package main

import (
	"database/sql"
	"github.com/jmoiron/sqlx"
	"time"
)

const (
	sqlGetDecisions = `
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`
	sqlGetDecision = `
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;`
	sqlGetVoter = `
SELECT voters.id, voters.name
FROM voters
JOIN emails ON voters.id=emails.voter
WHERE emails.address=$1 AND voters.enabled=1`
	sqlVoteCount = `
SELECT vote, COUNT(vote)
FROM votes
WHERE decision=$1 GROUP BY vote`
	sqlCountOlderThanDecision = `
SELECT COUNT(*) > 0 FROM decisions WHERE proposed < $1`
	sqlGetVotesForDecision = `
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`
	sqlListUnvotedDecisions = `
SELECT decisions.id, decisions.tag, decisions.proponent,
	   voters.name AS proposer, decisions.proposed, decisions.title,
	   decisions.content AS 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 decision FROM votes WHERE votes.voter=$2)
ORDER BY proposed DESC
LIMIT 10 OFFSET 10 * $1`
)

var db *sqlx.DB

type VoteType int
type VoteStatus int

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

type Email struct {
	VoterId int `db:"voter"`
	Address string
}

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

type VoteChoice int

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

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"
	}
}

func (v VoteStatus) String() string {
	switch v {
	case -1:
		return "declined"
	case 0:
		return "pending"
	case 1:
		return "approved"
	case -2:
		return "withdrawn"
	default:
		return "unknown"
	}
}

type VoteSums struct {
	Ayes     int
	Nayes    int
	Abstains int
}

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

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, err := db.Preparex(sqlGetDecision)
	if err != nil {
		logger.Println("Error preparing statement:", err)
		return
	}
	defer decisionStmt.Close()

	decision = &DecisionForDisplay{}
	if err = decisionStmt.Get(decision, tag); err != nil {
		if err == sql.ErrNoRows {
			decision = nil
			err = nil
		} else {
			logger.Printf("Error getting motion %s: %v\n", tag, err)
		}
	}
	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) (decisions []*DecisionForDisplay, err error) {
	decisionsStmt, err := db.Preparex(sqlGetDecisions)
	if err != nil {
		logger.Println("Error preparing statement:", err)
		return
	}
	defer decisionsStmt.Close()

	rows, err := decisionsStmt.Queryx(page - 1)
	if err != nil {
		logger.Printf("Error loading motions for page %d: %v\n", page, err)
		return
	}
	defer rows.Close()

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

func FindVotersUnvotedDecisionsForDisplayOnPage(page int64, voter *Voter) (decisions []*DecisionForDisplay, err error) {
	decisionsStmt, err := db.Preparex(sqlListUnvotedDecisions)
	if err != nil {
		logger.Println("Error preparing statement:", err)
		return
	}
	defer decisionsStmt.Close()

	rows, err := decisionsStmt.Queryx(page - 1, voter.Id)
	if err != nil {
		logger.Printf("Error loading motions for page %d: %v\n", page, err)
		return
	}
	defer rows.Close()

	for rows.Next() {
		var d DecisionForDisplay
		if err = rows.StructScan(&d); err != nil {
			logger.Printf("Error loading motions for page %d: %v\n", 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, err := db.Preparex(sqlVoteCount)
	if err != nil {
		logger.Println("Error preparing statement:", err)
		return
	}
	defer votesStmt.Close()

	voteRows, err := votesStmt.Queryx(d.Id)
	if err != nil {
		logger.Printf("Error fetching vote sums for motion %s: %v\n", 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 {
			logger.Printf("Error fetching vote sums for motion %s: %v\n", 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, err := db.Preparex(sqlGetVotesForDecision)
	if err != nil {
		logger.Println("Error preparing statement:", err)
		return
	}
	defer votesStmt.Close()
	err = votesStmt.Select(&d.Votes, d.Id)
	if err != nil {
		logger.Printf("Error selecting votes for motion %s: %v\n", d.Tag, err)
	}
	return
}

func (d *Decision) OlderExists() (result bool, err error) {
	olderStmt, err := db.Preparex(sqlCountOlderThanDecision)
	if err != nil {
		logger.Println("Error preparing statement:", err)
		return
	}
	defer olderStmt.Close()

	if err := olderStmt.Get(&result, d.Proposed); err != nil {
		logger.Printf("Error finding older motions than %s: %v\n", d.Tag, err)
	}
	return
}

func FindVoterByAddress(emailAddress string) (voter *Voter, err error) {
	findVoterStmt, err := db.Preparex(sqlGetVoter)
	if err != nil {
		logger.Println("Error preparing statement:", err)
		return
	}
	defer findVoterStmt.Close()

	voter = &Voter{}
	if err = findVoterStmt.Get(voter, emailAddress); err != nil {
		if err != sql.ErrNoRows {
			logger.Printf("Error getting voter for address %s: %v\n", emailAddress, err)
		} else {
			err = nil
			voter = nil
		}
	}
	return
}