package host

import (
	"context"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"log"
	"os"
	"path/filepath"
	"reflect"
	"time"

	"github.com/carlosframework/platform/internal/hostbox"
	"github.com/carlosframework/platform/internal/hostclaim"
	"github.com/carlosframework/platform/internal/hostguard"
	"github.com/carlosframework/platform/internal/registry"
	"github.com/carlosframework/platform/internal/release"
)

func (h ClaimRootHTTP) commitRootInventory(ctx context.Context, q hostbox.JournalRequest) (hostbox.JournalResponse, error) {
	return h.withRootInventoryHistory(ctx, q, false)
}
func (h ClaimRootHTTP) withRootInventoryHistory(ctx context.Context, q hostbox.JournalRequest, pending bool) (hostbox.JournalResponse, error) {
	if h.history == nil {
		return h.commitRootInventoryPending(ctx, q, pending, nil)
	}
	var out hostbox.JournalResponse
	err := h.history(ctx, func(history *release.RootHistory) error {
		var err error
		out, err = h.commitRootInventoryPending(ctx, q, pending, history)
		return err
	})
	return out, err
}

func (h ClaimRootHTTP) commitRootInventoryPending(ctx context.Context, q hostbox.JournalRequest, pending bool, history *release.RootHistory) (hostbox.JournalResponse, error) {
	var out hostbox.JournalResponse
	if !pending && (q.V == 2 || q.V == 3) {
		now := time.Now()
		if h.Journals != nil && h.Journals.Now != nil {
			now = h.Journals.Now()
		}
		age := now.Sub(time.Unix(0, q.IssuedAt))
		if age > hostbox.JournalRequestWindow || age < -hostbox.JournalRequestWindow {
			return out, hostbox.ErrJournalUncertain
		}
	}
	guard := h.Stop.Coordinator.Guard
	if guard.Root == nil || h.Journals == nil || h.InventoryActor == nil || h.Reconcile.Registry == nil || h.Reconcile.Census == nil {
		return out, hostbox.ErrUnsupported
	}
	if h.RequireNewWork != nil {
		if err := h.RequireNewWork(ctx); err != nil {
			return out, err
		}
	}
	actor, err := h.InventoryActor(ctx)
	if err != nil {
		return out, err
	}
	in, t := q.Inventory, q.Target
	in.Entries = append([]hostbox.StopInventoryEntry(nil), in.Entries...)
	// The inventory's stamp is validated against the fresh binding; a target
	// stamp, when the agent sends one, must name that same binding before
	// any intent is persisted (fix round 1, finding 2).
	if q.Op != "inventory-write" || !in.Complete || in.Box != actor.Box || in.Enrollment != actor.Enrollment || in.DirectoryRevision != actor.Binding || (t.DirectoryRevision != "" && t.DirectoryRevision != in.DirectoryRevision) || t.Host != in.Host || t.Incarnation != in.Incarnation || t.Stamp != in.InstallationStamp || t.Box != actor.Box || t.Enrollment != actor.Enrollment || t.ClaimETag == "" || q.RecordKey == "" || q.RecordETag == "" {
		return out, hostbox.ErrChanged
	}
	observed, err := hostclaim.Read(ctx, h.Stop.Coordinator.Evidence, in.Host)
	if err != nil {
		return out, err
	}
	if observed.Absent || observed.Claim == nil || observed.Claim.Holder == nil {
		return out, hostbox.ErrChanged
	}
	applied := false
	if pending {
		saved, e := h.Journals.Inventory.SnapshotRequest(ctx, t)
		if e != nil {
			return out, e
		}
		applied = saved.Revision == q.Revision+1 && saved.LastRequest == q.ID
	}
	holder := observed.Claim.Holder
	if (!applied && observed.ETag != t.ClaimETag) || holder.Incarnation != t.Incarnation || holder.Stamp != t.Stamp || holder.Session != t.Session || holder.Key != q.RecordKey || observed.Claim.Op.ID != t.Op || observed.Claim.Op.Phase != t.Phase {
		return out, hostbox.ErrChanged
	}
	firstLanding := q.Revision == 0 && observed.Claim.Op.Kind == hostclaim.KindLanding
	if firstLanding {
		if err := rootFirstInstallation(observed.Claim, actor); err != nil {
			return out, err
		}
		entry := rootLandingEntry(q, observed.Claim, actor)
		if len(in.Entries) != 0 {
			return out, hostbox.ErrTypedInventory
		}
		in.Entries = []hostbox.StopInventoryEntry{entry}
	}
	var canonical registry.Route
	var currentRow *registry.Route
	installation := hostguard.RootInstallation{Empty: len(in.Entries) == 0, Host: in.Host, Incarnation: in.Incarnation, Stamp: in.InstallationStamp, Migration: 1, InventoryRevision: q.Revision + 1, Account: holder.Account, App: holder.App, Record: holder.Key, Box: actor.Box, Enrollment: actor.Enrollment}
	if q.Revision == 0 {
		installation.Registration = hostguard.InstallationRegistration{Op: observed.Claim.Op.ID, Kind: observed.Claim.Op.Kind, Phase: observed.Claim.Op.Phase, Session: holder.Session}
		if firstLanding {
			installation.Registration.RowID = in.Entries[0].RowIdentity
		}
	}
	raw, err := json.Marshal(q)
	if err != nil {
		return out, err
	}
	replayed := false
	err = guard.CommitRootInventoryArtifacts(ctx, installation, raw, func(c *hostclaim.Claim) error {
		if !reflect.DeepEqual(c, observed.Claim) {
			return hostbox.ErrChanged
		}
		fresh, err := hostclaim.Read(ctx, h.Stop.Coordinator.Evidence, in.Host)
		if err != nil {
			return err
		}
		if !applied && fresh.ETag != t.ClaimETag {
			return hostbox.ErrChanged
		}
		var etag string
		canonical, etag, err = rootClaimRecord(ctx, h.Stop.Coordinator.Evidence, c, h.Roots["data"])
		if err != nil {
			return err
		}
		if etag != q.RecordETag {
			return hostbox.ErrChanged
		}
		if c.Op.Kind == hostclaim.KindRelocating && q.Revision == 0 {
			rec, e := relocationRecord(ctx, h.Roots["data"], h.Stop.Coordinator.Evidence, observed)
			if e != nil {
				return e
			}
			canonical = rec.Route
		}
		if c.Op.Kind == hostclaim.KindLanding {
			canonical, err = h.rootLandingRoute(ctx, c, actor)
			if err != nil {
				return err
			}
		}
		owner := sha256.Sum256([]byte(fmt.Sprintf("%s\x00%s\x00%d\x00%s", in.Host, in.Incarnation, in.InstallationStamp, actor.Box)))
		canonical.ClaimIncarnation, canonical.ClaimStamp, canonical.ClaimOwner = in.Incarnation, in.InstallationStamp, hex.EncodeToString(owner[:])
		for _, entry := range in.Entries {
			if entry.Kind == "route" {
				if canonical.ClaimRowID != "" {
					return hostbox.ErrTypedInventory
				}
				canonical.ClaimRowID = entry.RowIdentity
			}
		}
		row, err := h.Reconcile.Registry.Get(in.Host)
		if err != nil {
			return err
		}
		currentRow = row
		if row != nil && (row.Host != canonical.Host || row.Account != canonical.Account || row.App != canonical.App || row.DBPath != canonical.DBPath || row.ClaimOwnership != canonical.ClaimOwnership) {
			return hostbox.ErrTypedInventory
		}
		if row == nil {
			for _, e := range in.Entries {
				if e.Kind != "route" || (e.Materialization != "intended" && !firstLanding) {
					return hostbox.ErrTypedInventory
				}
			}
		} else if err := hostbox.ValidateAgentInventory(in, &canonical, h.Roots["data"]); err != nil {
			return err
		}
		if err := h.verifyInventoryTimers(in); err != nil {
			return err
		}
		if err := h.bindInventoryPaths(ctx, &in); err != nil {
			return err
		}
		for _, e := range in.Entries {
			if e.Ownership != canonical.ClaimOwner {
				return hostbox.ErrTypedInventory
			}
			if e.Kind == "route" {
				if e.ManagedRoot != "registry" || e.RelativePath != in.Host || e.RowIdentity == "" {
					return hostbox.ErrTypedInventory
				}
				continue
			}
			if e.Kind == "timer" {
				if err := h.verifyTimerMutationRow(in.Host, canonical.ClaimOwnership, e, q.Timer); err != nil {
					return err
				}
				continue
			}
			if err := h.verifyInventoryPath(e); err != nil {
				return err
			}
		}
		return nil
	}, func(priorRoot hostguard.RootInstallation) error {
		if firstLanding && currentRow != nil && priorRoot.Registration != installation.Registration {
			return hostbox.ErrTypedInventory
		}
		if firstLanding && currentRow == nil && priorRoot.InventoryRevision != 0 {
			return hostbox.ErrTypedInventory
		}
		if observed.Claim.Op.Kind == hostclaim.KindLanding && !firstLanding && !landingRegistrationMatches(priorRoot, observed.Claim, currentRow) {
			return hostbox.ErrTypedInventory
		}

		snapshot, err := h.Journals.Inventory.SnapshotRequest(ctx, hostguard.FenceTarget{Host: in.Host, Incarnation: in.Incarnation, Stamp: in.InstallationStamp})
		prior, revision := snapshot.Inventory, snapshot.Revision
		if err != nil {
			return err
		}
		replay, found, err := h.Journals.Replay(ctx, actor.Box+"/"+actor.Enrollment, q)
		if err != nil {
			return err
		}
		if found {
			if revision != q.Revision+1 || !reflect.DeepEqual(prior, in) {
				return hostbox.ErrChanged
			}
			out = replay
			replayed = true
			return nil
		}
		if revision == q.Revision+1 && reflect.DeepEqual(prior, in) && (priorRoot.InventoryRevision == revision || pending && snapshot.LastRequest == q.ID) {
			out = hostbox.JournalResponse{V: 1, ID: q.ID, Revision: revision}
			replayed = true
			return nil
		}
		if revision != q.Revision {
			return hostbox.ErrChanged
		}
		if err := h.verifyNewInventoryIdentities(prior, in); err != nil {
			return err
		}
		if err := h.verifyTimerMutation(prior, in, q.Timer); err != nil {
			return err
		}
		if revision == 0 {
			if (!firstLanding && len(in.Entries) != 0) || rootFirstInstallation(observed.Claim, actor) != nil {
				return hostbox.ErrChanged
			}
			census := h.rootEmptyCensus()
			selected := hostbox.RecordSelection{Host: in.Host, Key: holder.Key, ETag: q.RecordETag, Incarnation: in.Incarnation, Family: holder.Family}
			if firstLanding && currentRow != nil && priorRoot.Registration == installation.Registration {
				if err := census.CheckRootRegisteredRow(ctx, observed, selected, currentRow.ClaimOwnership); err != nil {
					return err
				}
			} else if err := census.CheckLocal(ctx, observed, selected); err != nil {
				return err
			}
		} else {
			if priorRoot.InventoryRevision != revision {
				return hostbox.ErrChanged
			}
			for _, old := range prior.Entries {
				found := false
				for _, next := range in.Entries {
					if old.ArtifactID == next.ArtifactID {
						if q.Timer != nil && old.Kind == "timer" && old.RelativePath == q.Timer.Timer.Host+"/"+q.Timer.Timer.Name {
							old.RowIdentity, old.Materialization, old.TimerRetired = next.RowIdentity, next.Materialization, next.TimerRetired
						}
						if old.Materialization == "intended" && next.Materialization == "materialized" {
							old.Materialization = next.Materialization
							old.Identity = next.Identity
							old.Device = next.Device
							old.Inode = next.Inode
							old.Type = next.Type
						}
						if old != next {
							return hostbox.ErrChanged
						}
						found = true
					}
				}
				if !found {
					return hostbox.ErrChanged
				}
			}
		}
		return nil
	}, func(prior hostguard.RootInstallation) error {
		if history != nil && q.Revision == 0 && prior.InventoryRevision == 0 && observed.Claim.Op.Kind == hostclaim.KindServing && holder.Session == 0 && holder.WriterBox == "" {
			if err := history.RecordCreation(release.HistoryBinding{Host: in.Host, Account: holder.Account, App: holder.App}, rootHistoryInstallation(installation)); err != nil {
				return err
			}
		}
		if firstLanding && currentRow == nil {
			if err := h.Reconcile.Registry.Upsert(canonical); err != nil {
				return err
			}
		}
		if replayed {
			return nil
		}
		if q.Timer != nil {
			if err := h.applyTimerMutation(*q.Timer); err != nil {
				return err
			}
		}
		if firstLanding || h.inventoryIdentity != nil {
			out, err = h.Journals.ExecuteRootInventory(ctx, actor.Box+"/"+actor.Enrollment, q, in, pending)
		} else if pending {
			out, err = h.Journals.CompletePendingInventory(ctx, actor.Box+"/"+actor.Enrollment, q)
		} else {
			out, err = h.Journals.Execute(ctx, actor.Box+"/"+actor.Enrollment, q)
		}
		return err
	}, func(prior hostguard.RootInstallation) (hostguard.InstallationArtifacts, error) {
		return rootInventoryArtifacts(prior, canonical, in, q.Revision)
	})
	return out, err
}

func (h ClaimRootHTTP) verifyInventoryPath(e hostbox.StopInventoryEntry) error {
	if e.Kind != "path" || e.ManagedRoot != "data" || !filepath.IsLocal(e.RelativePath) {
		return hostbox.ErrTypedInventory
	}
	path := filepath.Join(h.Roots["data"], e.RelativePath)
	if e.Materialization == "intended" {
		if _, err := os.Lstat(path); !errors.Is(err, os.ErrNotExist) {
			return hostbox.ErrChanged
		}
		return nil
	}
	if e.Materialization != "materialized" {
		return hostbox.ErrTypedInventory
	}
	return hostbox.VerifyInventoryIdentity(h.Roots["data"], e)
}

func (h ClaimRootHTTP) verifyNewInventoryIdentities(prior, next hostbox.StopInventory) error {
	for _, e := range next.Entries {
		if e.Kind != "path" || e.Materialization != "materialized" {
			continue
		}
		retained := false
		for _, old := range prior.Entries {
			if old.ArtifactID == e.ArtifactID && old.Materialization == "materialized" {
				retained = true
			}
		}
		if retained {
			continue
		}
		current, err := hostbox.CaptureInventoryIdentity(h.Roots[e.ManagedRoot], e.RelativePath)
		if err != nil {
			return err
		}
		if e.Identity.Boot != current.Boot {
			return hostbox.ErrChanged
		}
		if err := h.verifyInventoryPath(e); err != nil {
			return err
		}
	}
	return nil
}

// obsoleteIntent reports whether a pending intent was stamped under a binding
// other than the startup binding. Its stamp is validated binding evidence
// only: an inventory's own stamp (checked against the fresh binding before
// the intent was persisted) or a rebind's successor stamp (likewise). An
// agent-sent target stamp is never consulted (fix round 1, finding 2).
// Replaying an obsolete intent would compare the old binding with today's
// authority; it is settled instead (N3).
func (h ClaimRootHTTP) obsoleteIntent(stamp string) bool {
	return h.startupBinding != "" && stamp != h.startupBinding
}

// settleObsoleteIntent settles an obsolete pending intent through the
// guard's SettleObsoleteRootInventory (same host lock, exact intent bytes),
// whatever the claim says now: the binding difference alone supersedes it.
// The installation is quarantined and marked settled: it stays refused for
// execution and new work, because every fresh comparison needs the new
// binding, and the migration census at root's next start still inspects it,
// so cleanup and migration startup are not blocked (fix round 1, finding 1).
// applied says whether root's interrupted commit had already landed the
// intent in the inventory; the guard then records the installation that
// commit would have recorded, so guard and inventory agree. A settlement
// failure is logged and leaves the intent pending, as any recovery failure
// does. It never consults InventoryActor, so a quarantined box settles its
// own leftovers.
//
// Cold-handover barriers (roster binding B3) are not pending installations
// and are not settled here: RecoverPending's cold handover recovery settles
// them (hostbox ColdHandover.Obsolete, hostguard
// SettleObsoleteColdHandover) with the same startup binding.
func (h ClaimRootHTTP) settleObsoleteIntent(ctx context.Context, host string, raw []byte, kind, stamped string, applied func(context.Context, hostguard.RootInstallation) (bool, error)) {
	err := h.Stop.Coordinator.Guard.SettleObsoleteRootInventory(ctx, host, raw, applied)
	log.Printf("instance-control: %s: obsolete pending %s intent: stamped %s current %s", host, kind, stamped, h.startupBinding)
	if err != nil {
		log.Printf("instance-control: %s: obsolete pending %s intent not settled: %v", host, kind, err)
	}
}

// inventoryIntentApplied reports whether q, an interrupted inventory write,
// already landed in the inventory: the pending installation's inventory is
// at q's revision and names q as its last request, the test the pending
// replay makes (commitRootInventoryPending's applied).
func (h ClaimRootHTTP) inventoryIntentApplied(q hostbox.JournalRequest) func(context.Context, hostguard.RootInstallation) (bool, error) {
	return func(ctx context.Context, pending hostguard.RootInstallation) (bool, error) {
		if h.Journals == nil || h.Journals.Inventory == nil {
			return false, hostbox.ErrUnsupported
		}
		saved, err := h.Journals.Inventory.SnapshotRequest(ctx, hostguard.FenceTarget{Host: pending.Host, Incarnation: pending.Incarnation, Stamp: pending.Stamp})
		if err != nil {
			return false, err
		}
		return saved.Revision == q.Revision+1 && saved.LastRequest == q.ID && saved.Revision == pending.InventoryRevision, nil
	}
}

// rebindIntentUnapplied: a recovery rebind's commit writes only the
// successor's inventory, so the predecessor the record keeps still agrees
// with its own inventory; the record keeps it.
func rebindIntentUnapplied(context.Context, hostguard.RootInstallation) (bool, error) {
	return false, nil
}

func (h ClaimRootHTTP) recoverRootInventory(ctx context.Context) error {
	authority := h.Stop.Coordinator.Guard.Root
	if authority == nil {
		return nil
	}
	pending, err := authority.PendingInstallations()
	if err != nil {
		return err
	}
	for _, raw := range pending {
		var recovery recoveryRebindIntent
		if err = json.Unmarshal(raw, &recovery); err != nil {
			return err
		}
		if recovery.Recovery != nil {
			if next := recovery.Recovery.Next; h.obsoleteIntent(next.DirectoryRevision) {
				h.settleObsoleteIntent(ctx, next.Host, raw, "rebind", next.DirectoryRevision, rebindIntentUnapplied)
				continue
			}
			if err = h.rebindRecoveryInventory(ctx, *recovery.Recovery); err != nil {
				n := recovery.Recovery.Next
				if errors.Is(err, hostbox.ErrChanged) {
					err = errors.Join(err, h.Stop.Coordinator.Guard.AbandonRootInventory(ctx, n.Host, raw, func(c *hostclaim.Claim) bool {
						fresh, e := hostclaim.Read(ctx, h.Stop.Coordinator.Evidence, n.Host)
						return e == nil && fresh.Claim != nil && reflect.DeepEqual(c, fresh.Claim) && fresh.ETag != n.ETag
					}, rebindIntentUnapplied))
				}
				log.Printf("instance-control: %s: %v", n.Host, err)
			}
			continue
		}
		var q hostbox.JournalRequest
		if err = json.Unmarshal(raw, &q); err != nil {
			return err
		}
		if settled, settleErr := h.settleTimerInventory(ctx, q, raw); settled {
			continue
		} else if settleErr != nil {
			return settleErr
		}
		if h.obsoleteIntent(q.Inventory.DirectoryRevision) {
			h.settleObsoleteIntent(ctx, q.Target.Host, raw, "inventory", q.Inventory.DirectoryRevision, h.inventoryIntentApplied(q))
			continue
		}
		if _, err = h.withRootInventoryHistory(ctx, q, true); err != nil {
			if errors.Is(err, hostbox.ErrChanged) || errors.Is(err, hostbox.ErrJournalUncertain) {
				err = errors.Join(err, h.Stop.Coordinator.Guard.AbandonRootInventory(ctx, q.Target.Host, raw, func(c *hostclaim.Claim) bool {
					fresh, readErr := hostclaim.Read(ctx, h.Stop.Coordinator.Evidence, q.Target.Host)
					if readErr != nil || fresh.Claim == nil || !reflect.DeepEqual(c, fresh.Claim) {
						return false
					}
					_, recordETag, recordErr := h.Stop.Coordinator.Evidence.Get(ctx, q.RecordKey)
					return recordErr == nil && recordETag != q.RecordETag || fresh.ETag != q.Target.ClaimETag || c.Holder == nil || c.Holder.Incarnation != q.Target.Incarnation || c.Holder.Stamp != q.Target.Stamp || c.Holder.Session != q.Target.Session || c.Op.ID != q.Target.Op || c.Op.Phase != q.Target.Phase || errors.Is(err, hostbox.ErrJournalUncertain)
				}, h.inventoryIntentApplied(q)))
			}
			log.Printf("instance-control: %s: %v", q.Target.Host, err)
		}
	}
	return nil
}