context.Context, customerID string) (*tenantsync.Result, error)
}

// SetTenantSync enables PBS DR tier provisioning (optional). Without it, saving a config with the
// tier enabled returns an error (not configured on this hub); the form section still renders.
func (s *Server) SetTenantSync(p tenancyProvisioner) { s.tenantsync = p }

// pbsDRDescriptor is the NON-SECRET pbs_dr block in a host's desired_json. It NEVER carries the
// token secret (that is host_pbs_secrets custody, consume-once).
type pbsDRDescriptor struct {
	Enabled     bool   `json:"enabled"`
	StorageID   string `json:"storage_id,omitempty"`
	PBSTunnelIP string `json:"pbs_tunnel_ip,omitempty"`
	Datastore   string `json:"datastore,omitempty"`
	Namespace   string `json:"namespace,omitempty"`
	TokenID     string `json:"token_id,omitempty"`
	Fingerprint string `json:"fingerprint,omitempty"`
}

// defaultPBSStorageID is the storage-entry id the agent bridge creates on a customer box. The DEMO
// host's adopted manual entry is `felhom-offsite` — the descriptor carries the id so the bridge is
// name-agnostic and the felhom-pbs collision on the demo dissolves (spike naming note).
const defaultPBSStorageID = "felhom-pbs"

// pveStorageIDRe validates the operator-typed storage id (PVE storage-id grammar, conservative).
var pveStorageIDRe = regexp.MustCompile(`^[A-Za-z][A-Za-z0-9_.-]{0,27}$`)

// readPBSDR extracts the pbs_dr descriptor from a host's desired_json ("" / absent → nil).
func readPBSDR(desiredJSON string) *pbsDRDescriptor {
	var doc struct {
		PBSDR *pbsDRDescriptor `json:"pbs_dr"`
	}
	if err := json.Unmarshal([]byte(desiredJSON), &doc); err != nil {
		return nil
	}
	return doc.PBSDR
}

// mergePBSDR merges the descriptor under the "pbs_dr" key of a desired_json object, preserving
// every other key (the operator blob, dr blocks…). Same shape as offsite.MergeDescriptor.
func mergePBSDR(desiredJSON string, d *pbsDRDescriptor) (string, error) {
	obj := map[string]json.RawMessage{}
	if strings.TrimSpace(desiredJSON) != "" && desiredJSON != "{}" {
		if err := json.Unmarshal([]byte(desiredJSON), &obj); err != nil {
			return "", fmt.Errorf("pbsdr: parse desired_json: %w", err)
		}
	}
	db, err := json.Marshal(d)
	if err != nil {
		return "", err
	}
	obj["pbs_dr"] = db
	out, err := json.Marshal(obj)
	if err != nil {
		return "", err
	}
	return string(out), nil
}

// applyPBSDR handles the config form's DR-tier section on create/update. Called BEFORE
// SaveCustomerConfig (fail-closed on REAL provisioning failures: those abort the whole save).
// The descriptor lives in the HOST's desired_json — ConfigJSON never carries pbs_dr.
//
// v0.51.0 (DR-tier-by-default): the switch is cfg.DRTier (the stored per-customer flag, set from
// the form by the handler) — and an UNMET PRECONDITION is no longer an error. New customers
// default the flag ON before any host exists; the cascade converges later: host enrolls → WG
// peer registers (the api hook auto-provisions, scenario A) → descriptor applies on the agent's
// next tick. The form save stores the intent and reports the honest waiting stage; only an
// actual provisioning FAILURE (tenantsync error, token mismatch…) still fails the save.
func (s *Server) applyPBSDR(ctx context.Context, r *http.Request, cfg *store.CustomerConfig) error {
	enabled := cfg.DRTier
	storageID := strings.TrimSpace(r.FormValue("pbsdr_storage_id"))
	if storageID == "" {
		storageID = defaultPBSStorageID
	}

	host, err := s.store.GetHostByCustomer(cfg.CustomerID)
	if err != nil {
		return fmt.Errorf("pbsdr: host lookup: %w", err)
	}
	if host == nil {
		if enabled {
			s.logger.Printf("[INFO] pbsdr: DR tier ON for %s, no host enrolled yet — the descriptor applies once the cascade is ready (host → WG peer → apply)", cfg.CustomerID)
		}
		return nil // the flag is stored; nothing host-side to converge yet
	}
	cur := readPBSDR(host.DesiredJSON)

	if !enabled {
		// Disable = descriptor enabled:false (coords kept; NO ep0 deprovision). Only when there is
		// something to disable — otherwise a pure no-op (no spurious bump).
		if cur == nil || !cur.Enabled {
			return nil
		}
		cur.Enabled = false
		merged, err := mergePBSDR(host.DesiredJSON, cur)
		if err != nil {
			return err
		}
		gen, err := s.store.SetHostDesired(host.HostID, []byte(merged))
		if err != nil {
			return fmt.Errorf("pbsdr: desired-state write: %w", err)
		}
		s.logger.Printf("[INFO] pbsdr disabled for %s (host %s, gen %d; ep0 tenancy kept)", cfg.CustomerID, host.HostID, gen)
		return nil
	}

	if !pveStorageIDRe.MatchString(storageID) {
		return fmt.Errorf("invalid PBS storage id %q", storageID)
	}

	// Already provisioned → success-no-op (descriptor re-served unchanged; NO new secret, no
	// tenantsync call). Only an actual change (re-enable, storage id edit) rewrites + bumps.
	if cur != nil && cur.Namespace != "" {
		if cur.Enabled && cur.StorageID == storageID {
			return nil
		}
		cur.Enabled = true
		cur.StorageID = storageID
		merged, err := mergePBSDR(host.DesiredJSON, cur)
		if err != nil {
			return err
		}
		gen, err := s.store.SetHostDesired(host.HostID, []byte(merged))
		if err != nil {
			return fmt.Errorf("pbsdr: desired-state write: %w", err)
		}
		s.logger.Printf("[INFO] pbsdr descriptor updated for %s (host %s, gen %d; tenancy unchanged)", cfg.CustomerID, host.HostID, gen)
		return nil
	}

	// Fresh provision — the shared atom (also fired by the WG-registration hook, scenario A).
	// An unmet precondition is an honest waiting stage, never a save-blocking error.
	blocked, err := s.pbsdrProvisionAtom(ctx, cfg.CustomerID, host, storageID)
	if err != nil {
		return err
	}
	if blocked != "" {
		s.logger.Printf("[INFO] pbsdr: DR tier ON for %s — waiting: %s", cfg.CustomerID, blocked)
	}
	return nil
}

// pbsdrProvisionAtom runs the fresh-provision cascade step for a host with NO provisioned
// descriptor yet: preconditions → tenantsync provision → consume-once secret → descriptor merge
// + generation bump. Returns (blockedReason, err): a non-empty blockedReason is an HONEST
// waiting stage (tunnel peer absent, endpoint unset, tenantsync unconfigured — the cascade
// retries at its next opportunity); err is a REAL provisioning failure and must stay loud
// (fail-closed on the form path, error-logged on the hook path).
func (s *Server) pbsdrProvisionAtom(ctx context.Context, customerID string, host *store.Host, storageID string) (string, error) {
	if s.tenantsync == nil {
		return "PBS DR provisioning is not configured on this hub (no tenantsync key)", nil
	}
	if _, err := s.store.GetWGPeerForHost(host.HostID); err == sql.ErrNoRows {
		return fmt.Sprintf("host %s has not reported a WG key yet — the tunnel peer must exist before the PBS DR tier", host.HostID), nil
	} else if err != nil {
		return "", fmt.Errorf("pbsdr: wg peer lookup: %w", err)
	}
	ep, err := s.store.GetWGEndpoint()
	if err == sql.ErrNoRows {
		return "wg endpoint not configured — register ep0 before the PBS DR tier", nil
	} else if err != nil {
		return "", fmt.Errorf("pbsdr: wg endpoint read: %w", err)
	}

	// Detach from the request context (the applyOffsite F1 precedent): once provisioning starts,
	// provision→store-secret→descriptor must complete; an impatient re-click must not cancel
	// between the ep0 mutation and the consume-once store write (a stranded token would need a
	// manual re-issue). The absolute timeout still bounds a hung SSH exec.
	ctx, cancel := context.WithTimeout(context.WithoutCancel(ctx), 2*time.Minute)
	defer cancel()
	res, err := s.tenantsync.Provision(ctx, customerID)
	if errors.Is(err, tenantsync.ErrTokenExists) {
		// ep0 has a token but the hub has no descriptor — state mismatch (lost hub state or a
		// half-torn earlier attempt). Never silently re-key: the operator decides via Re-issue.
		return "", fmt.Errorf("the endpoint already holds a PBS token for %s but the hub has no descriptor — use the explicit \"Re-issue PBS credentials\" action", customerID)
	}
	if err != nil {
		return "", err
	}

	// The atom: secret first (consume-once custody), then descriptor+bump (the agent's signal).
	if err := s.store.SaveHostPBSSecret(host.HostID, res.TokenSecret); err != nil {
		return "", fmt.Errorf("pbsdr: store one-time token secret: %w", err)
	}
	desc := &pbsDRDescriptor{
		Enabled:     true,
		StorageID:   storageID,
		PBSTunnelIP: ep.PBSTunnelIP,
		Datastore:   res.Datastore,
		Namespace:   res.Namespace,
		TokenID:     res.TokenID,
		Fingerprint: res.Fingerprint,
	}
	merged, err := mergePBSDR(host.DesiredJSON, desc)
	if err != nil {
		return "", err
	}
	gen, err := s.store.SetHostDesired(host.HostID, []byte(merged))
	if err != nil {
		return "", fmt.Errorf("pbsdr: desired-state write: %w", err)
	}
	s.logger.Printf("[INFO] pbsdr provisioned for %s (host %s, ns %s, token_id %s, gen %d; secret stored consume-once, withheld from logs)",
		customerID, host.HostID, res.Namespace, res.TokenID, gen)
	return "", nil
}

// PBSDRAutoProvision is the WG-registration hook (v0.51.0, scenario A): the api handler calls it
// (via the main.go closure) right after a host's first WG peer registration. If the customer's
// DR-tier flag is ON and no descriptor is provisioned yet, it runs the provisioning atom — the
// descriptor then applies on the agent's next desired-state tick with ZERO operator steps.
// Never fails the caller: outcomes are logged (an error here is retried by the next config save).
func (s *Server) PBSDRAutoProvision(ctx context.Context, customerID string) {
	cfg, err := s.store.GetCustomerConfig(customerID)
	if err != nil || cfg == nil || !cfg.DRTier {
		return
	}
	host, err := s.store.GetHostByCustomer(customerID)
	if err != nil || host == nil {
		return
	}
	if cur := readPBSDR(host.DesiredJSON); cur != nil && cur.Namespace != "" {
		return // already provisioned — nothing to converge here
	}
	storageID := defaultPBSStorageID
	if cur := readPBSDR(host.DesiredJSON); cur != nil && cur.StorageID != "" {
		storageID = cur.StorageID
	}
	blocked, err := s.pbsdrProvisionAtom(ctx, customerID, host, storageID)
	if err != nil {
		s.logger.Printf("[ERROR] pbsdr auto-provision for %s (WG-registration hook): %v — save the customer config to retry", customerID, err)
		return
	}
	if blocked != "" {
		s.logger.Printf("[INFO] pbsdr auto-provision for %s still waiting: %s", customerID, blocked)
		return
	}
	s.logger.Printf("[INFO] pbsdr auto-provisioned for %s on WG registration (hands-free cascade)", customerID)
}

// handlePBSDRReissue explicitly re-keys the customer's ep0 PBS token (the offsite F4 precedent):
// tenantsync reissue → fresh consume-once secret → descriptor refresh + generation bump so the
// agent re-runs its bridge and consumes the fresh secret. The secret value is never logged.
func (s *Server) handlePBSDRReissue(w http.ResponseWriter, r *http.Request, customerID string) {
	if s.tenantsync == nil {
		http.Error(w, "PBS DR provisioning is not configured on this hub", http.StatusBadGateway)
		return
	}
	cfg, err := s.store.GetCustomerConfig(customerID)
	if err != nil || cfg == nil {
		http.NotFound(w, r)
		return
	}
	host, err := s.store.GetHostByCustomer(customerID)
	if err != nil || host == nil {
		http.Error(w, "No host enrolled for this customer", http.StatusBadRequest)
		return
	}
	cur := readPBSDR(host.DesiredJSON)
	if cur == nil || cur.Namespace == "" {
		http.Error(w, "No provisioned PBS DR tier for this customer", http.StatusBadRequest)
		return
	}

	// Same detached-ctx discipline as applyPBSDR: reissue→store→bump is the atom.
	ctx, cancel := context.WithTimeout(context.WithoutCancel(r.Context()), 2*time.Minute)
	defer cancel()
	res, err := s.tenantsync.Reissue(ctx, customerID)
	if err != nil {
		s.logger.Printf("[ERROR] pbsdr reissue for %s: %v", customerID, err)
		http.Error(w, "PBS credential re-issue failed: "+err.Error(), http.StatusBadGateway)
		return
	}
	if err := s.store.SaveHostPBSSecret(host.HostID, res.TokenSecret); err != nil {
		s.logger.Printf("[ERROR] pbsdr reissue for %s: secret store: %v", customerID, err)
		http.Error(w, "Re-issued on the endpoint but storing the secret failed — re-issue again", http.StatusInternalServerError)
		return
	}
	cur.TokenID = res.TokenID
	cur.Fingerprint = res.Fingerprint
	cur.Datastore = res.Datastore
	cur.Namespace = res.Namespace
	merged, err := mergePBSDR(host.DesiredJSON, cur)
	if err == nil {
		_, err = s.store.SetHostDesired(host.HostID, []byte(merged))
	}
	if err != nil {
		s.logger.Printf("[ERROR] pbsdr reissue for %s: descriptor bump: %v", customerID, err)
		http.Error(w, "Credential re-issued but the descriptor bump failed — save the config once to trigger the pickup", http.StatusInternalServerError)
		return
	}
	s.logger.Printf("[INFO] pbsdr credentials re-issued for %s (host %s; fresh consume-once secret stored)", customerID, host.HostID)
	http.Redirect(w, r, "/customers/"+customerID+"?flash=pbsdr_reissued#tab=edit", http.StatusSeeOther)
}

// pbsDRView is the config form's render model for the DR-tier section, including the v0.51.0
// cascade stages (host → WG peer → descriptor → escrow) — one flag, ordered rollout, honest
// intermediate states (scenario D).
type pbsDRView struct {
	Supported     bool   // tenantsync configured on this hub
	NoHost        bool   // no enrolled host for the customer (cascade stage 1 waiting)
	HostID        string
	DRTier        bool   // the stored per-customer flag (operator INTENT)
	Enabled       bool   // descriptor enabled (host-side reality)
	StorageID     string // current or the default
	Provisioned   bool
	Namespace     string
	TokenID       string
	WGPeer        bool // cascade stage 2: the host has registered its tunnel peer
	EscrowPresent bool // cascade stage 4: the ceremony ran (blob in custody)
}

// pbsDRViewFor loads the section state for the form. Read-only; every error degrades to a
// zero-ish view (the section still renders). drTier is the customer's stored flag (the caller
// has the config; "" customerID = the create form).
func (s *Server) pbsDRViewFor(customerID string, drTier bool) pbsDRView {
	v := pbsDRView{Supported: s.tenantsync != nil, StorageID: defaultPBSStorageID, DRTier: drTier}
	if customerID == "" {
		v.NoHost = true
		return v
	}
	host, err := s.store.GetHostByCustomer(customerID)
	if err != nil || host == nil {
		v.NoHost = true
		return v
	}
	v.HostID = host.HostID
	if _, err := s.store.GetWGPeerForHost(host.HostID); err == nil {
		v.WGPeer = true
	}
	if escrow, err := s.store.GetHostEscrow(host.HostID); err == nil && escrow != nil {
		v.EscrowPresent = true
	}
	if d := readPBSDR(host.DesiredJSON); d != nil {
		v.Enabled = d.Enabled
		if d.StorageID != "" {
			v.StorageID = d.StorageID
		}
		v.Provisioned = d.Namespace != ""
		v.Namespace = d.Namespace
		v.TokenID = d.TokenID
	}
	return v
}