package main

import (
	"database/sql"
	"fmt"
	dbmig "git.cacert.org/cacert-boardvoting/db"
	"github.com/jmoiron/sqlx"
	"github.com/rubenv/sql-migrate"
	"time"
)

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")}
	failedStatements := make([]string, 0)
	for _, sqlStatement := range sqlStatements {
		var stmt *sqlx.Stmt
		stmt, err := handler.db.Preparex(sqlStatement)
		if err != nil {
			log.Critical("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))
	}

	_, err := migrate.Exec(database, "sqlite3", dbmig.Migrations(), migrate.Up)
	if err != nil {
		log.Panicf("running database migration failed: %v", err)
	}
	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 insertVoteStmt.Close()

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

	getVoteStmt := db.getPreparedStatement(sqlLoadVote)
	defer 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 decisionStmt.Close()

	decision = &DecisionForDisplay{}
	if err = decisionStmt.Get(decision, tag); err != nil {
		if err == sql.ErrNoRows {
			decision = nil
			err = nil
		} 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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)
	}
	rows.Close()

	for _, decision := range decisions {
		log.Debugf("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 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 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 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 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 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
}