package stores

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

	"golang.org/x/xerrors"

	"github.com/filecoin-project/specs-actors/actors/abi"
	"github.com/filecoin-project/specs-actors/actors/abi/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

	LastHeartbeat time.Time
	HeartbeatErr  error
}

type HealthReport struct {
	Stat FsStat
	Err  error
}

type SectorIndex interface { // part of storage-miner api
	StorageAttach(context.Context, StorageInfo, 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) error
	StorageDropSector(ctx context.Context, storageId ID, s abi.SectorID, ft SectorFileType) error
	StorageFindSector(ctx context.Context, sector abi.SectorID, ft SectorFileType, allowFetch bool) ([]StorageInfo, error)

	StorageBestAlloc(ctx context.Context, allocate SectorFileType, spt abi.RegisteredProof, sealing bool) ([]StorageInfo, error)
}

type Decl struct {
	abi.SectorID
	SectorFileType
}

type storageEntry struct {
	info *StorageInfo
	fsi  FsStat

	lastHeartbeat time.Time
	heartbeatErr  error
}

type Index struct {
	lk sync.RWMutex

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

func NewIndex() *Index {
	return &Index{
		sectors: map[Decl][]ID{},
		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][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 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) error {
	i.lk.Lock()
	defer i.lk.Unlock()

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

		d := Decl{s, fileType}

		for _, sid := range i.sectors[d] {
			if sid == storageId {
				log.Warnf("sector %v redeclared in %s", s, storageId)
				return nil
			}
		}

		i.sectors[d] = append(i.sectors[d], storageId)
	}

	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([]ID, 0, len(i.sectors[d])-1)
		for _, sid := range i.sectors[d] {
			if sid == 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, allowFetch bool) ([]StorageInfo, error) {
	i.lk.RLock()
	defer i.lk.RUnlock()

	storageIDs := map[ID]uint64{}

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

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

	out := make([]StorageInfo, 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, StorageInfo{
			ID:       id,
			URLs:     urls,
			Weight:   st.info.Weight * n, // storage with more sector types is better
			CanSeal:  st.info.CanSeal,
			CanStore: st.info.CanStore,
		})
	}

	if allowFetch {
		for id, st := range i.stores {
			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, StorageInfo{
				ID:       id,
				URLs:     urls,
				Weight:   st.info.Weight * 0, // TODO: something better than just '0'
				CanSeal:  st.info.CanSeal,
				CanStore: st.info.CanStore,
			})
		}
	}

	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, spt abi.RegisteredProof, sealing bool) ([]StorageInfo, error) {
	i.lk.RLock()
	defer i.lk.RUnlock()

	var candidates []storageEntry

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

	for _, p := range i.stores {
		if sealing && !p.info.CanSeal {
			continue
		}
		if !sealing && !p.info.CanStore {
			continue
		}

		if spaceReq > 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(int64(candidates[i].fsi.Available)), big.NewInt(int64(candidates[i].info.Weight)))
		jw := big.Mul(big.NewInt(int64(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()

	return i.sectors[Decl{
		SectorID:       id,
		SectorFileType: typ,
	}], nil
}

var _ SectorIndex = &Index{}