package policy

import (
	"context"
	"errors"

	"github.com/google/uuid"
	"github.com/jackc/pgx/v5/pgxpool"
)

type Repository interface {
	List(ctx context.Context) ([]Policy, error)
	Create(ctx context.Context, input CreateRequest, createdBy uuid.UUID) (Policy, error)
	Update(ctx context.Context, policyID uuid.UUID, input UpdateRequest) (Policy, error)
	Delete(ctx context.Context, policyID uuid.UUID) error
	ResolveDestinations(ctx context.Context, userID uuid.UUID, deviceID *uuid.UUID) ([]string, error)
}

type PGRepository struct {
	db *pgxpool.Pool
}

func NewPGRepository(db *pgxpool.Pool) *PGRepository {
	return &PGRepository{db: db}
}

func (r *PGRepository) List(ctx context.Context) ([]Policy, error) {
	rows, err := r.db.Query(ctx, `
		select
			p.id,
			p.name,
			p.description,
			p.priority,
			p.effect,
			p.full_tunnel,
			p.is_active,
			coalesce(array_agg(pd.destination::text) filter (where pd.destination is not null), '{}')
		from policies p
		left join policy_destinations pd on pd.policy_id = p.id
		where p.deleted_at is null
		group by p.id, p.name, p.description, p.priority, p.effect, p.full_tunnel, p.is_active, p.created_at
		order by p.priority asc, p.created_at desc
	`)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var items []Policy
	for rows.Next() {
		var item Policy
		if err := rows.Scan(&item.ID, &item.Name, &item.Description, &item.Priority, &item.Effect, &item.FullTunnel, &item.IsActive, &item.Destinations); err != nil {
			return nil, err
		}
		targets, err := r.listTargets(ctx, item.ID)
		if err != nil {
			return nil, err
		}
		item.Targets = targets
		items = append(items, item)
	}
	return items, rows.Err()
}

func (r *PGRepository) Create(ctx context.Context, input CreateRequest, createdBy uuid.UUID) (Policy, error) {
	tx, err := r.db.Begin(ctx)
	if err != nil {
		return Policy{}, err
	}
	defer tx.Rollback(ctx)

	policyID := uuid.New()
	_, err = tx.Exec(ctx, `
		insert into policies (id, name, description, priority, effect, full_tunnel, created_by)
		values ($1, $2, $3, $4, $5, $6, $7)
	`, policyID, input.Name, input.Description, input.Priority, input.Effect, input.FullTunnel, createdBy)
	if err != nil {
		return Policy{}, err
	}

	for _, destination := range input.Destinations {
		if _, err := tx.Exec(ctx, `
			insert into policy_destinations (id, policy_id, destination)
			values ($1, $2, $3::cidr)
		`, uuid.New(), policyID, destination); err != nil {
			return Policy{}, err
		}
	}

	for _, target := range input.Targets {
		if _, err := tx.Exec(ctx, `
			insert into policy_targets (id, policy_id, target_type, target_id)
			values ($1, $2, $3, $4)
		`, uuid.New(), policyID, target.Type, target.ID); err != nil {
			return Policy{}, err
		}
	}

	if err := tx.Commit(ctx); err != nil {
		return Policy{}, err
	}

	return r.getByID(ctx, policyID)
}

func (r *PGRepository) Update(ctx context.Context, policyID uuid.UUID, input UpdateRequest) (Policy, error) {
	tx, err := r.db.Begin(ctx)
	if err != nil {
		return Policy{}, err
	}
	defer tx.Rollback(ctx)

	_, err = tx.Exec(ctx, `
		update policies
		set
			name = coalesce($2, name),
			description = coalesce($3, description),
			priority = coalesce($4, priority),
			effect = coalesce($5, effect),
			full_tunnel = coalesce($6, full_tunnel),
			is_active = coalesce($7, is_active),
			updated_at = now()
		where id = $1 and deleted_at is null
	`, policyID, input.Name, input.Description, input.Priority, input.Effect, input.FullTunnel, input.IsActive)
	if err != nil {
		return Policy{}, err
	}

	if input.Destinations != nil {
		if _, err := tx.Exec(ctx, `delete from policy_destinations where policy_id = $1`, policyID); err != nil {
			return Policy{}, err
		}
		for _, destination := range input.Destinations {
			if _, err := tx.Exec(ctx, `
				insert into policy_destinations (id, policy_id, destination)
				values ($1, $2, $3::cidr)
			`, uuid.New(), policyID, destination); err != nil {
				return Policy{}, err
			}
		}
	}

	if input.Targets != nil {
		if _, err := tx.Exec(ctx, `delete from policy_targets where policy_id = $1`, policyID); err != nil {
			return Policy{}, err
		}
		for _, target := range input.Targets {
			if _, err := tx.Exec(ctx, `
				insert into policy_targets (id, policy_id, target_type, target_id)
				values ($1, $2, $3, $4)
			`, uuid.New(), policyID, target.Type, target.ID); err != nil {
				return Policy{}, err
			}
		}
	}

	if err := tx.Commit(ctx); err != nil {
		return Policy{}, err
	}

	return r.getByID(ctx, policyID)
}

func (r *PGRepository) Delete(ctx context.Context, policyID uuid.UUID) error {
	_, err := r.db.Exec(ctx, `update policies set deleted_at = now(), updated_at = now() where id = $1 and deleted_at is null`, policyID)
	return err
}

func (r *PGRepository) ResolveDestinations(ctx context.Context, userID uuid.UUID, deviceID *uuid.UUID) ([]string, error) {
	query := `
		select distinct pd.destination::text
		from policies p
		join policy_destinations pd on pd.policy_id = p.id
		join policy_targets pt on pt.policy_id = p.id
		where p.deleted_at is null
		  and p.is_active = true
		  and p.effect = 'allow'
		  and (
			(pt.target_type = 'user' and pt.target_id = $1)
			or (pt.target_type = 'group' and exists (
				select 1 from group_memberships gm
				where gm.group_id = pt.target_id and gm.user_id = $1
			))
	`
	args := []any{userID}
	if deviceID != nil {
		query += ` or (pt.target_type = 'device' and pt.target_id = $2)`
		args = append(args, *deviceID)
	}
	query += `)`

	rows, err := r.db.Query(ctx, query, args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var destinations []string
	for rows.Next() {
		var value string
		if err := rows.Scan(&value); err != nil {
			return nil, err
		}
		destinations = append(destinations, value)
	}
	return destinations, rows.Err()
}

func (r *PGRepository) getByID(ctx context.Context, policyID uuid.UUID) (Policy, error) {
	items, err := r.List(ctx)
	if err != nil {
		return Policy{}, err
	}
	for _, item := range items {
		if item.ID == policyID {
			return item, nil
		}
	}
	return Policy{}, errors.New("policy not found")
}

func (r *PGRepository) listTargets(ctx context.Context, policyID uuid.UUID) ([]Target, error) {
	rows, err := r.db.Query(ctx, `
		select
			pt.target_type,
			pt.target_id,
			coalesce(u.username, g.name, d.name, '')
		from policy_targets pt
		left join users u on pt.target_type = 'user' and u.id = pt.target_id and u.deleted_at is null
		left join groups g on pt.target_type = 'group' and g.id = pt.target_id and g.deleted_at is null
		left join devices d on pt.target_type = 'device' and d.id = pt.target_id and d.deleted_at is null
		where pt.policy_id = $1
		order by pt.created_at asc
	`, policyID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var items []Target
	for rows.Next() {
		var item Target
		if err := rows.Scan(&item.Type, &item.ID, &item.Name); err != nil {
			return nil, err
		}
		items = append(items, item)
	}

	return items, rows.Err()
}
