package db

import (
	"context"
	"time"

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

// ScheduleStatus represents the current status of a fixture schedule proposal
type ScheduleStatus string

const (
	ScheduleStatusPending     ScheduleStatus = "pending"
	ScheduleStatusAccepted    ScheduleStatus = "accepted"
	ScheduleStatusRejected    ScheduleStatus = "rejected"
	ScheduleStatusRescheduled ScheduleStatus = "rescheduled"
	ScheduleStatusPostponed   ScheduleStatus = "postponed"
	ScheduleStatusCancelled   ScheduleStatus = "cancelled"
	ScheduleStatusWithdrawn   ScheduleStatus = "withdrawn"
)

// IsTerminal returns true if the status is a terminal (immutable) state
func (s ScheduleStatus) IsTerminal() bool {
	switch s {
	case ScheduleStatusRejected, ScheduleStatusRescheduled,
		ScheduleStatusPostponed, ScheduleStatusCancelled,
		ScheduleStatusWithdrawn:
		return true
	}
	return false
}

// RescheduleReason represents the predefined reasons for rescheduling or postponing
type RescheduleReason string

const (
	ReasonMutuallyAgreed  RescheduleReason = "Mutually Agreed"
	ReasonTeamUnavailable RescheduleReason = "Team Unavailable"
	ReasonTeamNoShow      RescheduleReason = "Team No-show"
)

type FixtureSchedule struct {
	bun.BaseModel `bun:"table:fixture_schedules,alias:fs"`

	ID               int            `bun:"id,pk,autoincrement"`
	FixtureID        int            `bun:",notnull"`
	ScheduledTime    *time.Time     `bun:"scheduled_time"`
	ProposedByTeamID int            `bun:",notnull"`
	AcceptedByTeamID *int           `bun:"accepted_by_team_id"`
	Status           ScheduleStatus `bun:",notnull,default:'pending'"`
	RescheduleReason *string        `bun:"reschedule_reason"`
	CreatedAt        int64          `bun:",notnull"`
	UpdatedAt        *int64         `bun:"updated_at"`

	Fixture    *Fixture `bun:"rel:belongs-to,join:fixture_id=id"`
	ProposedBy *Team    `bun:"rel:belongs-to,join:proposed_by_team_id=id"`
	AcceptedBy *Team    `bun:"rel:belongs-to,join:accepted_by_team_id=id"`
}

// GetAcceptedSchedulesForFixtures returns the accepted schedule for each fixture in the given list.
// Returns a map of fixtureID -> *FixtureSchedule (only accepted schedules are included).
func GetAcceptedSchedulesForFixtures(ctx context.Context, tx bun.Tx, fixtureIDs []int) (map[int]*FixtureSchedule, error) {
	if len(fixtureIDs) == 0 {
		return map[int]*FixtureSchedule{}, nil
	}
	schedules, err := GetList[FixtureSchedule](tx).
		Where("fixture_id IN (?)", bun.In(fixtureIDs)).
		Where("status = ?", ScheduleStatusAccepted).
		GetAll(ctx)
	if err != nil {
		return nil, errors.Wrap(err, "GetList")
	}
	result := make(map[int]*FixtureSchedule, len(schedules))
	for _, s := range schedules {
		// If multiple accepted exist (shouldn't happen), keep the most recent
		existing, ok := result[s.FixtureID]
		if !ok || s.CreatedAt > existing.CreatedAt {
			result[s.FixtureID] = s
		}
	}
	return result, nil
}

// GetFixtureScheduleHistory returns all schedule records for a fixture in chronological order
func GetFixtureScheduleHistory(ctx context.Context, tx bun.Tx, fixtureID int) ([]*FixtureSchedule, error) {
	schedules, err := GetList[FixtureSchedule](tx).
		Where("fixture_id = ?", fixtureID).
		Order("created_at ASC", "id ASC").
		Relation("ProposedBy").
		Relation("AcceptedBy").
		GetAll(ctx)
	if err != nil {
		return nil, errors.Wrap(err, "GetList")
	}
	return schedules, nil
}

// GetCurrentFixtureSchedule returns the most recent schedule record for a fixture.
// Returns nil, nil if no schedule exists.
func GetCurrentFixtureSchedule(ctx context.Context, tx bun.Tx, fixtureID int) (*FixtureSchedule, error) {
	schedule := new(FixtureSchedule)
	err := tx.NewSelect().
		Model(schedule).
		Where("fixture_id = ?", fixtureID).
		Order("created_at DESC", "id DESC").
		Relation("ProposedBy").
		Relation("AcceptedBy").
		Limit(1).
		Scan(ctx)
	if err != nil {
		if err.Error() == "sql: no rows in result set" {
			return nil, nil
		}
		return nil, errors.Wrap(err, "tx.NewSelect")
	}
	return schedule, nil
}

// ProposeFixtureSchedule creates a new pending schedule proposal for a fixture.
// If there is an existing pending record with no time (postponed placeholder), it will be
// superseded. Cannot propose on cancelled or accepted schedules.
func ProposeFixtureSchedule(
	ctx context.Context,
	tx bun.Tx,
	fixtureID, proposedByTeamID int,
	scheduledTime time.Time,
	audit *AuditMeta,
) (*FixtureSchedule, error) {
	current, err := GetCurrentFixtureSchedule(ctx, tx, fixtureID)
	if err != nil {
		return nil, errors.Wrap(err, "GetCurrentFixtureSchedule")
	}
	if current != nil {
		switch current.Status {
		case ScheduleStatusCancelled:
			return nil, BadRequest("cannot propose a new time for a cancelled fixture")
		case ScheduleStatusAccepted:
			return nil, BadRequest("fixture already has an accepted schedule; use reschedule instead")
		case ScheduleStatusPending:
			// Supersede existing pending record (e.g., postponed placeholder or old proposal)
			now := time.Now().Unix()
			current.Status = ScheduleStatusRescheduled
			current.UpdatedAt = &now
			err = UpdateByID(tx, current.ID, current).
				Column("status", "updated_at").
				Exec(ctx)
			if err != nil {
				return nil, errors.Wrap(err, "UpdateByID")
			}
			// rejected, rescheduled, postponed are terminal — safe to create a new proposal
		}
	}

	schedule := &FixtureSchedule{
		FixtureID:        fixtureID,
		ScheduledTime:    &scheduledTime,
		ProposedByTeamID: proposedByTeamID,
		Status:           ScheduleStatusPending,
		CreatedAt:        time.Now().Unix(),
	}
	err = Insert(tx, schedule).WithAudit(audit, &AuditInfo{
		Action:       "fixture_schedule.propose",
		ResourceType: "fixture_schedule",
		ResourceID:   fixtureID,
		Details: map[string]any{
			"fixture_id":     fixtureID,
			"proposed_by":    proposedByTeamID,
			"scheduled_time": scheduledTime,
		},
	}).Exec(ctx)
	if err != nil {
		return nil, errors.Wrap(err, "Insert")
	}
	return schedule, nil
}

// AcceptFixtureSchedule accepts a pending schedule proposal.
// The acceptedByTeamID must be the other team (not the proposer).
func AcceptFixtureSchedule(
	ctx context.Context,
	tx bun.Tx,
	scheduleID, acceptedByTeamID int,
	audit *AuditMeta,
) error {
	schedule, err := GetByID[FixtureSchedule](tx, scheduleID).Get(ctx)
	if err != nil {
		return errors.Wrap(err, "GetByID")
	}
	if schedule.Status != ScheduleStatusPending {
		return BadRequest("schedule is not in pending status")
	}
	if schedule.ProposedByTeamID == acceptedByTeamID {
		return BadRequest("cannot accept your own proposal")
	}

	now := time.Now().Unix()
	schedule.AcceptedByTeamID = &acceptedByTeamID
	schedule.Status = ScheduleStatusAccepted
	schedule.UpdatedAt = &now
	err = UpdateByID(tx, schedule.ID, schedule).
		Column("accepted_by_team_id", "status", "updated_at").
		WithAudit(audit, &AuditInfo{
			Action:       "fixture_schedule.accept",
			ResourceType: "fixture_schedule",
			ResourceID:   scheduleID,
			Details: map[string]any{
				"fixture_id":  schedule.FixtureID,
				"accepted_by": acceptedByTeamID,
			},
		}).Exec(ctx)
	if err != nil {
		return errors.Wrap(err, "UpdateByID")
	}
	return nil
}

// RejectFixtureSchedule rejects a pending schedule proposal.
func RejectFixtureSchedule(
	ctx context.Context,
	tx bun.Tx,
	scheduleID int,
	audit *AuditMeta,
) error {
	schedule, err := GetByID[FixtureSchedule](tx, scheduleID).Get(ctx)
	if err != nil {
		return errors.Wrap(err, "GetByID")
	}
	if schedule.Status != ScheduleStatusPending {
		return BadRequest("schedule is not in pending status")
	}

	now := time.Now().Unix()
	schedule.Status = ScheduleStatusRejected
	schedule.UpdatedAt = &now
	err = UpdateByID(tx, schedule.ID, schedule).
		Column("status", "updated_at").
		WithAudit(audit, &AuditInfo{
			Action:       "fixture_schedule.reject",
			ResourceType: "fixture_schedule",
			ResourceID:   scheduleID,
			Details: map[string]any{
				"fixture_id": schedule.FixtureID,
			},
		}).Exec(ctx)
	if err != nil {
		return errors.Wrap(err, "UpdateByID")
	}
	return nil
}

// RescheduleFixtureSchedule marks the current accepted schedule as rescheduled and creates
// a new pending proposal with the new time.
func RescheduleFixtureSchedule(
	ctx context.Context,
	tx bun.Tx,
	fixtureID, proposedByTeamID int,
	newTime time.Time,
	reason string,
	audit *AuditMeta,
) (*FixtureSchedule, error) {
	current, err := GetCurrentFixtureSchedule(ctx, tx, fixtureID)
	if err != nil {
		return nil, errors.Wrap(err, "GetCurrentFixtureSchedule")
	}
	if current == nil || current.Status != ScheduleStatusAccepted {
		return nil, BadRequest("no accepted schedule to reschedule")
	}

	now := time.Now().Unix()
	current.Status = ScheduleStatusRescheduled
	current.RescheduleReason = &reason
	current.UpdatedAt = &now
	err = UpdateByID(tx, current.ID, current).
		Column("status", "reschedule_reason", "updated_at").
		Exec(ctx)
	if err != nil {
		return nil, errors.Wrap(err, "UpdateByID")
	}

	// Create new pending proposal
	schedule := &FixtureSchedule{
		FixtureID:        fixtureID,
		ScheduledTime:    &newTime,
		ProposedByTeamID: proposedByTeamID,
		Status:           ScheduleStatusPending,
		CreatedAt:        time.Now().Unix(),
	}
	err = Insert(tx, schedule).WithAudit(audit, &AuditInfo{
		Action:       "fixture_schedule.reschedule",
		ResourceType: "fixture_schedule",
		ResourceID:   fixtureID,
		Details: map[string]any{
			"fixture_id":      fixtureID,
			"proposed_by":     proposedByTeamID,
			"new_time":        newTime,
			"reason":          reason,
			"old_schedule_id": current.ID,
		},
	}).Exec(ctx)
	if err != nil {
		return nil, errors.Wrap(err, "Insert")
	}
	return schedule, nil
}

// PostponeFixtureSchedule marks the current accepted schedule as postponed.
// This is a terminal state — a new proposal can be created afterwards.
func PostponeFixtureSchedule(
	ctx context.Context,
	tx bun.Tx,
	fixtureID int,
	reason string,
	audit *AuditMeta,
) error {
	current, err := GetCurrentFixtureSchedule(ctx, tx, fixtureID)
	if err != nil {
		return errors.Wrap(err, "GetCurrentFixtureSchedule")
	}
	if current == nil || current.Status != ScheduleStatusAccepted {
		return BadRequest("no accepted schedule to postpone")
	}

	now := time.Now().Unix()
	current.Status = ScheduleStatusPostponed
	current.RescheduleReason = &reason
	current.UpdatedAt = &now
	err = UpdateByID(tx, current.ID, current).
		Column("status", "reschedule_reason", "updated_at").
		WithAudit(audit, &AuditInfo{
			Action:       "fixture_schedule.postpone",
			ResourceType: "fixture_schedule",
			ResourceID:   fixtureID,
			Details: map[string]any{
				"fixture_id":      fixtureID,
				"reason":          reason,
				"old_schedule_id": current.ID,
			},
		}).Exec(ctx)
	if err != nil {
		return errors.Wrap(err, "UpdateByID")
	}
	return nil
}

// WithdrawFixtureSchedule allows the proposer to withdraw their pending proposal.
// Only the team that proposed can withdraw it.
func WithdrawFixtureSchedule(
	ctx context.Context,
	tx bun.Tx,
	scheduleID, withdrawByTeamID int,
	audit *AuditMeta,
) error {
	schedule, err := GetByID[FixtureSchedule](tx, scheduleID).Get(ctx)
	if err != nil {
		return errors.Wrap(err, "GetByID")
	}
	if schedule.Status != ScheduleStatusPending {
		return BadRequest("schedule is not in pending status")
	}
	if schedule.ProposedByTeamID != withdrawByTeamID {
		return BadRequest("only the proposing team can withdraw their proposal")
	}

	now := time.Now().Unix()
	schedule.Status = ScheduleStatusWithdrawn
	schedule.UpdatedAt = &now
	err = UpdateByID(tx, schedule.ID, schedule).
		Column("status", "updated_at").
		WithAudit(audit, &AuditInfo{
			Action:       "fixture_schedule.withdraw",
			ResourceType: "fixture_schedule",
			ResourceID:   scheduleID,
			Details: map[string]any{
				"fixture_id":   schedule.FixtureID,
				"withdrawn_by": withdrawByTeamID,
			},
		}).Exec(ctx)
	if err != nil {
		return errors.Wrap(err, "UpdateByID")
	}
	return nil
}

// CancelFixtureSchedule marks the current schedule as cancelled. This is a terminal state.
// Requires fixtures.manage permission (moderator-level).
func CancelFixtureSchedule(
	ctx context.Context,
	tx bun.Tx,
	fixtureID int,
	reason string,
	audit *AuditMeta,
) error {
	current, err := GetCurrentFixtureSchedule(ctx, tx, fixtureID)
	if err != nil {
		return errors.Wrap(err, "GetCurrentFixtureSchedule")
	}
	if current == nil {
		return BadRequest("no schedule to cancel")
	}
	if current.Status.IsTerminal() {
		return BadRequest("schedule is already in a terminal state")
	}

	now := time.Now().Unix()
	current.Status = ScheduleStatusCancelled
	current.RescheduleReason = &reason
	current.UpdatedAt = &now
	err = UpdateByID(tx, current.ID, current).
		Column("status", "reschedule_reason", "updated_at").
		WithAudit(audit, &AuditInfo{
			Action:       "fixture_schedule.cancel",
			ResourceType: "fixture_schedule",
			ResourceID:   fixtureID,
			Details: map[string]any{
				"fixture_id":  fixtureID,
				"reason":      reason,
				"schedule_id": current.ID,
			},
		}).Exec(ctx)
	if err != nil {
		return errors.Wrap(err, "UpdateByID")
	}
	return nil
}