package db

import (
	"context"
	"fmt"
	"strconv"
	"strings"
	"time"

	"github.com/pkg/errors"
	"github.com/uptrace/bun"
)

type Fixture struct {
	bun.BaseModel `bun:"table:fixtures,alias:f"`

	ID         int    `bun:"id,pk,autoincrement"`
	SeasonID   int    `bun:",notnull,unique:round"`
	LeagueID   int    `bun:",notnull,unique:round"`
	HomeTeamID int    `bun:",notnull,unique:round"`
	AwayTeamID int    `bun:",notnull,unique:round"`
	Round      int    `bun:"round,unique:round"`
	GameWeek   *int   `bun:"game_week"`
	CreatedAt  int64  `bun:"created_at,notnull"`
	UpdatedAt  *int64 `bun:"updated_at"`

	Season   *Season `bun:"rel:belongs-to,join:season_id=id"`
	League   *League `bun:"rel:belongs-to,join:league_id=id"`
	HomeTeam *Team   `bun:"rel:belongs-to,join:home_team_id=id"`
	AwayTeam *Team   `bun:"rel:belongs-to,join:away_team_id=id"`

	Schedules []*FixtureSchedule `bun:"rel:has-many,join:id=fixture_id"`
}

// CanSchedule checks if the user is a manager of one of the teams in the fixture.
// Returns (canSchedule, teamID) where teamID is the team the user manages (0 if not a manager).
func (f *Fixture) CanSchedule(ctx context.Context, tx bun.Tx, user *User) (bool, int, error) {
	if user == nil || user.Player == nil {
		return false, 0, nil
	}
	roster := new(TeamRoster)
	err := tx.NewSelect().
		Model(roster).
		Column("team_id", "is_manager").
		Where("team_id IN (?)", bun.In([]int{f.HomeTeamID, f.AwayTeamID})).
		Where("season_id = ?", f.SeasonID).
		Where("league_id = ?", f.LeagueID).
		Where("player_id = ?", user.Player.ID).
		Scan(ctx)
	if err != nil {
		if err.Error() == "sql: no rows in result set" {
			return false, 0, nil
		}
		return false, 0, errors.Wrap(err, "tx.NewSelect")
	}
	if !roster.IsManager {
		return false, 0, nil
	}
	return true, roster.TeamID, nil
}

func NewFixture(ctx context.Context, tx bun.Tx, seasonShortName, leagueShortName string,
	homeTeamID, awayTeamID, round int, audit *AuditMeta,
) (*Fixture, error) {
	season, league, teams, err := GetSeasonLeagueWithTeams(ctx, tx, seasonShortName, leagueShortName)
	if err != nil {
		return nil, errors.Wrap(err, "GetSeasonLeague")
	}
	homeTeam, err := GetTeam(ctx, tx, homeTeamID)
	if err != nil {
		return nil, errors.Wrap(err, "GetTeam")
	}
	awayTeam, err := GetTeam(ctx, tx, awayTeamID)
	if err != nil {
		return nil, errors.Wrap(err, "GetTeam")
	}
	if err = checkTeamsAssociated(season, league, teams, []*Team{homeTeam, awayTeam}); err != nil {
		return nil, errors.Wrap(err, "checkTeamsAssociated")
	}
	fixture := newFixture(season, league, homeTeam, awayTeam, round, time.Now())
	err = Insert(tx, fixture).WithAudit(audit, nil).Exec(ctx)
	if err != nil {
		return nil, errors.Wrap(err, "Insert")
	}
	return fixture, nil
}

func NewRound(ctx context.Context, tx bun.Tx, seasonShortName, leagueShortName string,
	round int, audit *AuditMeta,
) ([]*Fixture, error) {
	season, league, teams, err := GetSeasonLeagueWithTeams(ctx, tx, seasonShortName, leagueShortName)
	if err != nil {
		return nil, errors.Wrap(err, "GetSeasonLeague")
	}
	fixtures := generateRound(season, league, round, teams)
	err = InsertMultiple(tx, fixtures).WithAudit(audit, nil).Exec(ctx)
	if err != nil {
		return nil, errors.Wrap(err, "InsertMultiple")
	}
	return fixtures, nil
}

func GetFixtures(ctx context.Context, tx bun.Tx, seasonShortName, leagueShortName string) (*SeasonLeague, []*Fixture, error) {
	sl, err := GetSeasonLeague(ctx, tx, seasonShortName, leagueShortName)
	if err != nil {
		return nil, nil, errors.Wrap(err, "GetSeasonLeague")
	}
	fixtures, err := GetList[Fixture](tx).
		Where("season_id = ?", sl.SeasonID).
		Where("league_id = ?", sl.LeagueID).
		Order("game_week ASC NULLS FIRST", "round ASC", "id ASC").
		Relation("HomeTeam").
		Relation("AwayTeam").
		GetAll(ctx)
	if err != nil {
		return nil, nil, errors.Wrap(err, "GetList")
	}
	return sl, fixtures, nil
}

func GetFixture(ctx context.Context, tx bun.Tx, id int) (*Fixture, error) {
	return GetByID[Fixture](tx, id).
		Relation("Season").
		Relation("League").
		Relation("HomeTeam").
		Relation("AwayTeam").
		Get(ctx)
}

// GetAllocatedFixtures returns all fixtures with a game_week assigned for a season+league.
func GetAllocatedFixtures(ctx context.Context, tx bun.Tx, seasonID, leagueID int) ([]*Fixture, error) {
	fixtures, err := GetList[Fixture](tx).
		Where("season_id = ?", seasonID).
		Where("league_id = ?", leagueID).
		Where("game_week IS NOT NULL").
		Order("game_week ASC", "round ASC", "id ASC").
		Relation("HomeTeam").
		Relation("AwayTeam").
		GetAll(ctx)
	if err != nil {
		return nil, errors.Wrap(err, "GetList")
	}
	return fixtures, nil
}

func GetFixturesForTeam(ctx context.Context, tx bun.Tx, seasonID, leagueID, teamID int) ([]*Fixture, error) {
	fixtures, err := GetList[Fixture](tx).
		Where("season_id = ?", seasonID).
		Where("league_id = ?", leagueID).
		Where("game_week IS NOT NULL").
		Where("(home_team_id = ? OR away_team_id = ?)", teamID, teamID).
		Order("game_week ASC", "round ASC", "id ASC").
		Relation("HomeTeam").
		Relation("AwayTeam").
		GetAll(ctx)
	if err != nil {
		return nil, errors.Wrap(err, "GetList")
	}
	return fixtures, nil
}

func GetFixturesByGameWeek(ctx context.Context, tx bun.Tx, seasonID, leagueID, gameweek int) ([]*Fixture, error) {
	fixtures, err := GetList[Fixture](tx).
		Where("season_id = ?", seasonID).
		Where("league_id = ?", leagueID).
		Where("game_week = ?", gameweek).
		Order("round ASC", "id ASC").
		Relation("HomeTeam").
		Relation("AwayTeam").
		GetAll(ctx)
	if err != nil {
		return nil, errors.Wrap(err, "GetList")
	}
	return fixtures, nil
}

func GetUnallocatedFixtures(ctx context.Context, tx bun.Tx, seasonID, leagueID int) ([]*Fixture, error) {
	fixtures, err := GetList[Fixture](tx).
		Where("season_id = ?", seasonID).
		Where("league_id = ?", leagueID).
		Where("game_week IS NULL").
		Order("round ASC", "id ASC").
		Relation("HomeTeam").
		Relation("AwayTeam").
		GetAll(ctx)
	if err != nil {
		return nil, errors.Wrap(err, "GetList")
	}
	return fixtures, nil
}

func CountUnallocatedFixtures(ctx context.Context, tx bun.Tx, seasonID, leagueID int) (int, error) {
	count, err := GetList[Fixture](tx).
		Where("season_id = ?", seasonID).
		Where("league_id = ?", leagueID).
		Where("game_week IS NULL").
		Count(ctx)
	if err != nil {
		return 0, errors.Wrap(err, "GetList")
	}
	return count, nil
}

func GetMaxGameWeek(ctx context.Context, tx bun.Tx, seasonID, leagueID int) (int, error) {
	var maxGameWeek int
	err := tx.NewSelect().
		Model((*Fixture)(nil)).
		Column("game_week").
		Where("season_id = ?", seasonID).
		Where("league_id = ?", leagueID).
		Order("game_week DESC NULLS LAST").
		Limit(1).Scan(ctx, &maxGameWeek)
	if err != nil {
		return 0, errors.Wrap(err, "tx.NewSelect")
	}
	return maxGameWeek, nil
}

func UpdateFixtureGameWeeks(ctx context.Context, tx bun.Tx, fixtures []*Fixture, audit *AuditMeta) error {
	details := []any{}
	for _, fixture := range fixtures {
		err := UpdateByID(tx, fixture.ID, fixture).
			Column("game_week").
			Exec(ctx)
		if err != nil {
			return errors.Wrap(err, "UpdateByID")
		}
		details = append(details, map[string]any{"fixture_id": fixture.ID, "game_week": fixture.GameWeek})
	}
	info := &AuditInfo{
		"fixtures.manage",
		"fixture",
		"multiple",
		map[string]any{"updated": details},
	}
	err := LogSuccess(ctx, tx, audit, info)
	if err != nil {
		return errors.Wrap(err, "LogSuccess")
	}
	return nil
}

func DeleteAllFixtures(ctx context.Context, tx bun.Tx, seasonShortName, leagueShortName string, audit *AuditMeta) error {
	sl, err := GetSeasonLeague(ctx, tx, seasonShortName, leagueShortName)
	if err != nil {
		return errors.Wrap(err, "GetSeasonLeague")
	}
	err = DeleteItem[Fixture](tx).
		Where("season_id = ?", sl.SeasonID).
		Where("league_id = ?", sl.LeagueID).
		WithAudit(audit, nil).
		Delete(ctx)
	if err != nil {
		return errors.Wrap(err, "DeleteItem")
	}
	return nil
}

func DeleteFixture(ctx context.Context, tx bun.Tx, id int, audit *AuditMeta) error {
	err := DeleteByID[Fixture](tx, id).
		WithAudit(audit, nil).
		Delete(ctx)
	if err != nil {
		return errors.Wrap(err, "DeleteByID")
	}
	return nil
}

func newFixture(season *Season, league *League, homeTeam, awayTeam *Team, round int, created time.Time) *Fixture {
	return &Fixture{
		SeasonID:   season.ID,
		LeagueID:   league.ID,
		HomeTeamID: homeTeam.ID,
		AwayTeamID: awayTeam.ID,
		Round:      round,
		CreatedAt:  created.Unix(),
	}
}

func checkTeamsAssociated(season *Season, league *League, teamsIn []*Team, toCheck []*Team) error {
	badIDs := []string{}
	master := map[int]bool{}
	for _, team := range teamsIn {
		master[team.ID] = true
	}
	for _, team := range toCheck {
		if !master[team.ID] {
			badIDs = append(badIDs, strconv.Itoa(team.ID))
		}
	}
	ids := strings.Join(badIDs, ",")
	if len(ids) > 0 {
		return BadRequestNotAssociated("season_league", "team",
			"season_id,league_id", "ids",
			fmt.Sprintf("%v,%v", season.ID, league.ID),
			ids)
	}
	return nil
}

type versus struct {
	homeTeam *Team
	awayTeam *Team
}

func generateRound(season *Season, league *League, round int, teams []*Team) []*Fixture {
	now := time.Now()
	numTeams := len(teams)
	numGames := numTeams * (numTeams - 1) / 2
	fixtures := make([]*Fixture, numGames)
	for i, matchup := range allTeamsPlay(teams, round) {
		fixtures[i] = newFixture(season, league, matchup.homeTeam, matchup.awayTeam, round, now)
	}
	return fixtures
}

func allTeamsPlay(teams []*Team, round int) []*versus {
	matchups := []*versus{}
	if len(teams) < 2 {
		return matchups
	}
	team1 := teams[0]
	teams = teams[1:]
	matchups = append(matchups, playOtherTeams(team1, teams, round)...)
	matchups = append(matchups, allTeamsPlay(teams, round)...)
	return matchups
}

func playOtherTeams(team *Team, teams []*Team, round int) []*versus {
	matchups := make([]*versus, len(teams))
	for i, opponent := range teams {
		versus := &versus{}
		if (i+round)%2 == 0 {
			versus.homeTeam = team
			versus.awayTeam = opponent
		} else {
			versus.homeTeam = opponent
			versus.awayTeam = team
		}
		matchups[i] = versus
	}
	return matchups
}

func AutoAllocateFixtures(fixtures []*Fixture, gamesPerWeek, startingWeek int) []*Fixture {
	gameWeek := startingWeek
	teamPlays := map[int]int{}
	// Work on a copy so we can track what's remaining
	remaining := make([]*Fixture, len(fixtures))
	copy(remaining, fixtures)
	for len(remaining) > 0 {
		madeProgress := false
		nextRemaining := make([]*Fixture, 0, len(remaining))
		for _, fixture := range remaining {
			if teamPlays[fixture.HomeTeamID] < gamesPerWeek &&
				teamPlays[fixture.AwayTeamID] < gamesPerWeek {
				gw := gameWeek
				fixture.GameWeek = &gw
				teamPlays[fixture.HomeTeamID]++
				teamPlays[fixture.AwayTeamID]++
				madeProgress = true
			} else {
				nextRemaining = append(nextRemaining, fixture)
			}
		}
		if !madeProgress {
			// No fixture could be placed this week — advance to avoid infinite loop
			// (shouldn't happen with valid fixture data, but guards against edge cases)
			gameWeek++
			teamPlays = map[int]int{}
			continue
		}
		remaining = nextRemaining
		if len(remaining) > 0 {
			gameWeek++
			teamPlays = map[int]int{}
		}
	}
	return fixtures
}