// Package restorespace is the production seam behind reconcile.RestoreSpace (R-672, agent v0.133.0):
// how much a restore of an archive writes, how much a storage has free, and which storages a
// restore-test may target. Every read that cannot answer returns an error — the preflight then
// REFUSES (reconcile/restoretest_space.go rule 3); nothing here guesses.
package restorespace

import (
	"context"
	"fmt"
	"os"
	"path"
	"regexp"
	"strconv"
	"strings"

	"gitea.dooplex.hu/admin/felhom-agent/internal/proxmox"
	"gitea.dooplex.hu/admin/felhom-agent/internal/reconcile"
)

// API is the Proxmox subset the provider reads.
type API interface {
	ListStorage(ctx context.Context) ([]proxmox.Storage, error)
	NodeStorage(ctx context.Context) ([]proxmox.Storage, error)
	StorageContent(ctx context.Context, store string) ([]proxmox.StorageContent, error)
	Permissions(ctx context.Context, aclPath string) (map[string]int, error)
}

// Provider implements reconcile.RestoreSpace.
type Provider struct {
	API API
	// ThinMeta reads a thin pool's metadata-used fraction (storage.HostOps.ThinPoolMetadata).
	ThinMeta func(ctx context.Context, vg, pool string) (float64, bool)
	// ReadFile reads a vzdump log; nil → os.ReadFile.
	ReadFile func(name string) ([]byte, error)
}

var _ reconcile.RestoreSpace = (*Provider)(nil)

// totalWrittenRe is vzdump's own count of the bytes tar wrote into the archive — the UNCOMPRESSED size,
// i.e. what a restore writes back ("INFO: Total bytes written: 22607360000 (22GiB, 49MiB/s)").
var totalWrittenRe = regexp.MustCompile(`Total bytes written:\s*(\d+)`)

// archiveExts are the vzdump archive suffixes; the log is the archive name without it + ".log".
var archiveExts = []string{".tar.zst", ".tar.gz", ".tar.lzo", ".tgz", ".tar"}

func (p *Provider) readFile(name string) ([]byte, error) {
	if p.ReadFile != nil {
		return p.ReadFile(name)
	}
	return os.ReadFile(name)
}

// RestoredBytes: a file-backed archive → its vzdump log's "Total bytes written"; a PBS archive → the
// size Proxmox reports for the snapshot (its logical, uncompressed size). The archive FILE size is never
// used: it is compressed (6.9 GB for a 22.6 GB restore, measured 2026-09-24).
func (p *Provider) RestoredBytes(ctx context.Context, archive string) (int64, string, error) {
	id, vol, ok := strings.Cut(archive, ":")
	if !ok || id == "" || vol == "" {
		return 0, "", fmt.Errorf("not a storage volid: %q", archive)
	}
	st, err := p.storageConfig(ctx, id)
	if err != nil {
		return 0, "", err
	}
	switch st.Type {
	case "pbs":
		items, err := p.API.StorageContent(ctx, id)
		if err != nil {
			return 0, "", fmt.Errorf("list %s: %w", id, err)
		}
		for _, it := range items {
			if it.VolID == archive && it.Size > 0 {
				return it.Size, "pbs snapshot size", nil
			}
		}
		return 0, "", fmt.Errorf("archive %s not listed on %s with a size", archive, id)
	default:
		if st.Path == "" {
			return 0, "", fmt.Errorf("storage %s (%s) has no path to read a vzdump log from", id, st.Type)
		}
		base := path.Base(vol) // "backup/vzdump-lxc-…tar.zst" → "vzdump-lxc-…tar.zst"
		stem := ""
		for _, ext := range archiveExts {
			if strings.HasSuffix(base, ext) {
				stem = strings.TrimSuffix(base, ext)
				break
			}
		}
		if stem == "" {
			return 0, "", fmt.Errorf("unknown archive suffix: %s", base)
		}
		logPath := path.Join(st.Path, "dump", stem+".log")
		b, err := p.readFile(logPath)
		if err != nil {
			return 0, "", fmt.Errorf("read vzdump log %s: %w", logPath, err)
		}
		m := totalWrittenRe.FindSubmatch(b)
		if m == nil {
			return 0, "", fmt.Errorf("vzdump log %s carries no \"Total bytes written\"", logPath)
		}
		n, err := strconv.ParseInt(string(m[1]), 10, 64)
		if err != nil || n <= 0 {
			return 0, "", fmt.Errorf("vzdump log %s: bad byte count %q", logPath, m[1])
		}
		return n, "vzdump log: total bytes written", nil
	}
}

func (p *Provider) storageConfig(ctx context.Context, id string) (proxmox.Storage, error) {
	all, err := p.API.ListStorage(ctx)
	if err != nil {
		return proxmox.Storage{}, fmt.Errorf("list storage config: %w", err)
	}
	for _, s := range all {
		if s.Storage == id {
			return s, nil
		}
	}
	return proxmox.Storage{}, fmt.Errorf("storage %s not configured", id)
}

// Free reads the node's live usage for `storage`; a thin pool adds its metadata fill.
func (p *Provider) Free(ctx context.Context, storage string) (reconcile.StorageFree, error) {
	live, err := p.API.NodeStorage(ctx)
	if err != nil {
		return reconcile.StorageFree{}, fmt.Errorf("node storage: %w", err)
	}
	for _, s := range live {
		if s.Storage != storage {
			continue
		}
		if s.Active != 1 {
			return reconcile.StorageFree{}, fmt.Errorf("storage %s is not active", storage)
		}
		fr := reconcile.StorageFree{AvailBytes: s.Avail, UsedBytes: s.Used, Thin: s.Type == "lvmthin"}
		if fr.Thin {
			cfg, cerr := p.storageConfig(ctx, storage)
			if cerr == nil && p.ThinMeta != nil && cfg.VGName != "" && cfg.ThinPool != "" {
				fr.MetaUsedFraction, fr.MetaKnown = p.ThinMeta(ctx, cfg.VGName, cfg.ThinPool)
			}
		}
		return fr, nil
	}
	return reconcile.StorageFree{}, fmt.Errorf("storage %s not reported by the node", storage)
}

// Eligible: active, content includes `rootdir`, and the agent holds Datastore.AllocateSpace on
// /storage/<id>. The permission is read for the SPECIFIC privilege — the box-wide grant answers every
// path with inherited privileges (proxmox.Client.Permissions).
func (p *Provider) Eligible(ctx context.Context) ([]string, error) {
	live, err := p.API.NodeStorage(ctx)
	if err != nil {
		return nil, fmt.Errorf("node storage: %w", err)
	}
	var out []string
	for _, s := range live {
		if s.Active != 1 || !hasContent(s.Content, "rootdir") {
			continue
		}
		privs, perr := p.API.Permissions(ctx, "/storage/"+s.Storage)
		if perr != nil || privs["Datastore.AllocateSpace"] != 1 {
			continue
		}
		out = append(out, s.Storage)
	}
	return out, nil
}

func hasContent(list, want string) bool {
	for _, c := range strings.Split(list, ",") {
		if strings.TrimSpace(c) == want {
			return true
		}
	}
	return false
}