package host

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"io"
	"os"
	"path/filepath"
	"reflect"
	"sort"
	"strings"

	"github.com/carlosframework/platform/internal/hostbox"
	"github.com/carlosframework/platform/internal/rootstate"
)

// A completed root retirement changes where an obligation is checked. It never
// deletes the payload, its requirements, or a generation reservation.
func generationRetirements(ctx context.Context, snapshot generationInventory) (map[int]string, error) {
	transfers, err := generationTransfers(ctx, snapshot)
	if err != nil {
		return nil, err
	}
	retired := map[int]string{}
	for _, j := range snapshot.Retirements {
		if err := ctx.Err(); err != nil {
			return nil, err
		}
		canonical, err := hostbox.NewRetirementJournal(j.ID, j.Inventory)
		if err != nil || j.V != 1 || !j.Complete || j.Target == nil || j.ID != j.Target.FenceID || !reflect.DeepEqual(j.Inventory, canonical.Inventory) || len(j.Steps) != len(canonical.Steps) {
			return nil, os.ErrPermission
		}
		for i, step := range j.Steps {
			if !step.Done || step.Artifact != canonical.Steps[i].Artifact {
				return nil, os.ErrPermission
			}
		}
		t := *j.Target
		if t.Incarnation == "." || t.Incarnation == ".." || strings.ContainsAny(t.Incarnation, "/\\\x00") {
			return nil, os.ErrPermission
		}
		index := -1
		for i, p := range snapshot.Payloads {
			in := p.Inventory
			if in.Host == t.Host && in.Incarnation == t.Incarnation && in.InstallationStamp == t.Stamp {
				if index != -1 || in.Box != t.Box || in.Enrollment != t.Enrollment || in.DirectoryRevision != t.DirectoryRevision {
					return nil, os.ErrPermission
				}
				index = i
			}
		}
		if index < 0 || retired[index] != "" || j.Inventory.Host != t.Host || j.Inventory.Captured.Incarnation != t.Incarnation || j.Inventory.Captured.Stamp != t.Stamp {
			return nil, os.ErrPermission
		}
		receipt := false
		for _, view := range snapshot.Installations {
			if view.Host != t.Host {
				continue
			}
			for _, r := range view.Receipts {
				if r.Target == t && bytes.Equal(r.Bytes, j.StopReceipt) && verifyRetirementReceipt(ctx, r) == nil {
					receipt = true
				}
			}
		}
		if !receipt {
			return nil, os.ErrPermission
		}
		expected := map[hostbox.Artifact]bool{}
		for _, e := range snapshot.Payloads[index].Inventory.Entries {
			if e.Ownership != j.Inventory.Ownership || (e.Materialization != "materialized" && !(e.Kind == "timer" && e.Materialization == "intended")) {
				return nil, os.ErrPermission
			}
			a := hostbox.Artifact{AllowAbsent: e.Kind == "timer" && (e.TimerRetired || e.Materialization == "intended"), Kind: hostbox.ArtifactKind(e.Kind), Root: e.ManagedRoot, Name: e.RelativePath, Owner: e.Ownership, RowID: e.RowIdentity, Identity: e.Identity, Dev: e.Device, Ino: e.Inode, Type: e.Type}
			if expected[a] {
				return nil, os.ErrPermission
			}
			expected[a] = true
		}
		matched := map[hostbox.Artifact]bool{}
		for _, a := range j.Inventory.Artifacts {
			// The retirement producer also captures the timer registration. Root's
			// inventory establishes that registration as the timer's exact row ID.
			if a.Kind == hostbox.ArtifactTimer {
				row, registration, ok := strings.Cut(a.RowID, "~")
				if ok {
					if row != registration {
						return nil, os.ErrPermission
					}
					a.RowID = row
				}
			}
			if !expected[a] {
				return nil, os.ErrPermission
			}
			matched[a] = true
		}
		if len(matched) != len(expected) {
			return nil, os.ErrPermission
		}
		retired[index] = j.ID
	}
	for prior := range transfers {
		next := prior
		for steps := 0; ; steps++ {
			if steps > len(transfers) {
				return nil, os.ErrPermission
			}
			successor, ok := transfers[next]
			if !ok {
				break
			}
			next = successor
		}
		if id := retired[next]; id != "" {
			if retired[prior] != "" {
				return nil, os.ErrPermission
			}
			retired[prior] = id
		}
	}
	return retired, nil
}

func generationPhysicalPayloads(ctx context.Context, snapshot generationInventory) ([]hostbox.GenerationPayload, error) {
	retired, err := generationRetirements(ctx, snapshot)
	if err != nil {
		return nil, err
	}
	for i, payload := range snapshot.Payloads {
		if retired[i] != "" {
			continue
		}
		for _, entry := range payload.Inventory.Entries {
			if entry.Materialization != "materialized" {
				return nil, os.ErrPermission
			}
		}
	}
	payloads := append([]hostbox.GenerationPayload(nil), snapshot.Payloads...)
	transfers, err := generationTransfers(ctx, snapshot)
	if err != nil {
		return nil, err
	}
	for prior := range transfers {
		next := transfers[prior]
		for steps := 0; ; steps++ {
			if steps > len(transfers) {
				return nil, os.ErrPermission
			}
			successor, ok := transfers[next]
			if !ok {
				break
			}
			next = successor
		}
		in := &payloads[prior].Inventory
		in.Entries = append([]hostbox.StopInventoryEntry(nil), in.Entries...)
		for i, entry := range in.Entries {
			if entry.Kind != "path" {
				continue
			}
			for _, current := range snapshot.Payloads[next].Inventory.Entries {
				if current.Kind == "path" && current.ManagedRoot == entry.ManagedRoot && current.RelativePath == entry.RelativePath {
					in.Entries[i].Identity, in.Entries[i].Device = current.Identity, current.Device
				}
			}
		}
	}
	for i, id := range retired {
		in := &payloads[i].Inventory
		in.Entries = append([]hostbox.StopInventoryEntry(nil), in.Entries...)
		for n, e := range in.Entries {
			if e.Kind == "path" {
				if !filepath.IsLocal(e.RelativePath) || filepath.Clean(e.RelativePath) != e.RelativePath {
					return nil, os.ErrPermission
				}
				roots := map[string]string{"data": dataDir()}
				parker := hostbox.TypedParker{CapturePersistent: true, Roots: roots, ParkedRoots: roots}
				parkRoot, err := parker.ParkedArtifactRoot(hostbox.Artifact{Root: e.ManagedRoot, Name: e.RelativePath, Identity: e.Identity})
				if err != nil {
					return nil, err
				}
				rel, err := filepath.Rel(dataDir(), parkRoot)
				if err != nil || !filepath.IsLocal(rel) {
					return nil, os.ErrPermission
				}
				in.Entries[n].RelativePath = filepath.Join(rel, ".parked", in.Incarnation, in.Host, id, e.ManagedRoot, e.RelativePath)
			}
		}
	}
	return payloads, nil
}

func generationRetirementRecords(ctx context.Context, store rootstate.Store) ([]hostbox.RetirementJournal, error) {
	names, err := store.Names()
	if err != nil {
		return nil, err
	}
	if len(names) > 8192 {
		return nil, os.ErrPermission
	}
	sort.Strings(names)
	var out []hostbox.RetirementJournal
	for _, name := range names {
		if err := ctx.Err(); err != nil {
			return nil, err
		}
		// Cold handover retains its own payload inventory. It is never parking
		// authority here. Temporary writes cannot establish completed retirement.
		if name == "cold" || name == "serving" || strings.HasPrefix(name, ".retire-") {
			continue
		}
		if !strings.HasSuffix(name, ".json") {
			return nil, os.ErrPermission
		}
		raw, err := store.Read(name)
		if err != nil {
			return nil, err
		}
		var j hostbox.RetirementJournal
		dec := json.NewDecoder(bytes.NewReader(raw))
		dec.DisallowUnknownFields()
		if dec.Decode(&j) != nil || dec.Decode(new(any)) != io.EOF || j.ID+".json" != name {
			return nil, os.ErrPermission
		}
		out = append(out, j)
	}
	return out, nil
}

func productionGenerationRetirements(ctx context.Context) ([]hostbox.RetirementJournal, error) {
	return generationReadRetirements(ctx, claimRetireJournalDir("", ""), func(path string) (rootstate.Store, error) {
		return rootstate.Open(path, false, false)
	}, func(path string) error {
		directory, err := os.Open(path)
		if err != nil {
			return err
		}
		defer directory.Close()
		return directory.Sync()
	})
}

func generationReadRetirements(ctx context.Context, path string, open func(string) (rootstate.Store, error), sync func(string) error) ([]hostbox.RetirementJournal, error) {
	store, err := open(path)
	if errors.Is(err, os.ErrNotExist) {
		return nil, nil
	}
	if err != nil {
		return nil, err
	}
	defer store.Close()
	journals, err := generationRetirementRecords(ctx, store)
	if err != nil {
		return nil, err
	}
	// Sync the completion rename without rewriting concurrent progress.
	if err := sync(path); err != nil {
		return nil, err
	}
	return journals, nil
}