/*
   Copyright 2017-2019 Jan Dittberner

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this program except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
*/
package main

import (
	"database/sql"
	"fmt"
	"github.com/jmoiron/sqlx"
	"github.com/rubenv/sql-migrate"
	"time"

	migrations "git.cacert.org/cacert-boardvoting/db"
	log "github.com/sirupsen/logrus"
)

type sqlKey int

const (
	sqlLoadDecisions sqlKey = iota
	sqlLoadUnvotedDecisions
	sqlLoadDecisionByTag
	sqlLoadDecisionById
	sqlLoadVoteCountsForDecision
	sqlLoadVotesForDecision
	sqlLoadEnabledVoterByEmail
	sqlCountOlderThanDecision
	sqlCountOlderThanUnvotedDecision
	sqlCreateDecision
	sqlUpdateDecision
	sqlUpdateDecisionStatus
	sqlSelectClosableDecisions
	sqlGetNextPendingDecisionDue
	sqlGetReminderVoters
	sqlFindUnvotedDecisionsForVoter
	sqlGetEnabledVoterById
	sqlCreateVote
	sqlLoadVote
	sqlGetVotersForProxy
)

var sqlStatements = map[sqlKey]string{
	sqlLoadDecisions: `
SELECT decisions.id, decisions.tag, decisions.proponent, voters.name AS proposer, decisions.proposed, decisions.title,
       decisions.content, decisions.votetype, decisions.status, decisions.due, decisions.modified
FROM   decisions
JOIN   voters ON decisions.proponent=voters.id
ORDER BY proposed DESC
LIMIT 10 OFFSET 10 * $1`,
	sqlLoadUnvotedDecisions: `
SELECT decisions.id, decisions.tag, decisions.proponent, voters.name AS proposer, decisions.proposed, decisions.title,
       decisions.content, decisions.votetype, decisions.status, decisions.due, decisions.modified
FROM   decisions
JOIN   voters ON decisions.proponent=voters.id
WHERE  decisions.status = 0 AND decisions.id NOT IN (SELECT votes.decision FROM votes WHERE votes.voter = $1)
ORDER BY proposed DESC
LIMIT 10 OFFSET 10 * $2;`,
	sqlLoadDecisionByTag: `
SELECT decisions.id, decisions.tag, decisions.proponent, voters.name AS proposer, decisions.proposed, decisions.title,
       decisions.content, decisions.votetype, decisions.status, decisions.due, decisions.modified
FROM   decisions
JOIN   voters ON decisions.proponent=voters.id
WHERE  decisions.tag=$1;`,
	sqlLoadDecisionById: `
SELECT decisions.id, decisions.tag, decisions.proponent, decisions.proposed, decisions.title, decisions.content,
       decisions.votetype, decisions.status, decisions.due, decisions.modified
FROM   decisions
WHERE  decisions.id=$1;`,
	sqlLoadVoteCountsForDecision: `
SELECT vote, COUNT(vote) FROM votes WHERE decision=$1 GROUP BY vote`,
	sqlLoadVotesForDecision: `
SELECT votes.decision, votes.voter, voters.name, votes.vote, votes.voted, votes.notes
FROM   votes
JOIN   voters ON votes.voter=voters.id
WHERE  decision=$1`,
	sqlLoadEnabledVoterByEmail: `
SELECT voters.id, voters.name, voters.enabled, voters.reminder
FROM   voters
JOIN   emails ON voters.id=emails.voter
WHERE  emails.address=$1 AND voters.enabled=1`,
	sqlGetEnabledVoterById: `
SELECT id, name, enabled, reminder
FROM   voters
WHERE  enabled=1 AND id=$1`,
	sqlCountOlderThanDecision: `
SELECT COUNT(*) > 0 FROM decisions WHERE proposed < $1`,
	sqlCountOlderThanUnvotedDecision: `
SELECT COUNT(*) > 0 FROM decisions
WHERE  proposed < $1 AND status=0 AND id NOT IN (SELECT decision FROM votes WHERE votes.voter=$2)`,
	sqlCreateDecision: `
INSERT INTO decisions (proposed, proponent, title, content, votetype, status, due, modified,tag)
VALUES (
    :proposed, :proponent, :title, :content, :votetype, 0, :due, :proposed,
    'm' || strftime('%Y%m%d', :proposed) || '.' || (
	 	SELECT COUNT(*)+1 AS num
  		FROM decisions
  		WHERE proposed BETWEEN date(:proposed) AND date(:proposed, '1 day')
    )
)`,
	sqlUpdateDecision: `
UPDATE decisions
SET    proponent=:proponent, title=:title, content=:content, votetype=:votetype, due=:due, modified=:modified
WHERE  id=:id`,
	sqlUpdateDecisionStatus: `
UPDATE decisions SET status=:status, modified=:modified WHERE id=:id`,
	sqlSelectClosableDecisions: `
SELECT decisions.id, decisions.tag, decisions.proponent, decisions.proposed, decisions.title, decisions.content,
       decisions.votetype, decisions.status, decisions.due, decisions.modified
FROM   decisions
WHERE  decisions.status=0 AND :now > due`,
	sqlGetNextPendingDecisionDue: `
SELECT due FROM decisions WHERE status=0 ORDER BY due LIMIT 1`,
	sqlGetVotersForProxy: `
SELECT id, name, reminder
FROM   voters WHERE enabled=1 AND id != $1`,
	sqlGetReminderVoters: `
SELECT id, name, reminder FROM voters WHERE enabled=1 AND reminder!='' AND reminder IS NOT NULL`,
	sqlFindUnvotedDecisionsForVoter: `
SELECT tag, title, votetype, due
FROM   decisions
WHERE  status = 0 AND id NOT IN (SELECT decision FROM votes WHERE voter = $1)
ORDER BY due ASC`,
	sqlCreateVote: `
INSERT OR REPLACE INTO votes (decision, voter, vote, voted, notes)
VALUES (:decision, :voter, :vote, :voted, :notes)`,
	sqlLoadVote: `
SELECT decision, voter, vote, voted, notes
FROM   votes
WHERE  decision=$1 AND voter=$2`,
}

type VoteType uint8
type VoteStatus int8

type Decision struct {
	Id          int64
	Proposed    time.Time
	ProponentId int64 `db:"proponent"`
	Title       string
	Content     string
	Quorum      int
	Majority    int
	Status      VoteStatus
	Due         time.Time
	Modified    time.Time
	Tag         string
	VoteType    VoteType
}

type Voter struct {
	Id       int64
	Name     string
	Enabled  bool
	Reminder string // reminder email address
}

type VoteChoice int

const (
	voteAye     = 1
	voteNaye    = -1
	voteAbstain = 0
)

const (
	voteTypeMotion = 0
	voteTypeVeto   = 1
)

func (v VoteType) String() string {
	switch v {
	case voteTypeMotion:
		return "motion"
	case voteTypeVeto:
		return "veto"
	default:
		return "unknown"
	}
}

func (v VoteType) QuorumAndMajority() (int, int) {
	switch v {
	case voteTypeMotion:
		return 3, 50
	default:
		return 1, 99
	}
}

func (v VoteChoice) String() string {
	switch v {
	case voteAye:
		return "aye"
	case voteNaye:
		return "naye"
	case voteAbstain:
		return "abstain"
	default:
		return "unknown"
	}
}

var VoteValues = map[string]VoteChoice{
	"aye":     voteAye,
	"naye":    voteNaye,
	"abstain": voteAbstain,
}

var VoteChoices = map[int64]VoteChoice{
	1:  voteAye,
	0:  voteAbstain,
	-1: voteNaye,
}

const (
	voteStatusDeclined  = -1
	voteStatusPending   = 0
	voteStatusApproved  = 1
	voteStatusWithdrawn = -2
)

func (v VoteStatus) String() string {
	switch v {
	case voteStatusDeclined:
		return "declined"
	case voteStatusPending:
		return "pending"
	case voteStatusApproved:
		return "approved"
	case voteStatusWithdrawn:
		return "withdrawn"
	default:
		return "unknown"
	}
}

type Vote struct {
	DecisionId int64 `db:"decision"`
	VoterId    int64 `db:"voter"`
	Vote       VoteChoice
	Voted      time.Time
	Notes      string
}

type dbHandler struct {
	db *sqlx.DB
}

var db *dbHandler

func NewDB(database *sql.DB) *dbHandler {
	handler := &dbHandler{db: sqlx.NewDb(database, "sqlite3")}
	_, err := migrate.Exec(database, "sqlite3", migrations.Migrations(), migrate.Up)
	if err != nil {
		log.Panicf("running database migration failed: %v", err)
	}

	failedStatements := make([]string, 0)
	for _, sqlStatement := range sqlStatements {
		var stmt *sqlx.Stmt
		stmt, err := handler.db.Preparex(sqlStatement)
		if err != nil {
			log.Errorf("error parsing statement %s: %s", sqlStatement, err)
			failedStatements = append(failedStatements, sqlStatement)
		}
		_ = stmt.Close()
	}
	if len(failedStatements) > 0 {
		log.Panicf("%d statements failed to prepare", len(failedStatements))
	}

	return handler
}

func (d *dbHandler) Close() error {
	return d.db.Close()
}

func (d *dbHandler) getPreparedNamedStatement(statementKey sqlKey) *sqlx.NamedStmt {
	statement, err := d.db.PrepareNamed(sqlStatements[statementKey])
	if err != nil {
		log.Panicf("Preparing statement failed: %v", err)
	}
	return statement
}

func (d *dbHandler) getPreparedStatement(statementKey sqlKey) *sqlx.Stmt {
	statement, err := d.db.Preparex(sqlStatements[statementKey])
	if err != nil {
		log.Panicf("Preparing statement failed: %v", err)
	}
	return statement
}

func (v *Vote) Save() (err error) {
	insertVoteStmt := db.getPreparedNamedStatement(sqlCreateVote)
	defer func() { _ = insertVoteStmt.Close() }()

	if _, err = insertVoteStmt.Exec(v); err != nil {
		log.Errorf("saving vote failed: %v", err)
		return
	}

	getVoteStmt := db.getPreparedStatement(sqlLoadVote)
	defer func() { _ = getVoteStmt.Close() }()

	if err = getVoteStmt.Get(v, v.DecisionId, v.VoterId); err != nil {
		log.Errorf("getting inserted vote failed: %v", err)
		return
	}

	return
}

type VoteSums struct {
	Ayes     int
	Nayes    int
	Abstains int
}

func (v *VoteSums) VoteCount() int {
	return v.Ayes + v.Nayes + v.Abstains
}

func (v *VoteSums) TotalVotes() int {
	return v.Ayes + v.Nayes
}

func (v *VoteSums) Percent() int {
	totalVotes := v.TotalVotes()
	if totalVotes == 0 {
		return 0
	}
	return v.Ayes * 100 / totalVotes
}

func (v *VoteSums) CalculateResult(quorum int, majority int) (status VoteStatus, reasoning string) {
	if v.VoteCount() < quorum {
		status, reasoning = voteStatusDeclined, fmt.Sprintf("Needed quorum of %d has not been reached.", quorum)
	} else if (v.Ayes / v.TotalVotes()) < (majority / 100) {
		status, reasoning = voteStatusDeclined, fmt.Sprintf("Needed majority of %d%% has not been reached.", majority)
	} else {
		status, reasoning = voteStatusApproved, "Quorum and majority have been reached"
	}
	return
}

type VoteForDisplay struct {
	Vote
	Name string
}

type DecisionForDisplay struct {
	Decision
	Proposer string `db:"proposer"`
	*VoteSums
	Votes []VoteForDisplay
}

func FindDecisionForDisplayByTag(tag string) (decision *DecisionForDisplay, err error) {
	decisionStmt := db.getPreparedStatement(sqlLoadDecisionByTag)
	defer func() { _ = decisionStmt.Close() }()

	decision = &DecisionForDisplay{}
	if err = decisionStmt.Get(decision, tag); err != nil {
		if err == sql.ErrNoRows {
			decision = nil
			err = nil
			return
		} else {
			log.Errorf("getting motion %s failed: %v", tag, err)
			return
		}
	}
	decision.VoteSums, err = decision.Decision.VoteSums()
	return
}

// FindDecisionsForDisplayOnPage loads a set of decisions from the database.
//
// This function uses OFFSET for pagination which is not a good idea for larger data sets.
//
// TODO: migrate to timestamp base pagination
func FindDecisionsForDisplayOnPage(page int64, unvoted bool, voter *Voter) (decisions []*DecisionForDisplay, err error) {
	var decisionsStmt *sqlx.Stmt
	if unvoted && voter != nil {
		decisionsStmt = db.getPreparedStatement(sqlLoadUnvotedDecisions)
	} else {
		decisionsStmt = db.getPreparedStatement(sqlLoadDecisions)
	}
	defer func() { _ = decisionsStmt.Close() }()

	var rows *sqlx.Rows
	if unvoted && voter != nil {
		rows, err = decisionsStmt.Queryx(voter.Id, page-1)
	} else {
		rows, err = decisionsStmt.Queryx(page - 1)
	}
	if err != nil {
		log.Errorf("loading motions for page %d failed: %v", page, err)
		return
	}
	defer func() { _ = rows.Close() }()

	for rows.Next() {
		var d DecisionForDisplay
		if err = rows.StructScan(&d); err != nil {
			log.Errorf("loading motions for page %d failed: %v", page, err)
			return
		}
		d.VoteSums, err = d.Decision.VoteSums()
		if err != nil {
			return
		}
		decisions = append(decisions, &d)
	}
	return
}

func (d *Decision) VoteSums() (sums *VoteSums, err error) {
	votesStmt := db.getPreparedStatement(sqlLoadVoteCountsForDecision)
	defer func() { _ = votesStmt.Close() }()

	voteRows, err := votesStmt.Queryx(d.Id)
	if err != nil {
		log.Errorf("fetching vote sums for motion %s failed: %v", d.Tag, err)
		return
	}
	defer func() { _ = voteRows.Close() }()

	sums = &VoteSums{}
	for voteRows.Next() {
		var vote VoteChoice
		var count int
		if err = voteRows.Scan(&vote, &count); err != nil {
			log.Errorf("fetching vote sums for motion %s failed: %v", d.Tag, err)
			return
		}
		switch vote {
		case voteAye:
			sums.Ayes = count
		case voteNaye:
			sums.Nayes = count
		case voteAbstain:
			sums.Abstains = count
		}
	}
	return
}

func (d *DecisionForDisplay) LoadVotes() (err error) {
	votesStmt := db.getPreparedStatement(sqlLoadVotesForDecision)
	defer func() { _ = votesStmt.Close() }()

	err = votesStmt.Select(&d.Votes, d.Id)
	if err != nil {
		log.Errorf("selecting votes for motion %s failed: %v", d.Tag, err)
		return
	}
	return
}

func (d *Decision) OlderExists(unvoted bool, voter *Voter) (result bool, err error) {
	if unvoted && voter != nil {
		olderStmt := db.getPreparedStatement(sqlCountOlderThanUnvotedDecision)
		defer func() { _ = olderStmt.Close() }()

		if err = olderStmt.Get(&result, d.Proposed, voter.Id); err != nil {
			log.Errorf("finding older motions than %s failed: %v", d.Tag, err)
			return
		}
	} else {
		olderStmt := db.getPreparedStatement(sqlCountOlderThanDecision)
		defer func() { _ = olderStmt.Close() }()

		if err = olderStmt.Get(&result, d.Proposed); err != nil {
			log.Errorf("finding older motions than %s failed: %v", d.Tag, err)
			return
		}
	}

	return
}

func (d *Decision) Create() (err error) {
	insertDecisionStmt := db.getPreparedNamedStatement(sqlCreateDecision)
	defer func() { _ = insertDecisionStmt.Close() }()

	result, err := insertDecisionStmt.Exec(d)
	if err != nil {
		log.Errorf("creating motion failed: %v", err)
		return
	}

	lastInsertId, err := result.LastInsertId()
	if err != nil {
		log.Errorf("getting id of inserted motion failed: %v", err)
		return
	}
	rescheduleChannel <- JobIdCloseDecisions

	getDecisionStmt := db.getPreparedStatement(sqlLoadDecisionById)
	defer func() { _ = getDecisionStmt.Close() }()

	err = getDecisionStmt.Get(d, lastInsertId)
	if err != nil {
		log.Errorf("getting inserted motion failed: %v", err)
		return
	}

	return
}

func (d *Decision) LoadWithId() (err error) {
	getDecisionStmt := db.getPreparedStatement(sqlLoadDecisionById)
	defer func() { _ = getDecisionStmt.Close() }()

	err = getDecisionStmt.Get(d, d.Id)
	if err != nil {
		log.Errorf("loading updated motion failed: %v", err)
		return
	}

	return
}

func (d *Decision) Update() (err error) {
	updateDecisionStmt := db.getPreparedNamedStatement(sqlUpdateDecision)
	defer func() { _ = updateDecisionStmt.Close() }()

	result, err := updateDecisionStmt.Exec(d)
	if err != nil {
		log.Errorf("updating motion failed: %v", err)
		return
	}
	affectedRows, err := result.RowsAffected()
	if err != nil {
		log.Error("Problem determining the affected rows")
		return
	} else if affectedRows != 1 {
		log.Warningf("wrong number of affected rows: %d (1 expected)", affectedRows)
	}
	rescheduleChannel <- JobIdCloseDecisions

	err = d.LoadWithId()
	return
}

func (d *Decision) UpdateStatus() (err error) {
	updateStatusStmt := db.getPreparedNamedStatement(sqlUpdateDecisionStatus)
	defer func() { _ = updateStatusStmt.Close() }()

	result, err := updateStatusStmt.Exec(d)
	if err != nil {
		log.Errorf("setting motion status failed: %v", err)
		return
	}
	affectedRows, err := result.RowsAffected()
	if err != nil {
		log.Errorf("determining the affected rows failed: %v", err)
		return
	} else if affectedRows != 1 {
		log.Warningf("wrong number of affected rows: %d (1 expected)", affectedRows)
	}
	rescheduleChannel <- JobIdCloseDecisions

	err = d.LoadWithId()
	return
}

func (d *Decision) String() string {
	return fmt.Sprintf("%s %s (Id %d)", d.Tag, d.Title, d.Id)
}

func FindVoterByAddress(emailAddress string) (voter *Voter, err error) {
	findVoterStmt := db.getPreparedStatement(sqlLoadEnabledVoterByEmail)
	defer func() { _ = findVoterStmt.Close() }()

	voter = &Voter{}
	if err = findVoterStmt.Get(voter, emailAddress); err != nil {
		if err != sql.ErrNoRows {
			log.Errorf("getting voter for address %s failed: %v", emailAddress, err)
		} else {
			err = nil
			voter = nil
		}
	}
	return
}

func (d *Decision) Close() error {
	quorum, majority := d.VoteType.QuorumAndMajority()

	var voteSums *VoteSums
	var err error

	if voteSums, err = d.VoteSums(); err != nil {
		log.Errorf("getting vote sums failed: %v", err)
		return err
	}
	var reasoning string
	d.Status, reasoning = voteSums.CalculateResult(quorum, majority)

	closeDecisionStmt := db.getPreparedNamedStatement(sqlUpdateDecisionStatus)
	defer func() { _ = closeDecisionStmt.Close() }()

	result, err := closeDecisionStmt.Exec(d)
	if err != nil {
		log.Errorf("closing vote failed: %v", err)
		return err
	}
	if affectedRows, err := result.RowsAffected(); err != nil {
		log.Errorf("getting affected rows failed: %v", err)
		return err
	} else if affectedRows != 1 {
		log.Warningf("wrong number of affected rows: %d (1 expected)", affectedRows)
	}

	NotifyMailChannel <- NewNotificationClosedDecision(d, voteSums, reasoning)

	log.Infof("decision %s closed with result %s: reasoning %s", d.Tag, d.Status, reasoning)

	return nil
}

func CloseDecisions() (err error) {
	getClosableDecisionsStmt := db.getPreparedNamedStatement(sqlSelectClosableDecisions)
	defer func() { _ = getClosableDecisionsStmt.Close() }()

	decisions := make([]*Decision, 0)
	rows, err := getClosableDecisionsStmt.Queryx(struct{ Now time.Time }{time.Now().UTC()})
	if err != nil {
		log.Errorf("fetching closable decisions failed: %v", err)
		return
	}
	defer func() { _ = rows.Close() }()
	for rows.Next() {
		decision := &Decision{}
		if err = rows.StructScan(decision); err != nil {
			log.Errorf("scanning row failed: %v", err)
			return
		}
		decisions = append(decisions, decision)
	}
	defer func() { _ = rows.Close() }()

	for _, decision := range decisions {
		log.Infof("found closable decision %s", decision.Tag)
		if err = decision.Close(); err != nil {
			log.Errorf("closing decision %s failed: %s", decision.Tag, err)
			return
		}
	}

	return
}

func GetNextPendingDecisionDue() (due *time.Time, err error) {
	getNextPendingDecisionDueStmt := db.getPreparedStatement(sqlGetNextPendingDecisionDue)
	defer func() { _ = getNextPendingDecisionDueStmt.Close() }()

	row := getNextPendingDecisionDueStmt.QueryRow()

	due = &time.Time{}
	if err = row.Scan(due); err != nil {
		if err == sql.ErrNoRows {
			log.Debug("No pending decisions")
			return nil, nil
		}
		log.Errorf("parsing result failed: %v", err)
		return nil, err
	}

	return
}

func GetReminderVoters() (voters *[]Voter, err error) {
	getReminderVotersStmt := db.getPreparedStatement(sqlGetReminderVoters)
	defer func() { _ = getReminderVotersStmt.Close() }()

	voterSlice := make([]Voter, 0)

	if err = getReminderVotersStmt.Select(&voterSlice); err != nil {
		log.Errorf("getting voters failed: %v", err)
		return
	}
	voters = &voterSlice

	return
}

func FindUnvotedDecisionsForVoter(voter *Voter) (decisions *[]Decision, err error) {
	findUnvotedDecisionsForVoterStmt := db.getPreparedStatement(sqlFindUnvotedDecisionsForVoter)
	defer func() { _ = findUnvotedDecisionsForVoterStmt.Close() }()

	decisionsSlice := make([]Decision, 0)

	if err = findUnvotedDecisionsForVoterStmt.Select(&decisionsSlice, voter.Id); err != nil {
		log.Errorf("getting unvoted decisions failed: %v", err)
		return
	}
	decisions = &decisionsSlice

	return
}

func GetVoterById(id int64) (voter *Voter, err error) {
	getVoterByIdStmt := db.getPreparedStatement(sqlGetEnabledVoterById)
	defer func() { _ = getVoterByIdStmt.Close() }()

	voter = &Voter{}
	if err = getVoterByIdStmt.Get(voter, id); err != nil {
		log.Errorf("getting voter failed: %v", err)
		return
	}

	return
}

func GetVotersForProxy(proxy *Voter) (voters *[]Voter, err error) {
	getVotersForProxyStmt := db.getPreparedStatement(sqlGetVotersForProxy)
	defer func() { _ = getVotersForProxyStmt.Close() }()

	votersSlice := make([]Voter, 0)

	if err = getVotersForProxyStmt.Select(&votersSlice, proxy.Id); err != nil {
		log.Errorf("Error getting voters for proxy failed: %v", err)
		return
	}
	voters = &votersSlice

	return
}