package stores

import (
	"context"
	"net/url"
	gopath "path"
	"sort"
	"sync"
	"time"

	"golang.org/x/xerrors"

	"github.com/filecoin-project/lotus/extern/sector-storage/fsutil"

	"github.com/filecoin-project/go-state-types/abi"
	"github.com/filecoin-project/go-state-types/big"
)

var HeartbeatInterval = 10 * time.Second
var SkippedHeartbeatThresh = HeartbeatInterval * 5

// ID identifies sector storage by UUID. One sector storage should map to one
//  filesystem, local or networked / shared by multiple machines
type ID string

type StorageInfo struct {
	ID     ID
	URLs   []string // TODO: Support non-http transports
	Weight uint64

	CanSeal  bool
	CanStore bool
}

type HealthReport struct {
	Stat fsutil.FsStat
	Err  error
}

type SectorStorageInfo struct {
	ID     ID
	URLs   []string // TODO: Support non-http transports
	Weight uint64

	CanSeal  bool
	CanStore bool

	Primary bool
}

type SectorIndex interface { // part of storage-miner api
	StorageAttach(context.Context, StorageInfo, fsutil.FsStat) error
	StorageInfo(context.Context, ID) (StorageInfo, error)
	StorageReportHealth(context.Context, ID, HealthReport) error

	StorageDeclareSector(ctx context.Context, storageID ID, s abi.SectorID, ft SectorFileType, primary bool) error
	StorageDropSector(ctx context.Context, storageID ID, s abi.SectorID, ft SectorFileType) error
	StorageFindSector(ctx context.Context, sector abi.SectorID, ft SectorFileType, ssize abi.SectorSize, allowFetch bool) ([]SectorStorageInfo, error)

	StorageBestAlloc(ctx context.Context, allocate SectorFileType, ssize abi.SectorSize, pathType PathType) ([]StorageInfo, error)

	// atomically acquire locks on all sector file types. close ctx to unlock
	StorageLock(ctx context.Context, sector abi.SectorID, read SectorFileType, write SectorFileType) error
	StorageTryLock(ctx context.Context, sector abi.SectorID, read SectorFileType, write SectorFileType) (bool, error)
}

type Decl struct {
	abi.SectorID
	SectorFileType
}

type declMeta struct {
	storage ID
	primary bool
}

type storageEntry struct {
	info *StorageInfo
	fsi  fsutil.FsStat

	lastHeartbeat time.Time
	heartbeatErr  error
}

type Index struct {
	*indexLocks
	lk sync.RWMutex

	sectors map[Decl][]*declMeta
	stores  map[ID]*storageEntry
}

func NewIndex() *Index {
	return &Index{
		indexLocks: &indexLocks{
			locks: map[abi.SectorID]*sectorLock{},
		},
		sectors: map[Decl][]*declMeta{},
		stores:  map[ID]*storageEntry{},
	}
}

func (i *Index) StorageList(ctx context.Context) (map[ID][]Decl, error) {
	i.lk.RLock()
	defer i.lk.RUnlock()

	byID := map[ID]map[abi.SectorID]SectorFileType{}

	for id := range i.stores {
		byID[id] = map[abi.SectorID]SectorFileType{}
	}
	for decl, ids := range i.sectors {
		for _, id := range ids {
			byID[id.storage][decl.SectorID] |= decl.SectorFileType
		}
	}

	out := map[ID][]Decl{}
	for id, m := range byID {
		out[id] = []Decl{}
		for sectorID, fileType := range m {
			out[id] = append(out[id], Decl{
				SectorID:       sectorID,
				SectorFileType: fileType,
			})
		}
	}

	return out, nil
}

func (i *Index) StorageAttach(ctx context.Context, si StorageInfo, st fsutil.FsStat) error {
	i.lk.Lock()
	defer i.lk.Unlock()

	log.Infof("New sector storage: %s", si.ID)

	if _, ok := i.stores[si.ID]; ok {
		for _, u := range si.URLs {
			if _, err := url.Parse(u); err != nil {
				return xerrors.Errorf("failed to parse url %s: %w", si.URLs, err)
			}
		}

	uloop:
		for _, u := range si.URLs {
			for _, l := range i.stores[si.ID].info.URLs {
				if u == l {
					continue uloop
				}
			}

			i.stores[si.ID].info.URLs = append(i.stores[si.ID].info.URLs, u)
		}

		return nil
	}
	i.stores[si.ID] = &storageEntry{
		info: &si,
		fsi:  st,

		lastHeartbeat: time.Now(),
	}
	return nil
}

func (i *Index) StorageReportHealth(ctx context.Context, id ID, report HealthReport) error {
	i.lk.Lock()
	defer i.lk.Unlock()

	ent, ok := i.stores[id]
	if !ok {
		return xerrors.Errorf("health report for unknown storage: %s", id)
	}

	ent.fsi = report.Stat
	ent.heartbeatErr = report.Err
	ent.lastHeartbeat = time.Now()

	return nil
}

func (i *Index) StorageDeclareSector(ctx context.Context, storageID ID, s abi.SectorID, ft SectorFileType, primary bool) error {
	i.lk.Lock()
	defer i.lk.Unlock()

loop:
	for _, fileType := range PathTypes {
		if fileType&ft == 0 {
			continue
		}

		d := Decl{s, fileType}

		for _, sid := range i.sectors[d] {
			if sid.storage == storageID {
				if !sid.primary && primary {
					sid.primary = true
				} else {
					log.Warnf("sector %v redeclared in %s", s, storageID)
				}
				continue loop
			}
		}

		i.sectors[d] = append(i.sectors[d], &declMeta{
			storage: storageID,
			primary: primary,
		})
	}

	return nil
}

func (i *Index) StorageDropSector(ctx context.Context, storageID ID, s abi.SectorID, ft SectorFileType) error {
	i.lk.Lock()
	defer i.lk.Unlock()

	for _, fileType := range PathTypes {
		if fileType&ft == 0 {
			continue
		}

		d := Decl{s, fileType}

		if len(i.sectors[d]) == 0 {
			return nil
		}

		rewritten := make([]*declMeta, 0, len(i.sectors[d])-1)
		for _, sid := range i.sectors[d] {
			if sid.storage == storageID {
				continue
			}

			rewritten = append(rewritten, sid)
		}
		if len(rewritten) == 0 {
			delete(i.sectors, d)
			return nil
		}

		i.sectors[d] = rewritten
	}

	return nil
}

func (i *Index) StorageFindSector(ctx context.Context, s abi.SectorID, ft SectorFileType, ssize abi.SectorSize, allowFetch bool) ([]SectorStorageInfo, error) {
	i.lk.RLock()
	defer i.lk.RUnlock()

	storageIDs := map[ID]uint64{}
	isprimary := map[ID]bool{}

	for _, pathType := range PathTypes {
		if ft&pathType == 0 {
			continue
		}

		for _, id := range i.sectors[Decl{s, pathType}] {
			storageIDs[id.storage]++
			isprimary[id.storage] = isprimary[id.storage] || id.primary
		}
	}

	out := make([]SectorStorageInfo, 0, len(storageIDs))

	for id, n := range storageIDs {
		st, ok := i.stores[id]
		if !ok {
			log.Warnf("storage %s is not present in sector index (referenced by sector %v)", id, s)
			continue
		}

		urls := make([]string, len(st.info.URLs))
		for k, u := range st.info.URLs {
			rl, err := url.Parse(u)
			if err != nil {
				return nil, xerrors.Errorf("failed to parse url: %w", err)
			}

			rl.Path = gopath.Join(rl.Path, ft.String(), SectorName(s))
			urls[k] = rl.String()
		}

		out = append(out, SectorStorageInfo{
			ID:     id,
			URLs:   urls,
			Weight: st.info.Weight * n, // storage with more sector types is better

			CanSeal:  st.info.CanSeal,
			CanStore: st.info.CanStore,

			Primary: isprimary[id],
		})
	}

	if allowFetch {
		spaceReq, err := ft.SealSpaceUse(ssize)
		if err != nil {
			return nil, xerrors.Errorf("estimating required space: %w", err)
		}

		for id, st := range i.stores {
			if !st.info.CanSeal {
				continue
			}

			if spaceReq > uint64(st.fsi.Available) {
				log.Debugf("not selecting on %s, out of space (available: %d, need: %d)", st.info.ID, st.fsi.Available, spaceReq)
				continue
			}

			if time.Since(st.lastHeartbeat) > SkippedHeartbeatThresh {
				log.Debugf("not selecting on %s, didn't receive heartbeats for %s", st.info.ID, time.Since(st.lastHeartbeat))
				continue
			}

			if st.heartbeatErr != nil {
				log.Debugf("not selecting on %s, heartbeat error: %s", st.info.ID, st.heartbeatErr)
				continue
			}

			if _, ok := storageIDs[id]; ok {
				continue
			}

			urls := make([]string, len(st.info.URLs))
			for k, u := range st.info.URLs {
				rl, err := url.Parse(u)
				if err != nil {
					return nil, xerrors.Errorf("failed to parse url: %w", err)
				}

				rl.Path = gopath.Join(rl.Path, ft.String(), SectorName(s))
				urls[k] = rl.String()
			}

			out = append(out, SectorStorageInfo{
				ID:     id,
				URLs:   urls,
				Weight: st.info.Weight * 0, // TODO: something better than just '0'

				CanSeal:  st.info.CanSeal,
				CanStore: st.info.CanStore,

				Primary: false,
			})
		}
	}

	return out, nil
}

func (i *Index) StorageInfo(ctx context.Context, id ID) (StorageInfo, error) {
	i.lk.RLock()
	defer i.lk.RUnlock()

	si, found := i.stores[id]
	if !found {
		return StorageInfo{}, xerrors.Errorf("sector store not found")
	}

	return *si.info, nil
}

func (i *Index) StorageBestAlloc(ctx context.Context, allocate SectorFileType, ssize abi.SectorSize, pathType PathType) ([]StorageInfo, error) {
	i.lk.RLock()
	defer i.lk.RUnlock()

	var candidates []storageEntry

	spaceReq, err := allocate.SealSpaceUse(ssize)
	if err != nil {
		return nil, xerrors.Errorf("estimating required space: %w", err)
	}

	for _, p := range i.stores {
		if (pathType == PathSealing) && !p.info.CanSeal {
			continue
		}
		if (pathType == PathStorage) && !p.info.CanStore {
			continue
		}

		if spaceReq > uint64(p.fsi.Available) {
			log.Debugf("not allocating on %s, out of space (available: %d, need: %d)", p.info.ID, p.fsi.Available, spaceReq)
			continue
		}

		if time.Since(p.lastHeartbeat) > SkippedHeartbeatThresh {
			log.Debugf("not allocating on %s, didn't receive heartbeats for %s", p.info.ID, time.Since(p.lastHeartbeat))
			continue
		}

		if p.heartbeatErr != nil {
			log.Debugf("not allocating on %s, heartbeat error: %s", p.info.ID, p.heartbeatErr)
			continue
		}

		candidates = append(candidates, *p)
	}

	if len(candidates) == 0 {
		return nil, xerrors.New("no good path found")
	}

	sort.Slice(candidates, func(i, j int) bool {
		iw := big.Mul(big.NewInt(candidates[i].fsi.Available), big.NewInt(int64(candidates[i].info.Weight)))
		jw := big.Mul(big.NewInt(candidates[j].fsi.Available), big.NewInt(int64(candidates[j].info.Weight)))

		return iw.GreaterThan(jw)
	})

	out := make([]StorageInfo, len(candidates))
	for i, candidate := range candidates {
		out[i] = *candidate.info
	}

	return out, nil
}

func (i *Index) FindSector(id abi.SectorID, typ SectorFileType) ([]ID, error) {
	i.lk.RLock()
	defer i.lk.RUnlock()

	f, ok := i.sectors[Decl{
		SectorID:       id,
		SectorFileType: typ,
	}]
	if !ok {
		return nil, nil
	}
	out := make([]ID, 0, len(f))
	for _, meta := range f {
		out = append(out, meta.storage)
	}

	return out, nil
}

var _ SectorIndex = &Index{}