// Copyright 2016 Keybase, Inc. All rights reserved. Use of
// this source code is governed by the included BSD license.

package engine

import (
	"bufio"
	"encoding/csv"
	"encoding/gob"
	"fmt"
	"io"
	"os"
	"strconv"
	"strings"
	"time"

	"github.com/keybase/client/go/libkb"
	keybase1 "github.com/keybase/client/go/protocol/keybase1"
)

type ScanProofsCacheData struct {
	// Map from sigid to whether the proof is ok.
	Proofs map[string]bool
}

type ScanProofsCache struct {
	data  ScanProofsCacheData
	dirty bool
}

func NewScanProofsCache() *ScanProofsCache {
	return &ScanProofsCache{
		data: ScanProofsCacheData{
			Proofs: make(map[string]bool),
		},
		dirty: false,
	}
}

func LoadScanProofsCache(filepath string) (*ScanProofsCache, error) {
	f, err := os.Open(filepath)
	if err != nil {
		return nil, err
	}
	dec := gob.NewDecoder(f)
	var c ScanProofsCache
	err = dec.Decode(&c.data)
	if err != nil {
		return nil, err
	}
	return &c, nil
}

func (c *ScanProofsCache) Get(sigID string) bool {
	return c.data.Proofs[sigID]
}

func (c *ScanProofsCache) Set(sigID string) {
	if !c.data.Proofs[sigID] {
		c.dirty = true
	}
	c.data.Proofs[sigID] = true
}

func (c *ScanProofsCache) Save(filepath string) error {
	if !c.dirty {
		// Don't save if nothing has changed
		return nil
	}
	temppath, f, err := libkb.OpenTempFile(filepath, "", 0644)
	if err != nil {
		return err
	}
	enc := gob.NewEncoder(f)
	err = enc.Encode(c.data)
	if err != nil {
		f.Close()
		return err
	}
	f.Close()
	err = os.Rename(temppath, filepath)
	if err != nil {
		return err
	}
	c.dirty = false
	return nil
}

type ScanProofsTickers map[keybase1.ProofType]*time.Ticker

type ScanProofsEngine struct {
	libkb.Contextified
	infile     string
	indices    string
	sigid      string
	ratelimit  int
	cachefile  string
	ignorefile string
}

var _ Engine2 = (*ScanProofsEngine)(nil)

func NewScanProofsEngine(infile string, indices string, sigid string, ratelimit int, cachefile string, ignorefile string, g *libkb.GlobalContext) *ScanProofsEngine {
	return &ScanProofsEngine{
		infile:       infile,
		indices:      indices,
		sigid:        sigid,
		ratelimit:    ratelimit,
		cachefile:    cachefile,
		ignorefile:   ignorefile,
		Contextified: libkb.NewContextified(g),
	}
}

func (e *ScanProofsEngine) Name() string {
	return "ScanProofs"
}

func (e *ScanProofsEngine) Prereqs() Prereqs {
	return Prereqs{}
}

func (e *ScanProofsEngine) RequiredUIs() []libkb.UIKind {
	return []libkb.UIKind{
		libkb.LogUIKind,
	}
}

func (e *ScanProofsEngine) SubConsumers() []libkb.UIConsumer {
	return []libkb.UIConsumer{}
}

func (e *ScanProofsEngine) Run(m libkb.MetaContext) (err error) {
	defer m.Trace("ScanProofsEngine#Run", func() error { return err })()

	var cache *ScanProofsCache
	saveevery := 10
	var ignored []string

	if len(e.cachefile) > 0 {
		lcache, err := LoadScanProofsCache(e.cachefile)
		if err == nil {
			m.Info("Using cache: %v (%v entries)", e.cachefile, len(lcache.data.Proofs))
			cache = lcache
		} else {
			m.Warning("Could not load cache: %v", err)
			cache = NewScanProofsCache()
		}
	}

	if len(e.ignorefile) > 0 {
		ignored, err = LoadScanProofsIgnore(e.ignorefile)
		if err != nil {
			return fmt.Errorf("Could not open ignore file: %v", err)
		}
		m.Info("Using ignore file: %v (%v entries)", e.ignorefile, len(ignored))
	}

	if len(e.sigid) > 0 && len(e.indices) > 0 {
		return fmt.Errorf("Only one of sigid and indices allowed")
	}

	// One ticker for each proof type.
	var tickers = make(map[keybase1.ProofType]*time.Ticker)
	m.Info("Running with ratelimit: %v ms", e.ratelimit)
	if e.ratelimit < 0 {
		return fmt.Errorf("Ratelimit value can not be negative: %v", e.ratelimit)
	}
	if e.ratelimit > 0 {
		for _, ptype := range keybase1.ProofTypeMap {
			switch ptype {
			case keybase1.ProofType_GENERIC_WEB_SITE, keybase1.ProofType_DNS:
				// Web sites and DNS do not need a rate limit.
			default:
				tickers[ptype] = time.NewTicker(time.Millisecond * time.Duration(e.ratelimit))
			}
		}
	}
	defer func(tickers *map[keybase1.ProofType]*time.Ticker) {
		for _, ticker := range *tickers {
			if ticker != nil {
				ticker.Stop()
			}
		}
	}(&tickers)

	f, err := os.Open(e.infile)
	if err != nil {
		return err
	}
	r := csv.NewReader(f)

	var records []map[string]string

	header, err := r.Read()
	if err != nil {
		return fmt.Errorf("Could not read header: %v", err)
	}

	m.Debug("Reading csv... ")
	for {
		rec, err := r.Read()
		if err == io.EOF {
			break
		}
		if err != nil {
			return err
		}
		record := make(map[string]string)
		for i, val := range rec {
			record[header[i]] = val
		}
		records = append(records, record)
	}
	m.Debug("done")

	startindex := 0
	endindex := len(records)
	if len(e.indices) > 0 {
		startindex, endindex, err = e.ParseIndices(e.indices)
		if err != nil {
			return err
		}
	}
	if startindex < 0 {
		return fmt.Errorf("Invalid start index: %v", startindex)
	}
	if endindex > len(records) {
		return fmt.Errorf("Invalid end index: %v (%v records)", endindex, len(records))
	}

	nrun := 0
	nok := 0

	for i := startindex; i < endindex; i++ {
		rec := records[i]

		if len(e.sigid) > 0 && e.sigid != rec["sig_id"] {
			continue
		}

		m.Info("i:%v user:%v type:%v sigid:%v", i, rec["username"], rec["proof_type"], rec["sig_id"])

		err := e.ProcessOne(m, i, rec, cache, ignored, tickers)
		nrun++
		if err == nil {
			m.Info("Ok\n")
			nok++
			if cache != nil {
				cache.Set(rec["sig_id"])
				if i%saveevery == 0 {
					saveerr := cache.Save(e.cachefile)
					if saveerr != nil {
						m.Warning("Could not save cache: %v", saveerr)
					}
				}
			}
		} else {
			m.Error("%v FAILED: %v\n", i, err)
		}
	}

	m.Info("---")
	m.Info("proofs checked  : %v", nrun)
	m.Info("oks             : %v", nok)
	m.Info("fails           : %v", nrun-nok)

	if cache != nil {
		saveerr := cache.Save(e.cachefile)
		if saveerr != nil {
			m.Warning("Could not save cache: %v", saveerr)
		}
	}

	return nil
}

func (e *ScanProofsEngine) ProcessOne(m libkb.MetaContext, i int, rec map[string]string, cache *ScanProofsCache, ignored []string, tickers ScanProofsTickers) error {
	serverstate, err := strconv.Atoi(rec["state"])
	if err != nil {
		return fmt.Errorf("Could not read server state: %v", err)
	}

	shouldsucceed := true
	skip := false
	var skipreason string
	badstate := false

	switch keybase1.ProofState(serverstate) {
	case keybase1.ProofState_NONE:
		badstate = true
	case keybase1.ProofState_OK:
	case keybase1.ProofState_TEMP_FAILURE:
		shouldsucceed = false
	case keybase1.ProofState_PERM_FAILURE:
		shouldsucceed = false
	case keybase1.ProofState_LOOKING:
		skip = true
		skipreason = "server LOOKING"
	case keybase1.ProofState_SUPERSEDED:
		skip = true
		skipreason = "server SUPERSEDED"
	case keybase1.ProofState_POSTED:
		badstate = true
	case keybase1.ProofState_REVOKED:
		skip = true
		skipreason = "server REVOKED"
	case keybase1.ProofState_DELETED:
		skip = true
		skipreason = "server DELETED"
	default:
		badstate = true
	}

	if cache != nil && cache.Get(rec["sig_id"]) {
		skip = true
		skipreason = "cached success"
	}

	for _, x := range ignored {
		if x == rec["sig_id"] {
			skip = true
			skipreason = "in ignored list"
		}
	}

	if badstate {
		return fmt.Errorf("Unsupported serverstate: %v", serverstate)
	}

	if skip {
		m.Info("skipping: %v", skipreason)
		return nil
	}

	deluserstr := "Error loading user: Deleted"
	perr1, foundhint1, err := e.CheckOne(m, rec, tickers)
	if err != nil {
		if err.Error() == deluserstr {
			m.Info("deleted user")
			return nil
		}
		return err
	}
	// Skip the rate limit on the second check.
	perr2, foundhint2, err := e.CheckOne(m, rec, nil)
	if err != nil {
		return err
	}

	if foundhint1 != foundhint2 {
		return fmt.Errorf("Local verifiers disagree: foundhint1:%v foundhint:%v (likely timing)",
			foundhint1, foundhint2)
	}

	if (perr1 == nil) != (perr2 == nil) {
		return fmt.Errorf("Local verifiers disagree:\n  %v\n  %v", perr1, perr2)
	}

	succeeded := foundhint1 && (perr1 == nil)

	if succeeded != shouldsucceed {
		return fmt.Errorf("Local verifiers disagree with server: server:%v client:%v", serverstate, perr1)
	}

	return nil
}

// CheckOne checks one proof using two checkers (default, pvl).
// NOTE: This doesn't make sense anymore because pvl is the default.
// Returns nil or an error, whether a hint was found, and any more serious error
func (e *ScanProofsEngine) CheckOne(m libkb.MetaContext, rec map[string]string, tickers ScanProofsTickers) (libkb.ProofError, bool, error) {
	uid := keybase1.UID(rec["uid"])
	sigid := keybase1.SigID(rec["sig_id"])

	foundhint := false
	hint, err := e.GetSigHint(m, uid, sigid)
	if err != nil {
		return nil, foundhint, err
	}
	if hint == nil {
		return nil, foundhint, nil
	}
	foundhint = true

	link, err := e.GetRemoteProofChainLink(m, uid, sigid)
	if err != nil {
		return nil, foundhint, err
	}

	pc, err := libkb.MakeProofChecker(m, m.G().GetProofServices(), link)
	if err != nil {
		return nil, foundhint, err
	}

	// Beyond this point, external requests will occur, and rate limiting is used
	ptype := link.GetProofType()
	if tickers[ptype] != nil {
		m.Info("Waiting for ticker: %v (%v)", keybase1.ProofTypeRevMap[ptype], ptype)
		<-tickers[ptype].C
	}

	pvlSource := m.G().GetPvlSource()
	if pvlSource == nil {
		return nil, foundhint, fmt.Errorf("no pvl source for proof verification")
	}
	pvlU, err := pvlSource.GetLatestEntry(m)
	if err != nil {
		return nil, foundhint, fmt.Errorf("error getting pvl: %s", err)
	}

	if _, perr := pc.CheckStatus(m, *hint, libkb.ProofCheckerModeActive, pvlU); perr != nil {
		return perr, foundhint, nil
	}

	return nil, foundhint, nil
}

// GetSigHint gets the SigHint. This can return (nil, nil) if nothing goes wrong but there is no hint.
func (e *ScanProofsEngine) GetSigHint(m libkb.MetaContext, uid keybase1.UID, sigid keybase1.SigID) (*libkb.SigHint, error) {
	sighints, err := libkb.LoadAndRefreshSigHints(m, uid)
	if err != nil {
		return nil, err
	}

	sighint := sighints.Lookup(sigid)
	if sighint == nil {
		return nil, nil
	}
	return sighint, nil
}

func (e *ScanProofsEngine) GetRemoteProofChainLink(m libkb.MetaContext, uid keybase1.UID, sigid keybase1.SigID) (libkb.RemoteProofChainLink, error) {
	user, err := libkb.LoadUser(libkb.NewLoadUserArgWithMetaContext(m).WithUID(uid))
	if err != nil {
		return nil, fmt.Errorf("Error loading user: %v", err)
	}

	link := user.LinkFromSigID(sigid)
	if link == nil {
		return nil, fmt.Errorf("Could not find link from sigid")
	}

	tlink, w := libkb.NewTypedChainLink(link)
	if w != nil {
		return nil, fmt.Errorf("Could not get typed chain link: %v", w.Warning())
	}

	switch vlink := tlink.(type) {
	case libkb.RemoteProofChainLink:
		return vlink, nil
	default:
		return nil, fmt.Errorf("Link is not a RemoteProofChainLink: %v", tlink)
	}
}

func (e *ScanProofsEngine) ParseIndices(indices string) (start int, end int, reterr error) {
	wrap := func(format string, arg ...interface{}) error {
		f2 := fmt.Sprintf("Invalid indices: %s", format)
		return fmt.Errorf(f2, arg...)
	}
	ss := strings.Split(strings.TrimSpace(indices), ":")
	if len(ss) != 2 {
		return start, end, wrap("must be like start:end")
	}
	var err error
	start, err = strconv.Atoi(ss[0])
	if err != nil {
		return start, end, wrap("could not convert start: %v", err)
	}
	end, err = strconv.Atoi(ss[1])
	if err != nil {
		return start, end, wrap("could not convert end: %v", err)
	}
	if end <= start {
		return start, end, wrap("%v <= %v", end, start)
	}
	reterr = nil
	return
}

// LoadScanProofsIgnore loads an ignore file and returns the list of proofids to ignore.
func LoadScanProofsIgnore(filepath string) ([]string, error) {
	f, err := os.Open(filepath)
	if err != nil {
		return nil, err
	}
	defer f.Close()
	scanner := bufio.NewScanner(f)
	scanner.Split(bufio.ScanLines)
	var ignored []string
	for scanner.Scan() {
		x := strings.TrimSpace(scanner.Text())
		if strings.HasPrefix(x, "//") {
			continue
		}
		ignored = append(ignored, x)
	}
	return ignored, nil
}
