package storage

import (
	"context"
	"database/sql"
	"fmt"
	"log"
	"os"
	"time"
)

// Group represents a lab group
type Group struct {
	ID          string    `json:"id"`
	Name        string    `json:"name"`
	Description string    `json:"description,omitempty"`
	CreatedAt   time.Time `json:"created_at"`
	CreatedBy   string    `json:"created_by"`
}

// GroupInvitation represents a pending invitation
type GroupInvitation struct {
	ID            string     `json:"id"`
	GroupID       string     `json:"group_id"`
	InvitedUserID string     `json:"invited_user_id"`
	InvitedBy     string     `json:"invited_by"`
	Status        string     `json:"status"`
	CreatedAt     time.Time  `json:"created_at"`
	ExpiresAt     *time.Time `json:"expires_at,omitempty"`
}

// CreateGroup creates a new lab group
func (db *DB) CreateGroup(name, description, createdBy string) (*Group, error) {
	id := fmt.Sprintf("group_%d", time.Now().UnixNano())

	var query string
	if db.dbType == DBTypeSQLite {
		query = `INSERT INTO groups (id, name, description, created_by) VALUES (?, ?, ?, ?)`
	} else {
		query = `INSERT INTO groups (id, name, description, created_by) VALUES ($1, $2, $3, $4)`
	}

	_, err := db.conn.ExecContext(context.Background(), query, id, name, description, createdBy)
	if err != nil {
		return nil, fmt.Errorf("failed to create group: %w", err)
	}

	// Add creator as admin
	if db.dbType == DBTypeSQLite {
		query = `INSERT INTO group_members (group_id, user_id, role) VALUES (?, ?, 'admin')`
	} else {
		query = `INSERT INTO group_members (group_id, user_id, role) VALUES ($1, $2, 'admin')`
	}
	_, err = db.conn.ExecContext(context.Background(), query, id, createdBy)
	if err != nil {
		return nil, fmt.Errorf("failed to add creator as admin: %w", err)
	}

	return &Group{
		ID:          id,
		Name:        name,
		Description: description,
		CreatedBy:   createdBy,
		CreatedAt:   time.Now(),
	}, nil
}

// ListGroupsForUser returns all groups the user is a member of
func (db *DB) ListGroupsForUser(userID string) ([]Group, error) {
	var query string
	if db.dbType == DBTypeSQLite {
		query = `
			SELECT g.id, g.name, g.description, g.created_at, g.created_by
			FROM groups g
			JOIN group_members gm ON gm.group_id = g.id
			WHERE gm.user_id = ?
			ORDER BY g.created_at DESC`
	} else {
		query = `
			SELECT g.id, g.name, g.description, g.created_at, g.created_by
			FROM groups g
			JOIN group_members gm ON gm.group_id = g.id
			WHERE gm.user_id = $1
			ORDER BY g.created_at DESC`
	}

	rows, err := db.conn.QueryContext(context.Background(), query, userID)
	if err != nil {
		return nil, fmt.Errorf("failed to list groups: %w", err)
	}
	defer func() {
		if err := rows.Close(); err != nil {
			log.Printf("ERROR: failed to close rows: %v", err)
		}
	}()

	var groups []Group
	for rows.Next() {
		var g Group
		var createdAt sql.NullTime
		err := rows.Scan(&g.ID, &g.Name, &g.Description, &createdAt, &g.CreatedBy)
		if err != nil {
			return nil, fmt.Errorf("failed to scan group: %w", err)
		}
		if createdAt.Valid {
			g.CreatedAt = createdAt.Time
		}
		groups = append(groups, g)
	}

	if err = rows.Err(); err != nil {
		return nil, fmt.Errorf("error iterating groups: %w", err)
	}

	return groups, nil
}

// IsGroupAdmin checks if user is an admin of the group
func (db *DB) IsGroupAdmin(userID, groupID string) (bool, error) {
	var query string
	if db.dbType == DBTypeSQLite {
		query = `SELECT COUNT(*) FROM group_members WHERE group_id = ? AND user_id = ? AND role = 'admin'`
	} else {
		query = `SELECT COUNT(*) FROM group_members WHERE group_id = $1 AND user_id = $2 AND role = 'admin'`
	}

	var count int
	err := db.conn.QueryRowContext(context.Background(), query, groupID, userID).Scan(&count)
	if err != nil {
		return false, fmt.Errorf("failed to check admin status: %w", err)
	}
	return count > 0, nil
}

// IsGroupMember checks if user is a member of the group
func (db *DB) IsGroupMember(userID, groupID string) (bool, error) {
	var query string
	if db.dbType == DBTypeSQLite {
		query = `SELECT COUNT(*) FROM group_members WHERE group_id = ? AND user_id = ?`
	} else {
		query = `SELECT COUNT(*) FROM group_members WHERE group_id = $1 AND user_id = $2`
	}

	var count int
	err := db.conn.QueryRowContext(context.Background(), query, groupID, userID).Scan(&count)
	if err != nil {
		return false, fmt.Errorf("failed to check membership: %w", err)
	}
	return count > 0, nil
}

// CreateGroupInvitation creates a new group invitation
func (db *DB) CreateGroupInvitation(groupID, invitedUserID, invitedBy string) (*GroupInvitation, error) {
	id := fmt.Sprintf("inv_%d", time.Now().UnixNano())
	expiresAt := time.Now().Add(7 * 24 * time.Hour) // 7 days

	var query string
	if db.dbType == DBTypeSQLite {
		query = `INSERT INTO group_invitations (id, group_id, invited_user_id, invited_by, expires_at) VALUES (?, ?, ?, ?, ?)`
	} else {
		query = `INSERT INTO group_invitations (id, group_id, invited_user_id, invited_by, expires_at) VALUES ($1, $2, $3, $4, $5)`
	}

	_, err := db.conn.ExecContext(context.Background(), query, id, groupID, invitedUserID, invitedBy, expiresAt)
	if err != nil {
		return nil, fmt.Errorf("failed to create invitation: %w", err)
	}

	return &GroupInvitation{
		ID:            id,
		GroupID:       groupID,
		InvitedUserID: invitedUserID,
		InvitedBy:     invitedBy,
		Status:        "pending",
		CreatedAt:     time.Now(),
		ExpiresAt:     &expiresAt,
	}, nil
}

// GetInvitation retrieves an invitation by ID
func (db *DB) GetInvitation(invitationID string) (*GroupInvitation, error) {
	var query string
	if db.dbType == DBTypeSQLite {
		query = `SELECT id, group_id, invited_user_id, invited_by, status, created_at, expires_at FROM group_invitations WHERE id = ?`
	} else {
		query = `SELECT id, group_id, invited_user_id, invited_by, status, created_at, expires_at FROM group_invitations WHERE id = $1`
	}

	var inv GroupInvitation
	var createdAt, expiresAt sql.NullTime
	err := db.conn.QueryRowContext(context.Background(), query, invitationID).Scan(
		&inv.ID, &inv.GroupID, &inv.InvitedUserID, &inv.InvitedBy, &inv.Status, &createdAt, &expiresAt,
	)
	if err != nil {
		if err == sql.ErrNoRows {
			return nil, fmt.Errorf("invitation not found")
		}
		return nil, fmt.Errorf("failed to get invitation: %w", err)
	}

	if createdAt.Valid {
		inv.CreatedAt = createdAt.Time
	}
	if expiresAt.Valid {
		inv.ExpiresAt = &expiresAt.Time
	}

	return &inv, nil
}

// ListPendingInvitationsForUser returns pending invitations for a user
func (db *DB) ListPendingInvitationsForUser(userID string) ([]GroupInvitation, error) {
	var query string
	if db.dbType == DBTypeSQLite {
		query = `
			SELECT id, group_id, invited_user_id, invited_by, status, created_at, expires_at
			FROM group_invitations
			WHERE invited_user_id = ? AND status = 'pending'
			ORDER BY created_at DESC`
	} else {
		query = `
			SELECT id, group_id, invited_user_id, invited_by, status, created_at, expires_at
			FROM group_invitations
			WHERE invited_user_id = $1 AND status = 'pending'
			ORDER BY created_at DESC`
	}

	rows, err := db.conn.QueryContext(context.Background(), query, userID)
	if err != nil {
		return nil, fmt.Errorf("failed to list invitations: %w", err)
	}
	defer func() {
		if err := rows.Close(); err != nil {
			log.Printf("ERROR: failed to close rows: %v", err)
		}
	}()

	var invitations []GroupInvitation
	for rows.Next() {
		var inv GroupInvitation
		var createdAt, expiresAt sql.NullTime
		err := rows.Scan(&inv.ID, &inv.GroupID, &inv.InvitedUserID, &inv.InvitedBy, &inv.Status, &createdAt, &expiresAt)
		if err != nil {
			return nil, fmt.Errorf("failed to scan invitation: %w", err)
		}
		if createdAt.Valid {
			inv.CreatedAt = createdAt.Time
		}
		if expiresAt.Valid {
			inv.ExpiresAt = &expiresAt.Time
		}
		invitations = append(invitations, inv)
	}

	if err = rows.Err(); err != nil {
		return nil, fmt.Errorf("error iterating invitations: %w", err)
	}

	return invitations, nil
}

// AcceptInvitation accepts a group invitation
func (db *DB) AcceptInvitation(invitationID, userID string) error {
	tx, err := db.conn.BeginTx(context.Background(), nil)
	if err != nil {
		return fmt.Errorf("failed to begin transaction: %w", err)
	}
	defer func() {
		if err := tx.Rollback(); err != nil && err != sql.ErrTxDone {
			log.Printf("ERROR: failed to rollback transaction: %v", err)
		}
	}()

	// Get invitation details
	var groupID string
	var query string
	if db.dbType == DBTypeSQLite {
		query = `SELECT group_id FROM group_invitations WHERE id = ? AND invited_user_id = ? AND status = 'pending'`
	} else {
		query = `SELECT group_id FROM group_invitations WHERE id = $1 AND invited_user_id = $2 AND status = 'pending'`
	}

	err = tx.QueryRowContext(context.Background(), query, invitationID, userID).Scan(&groupID)
	if err != nil {
		return fmt.Errorf("invitation not found or already processed: %w", err)
	}

	// Add user to group
	if db.dbType == DBTypeSQLite {
		query = `INSERT INTO group_members (group_id, user_id, role) VALUES (?, ?, 'member')`
	} else {
		query = `INSERT INTO group_members (group_id, user_id, role) VALUES ($1, $2, 'member')`
	}
	_, err = tx.ExecContext(context.Background(), query, groupID, userID)
	if err != nil {
		return fmt.Errorf("failed to add member: %w", err)
	}

	// Update invitation status
	if db.dbType == DBTypeSQLite {
		query = `UPDATE group_invitations SET status = 'accepted' WHERE id = ?`
	} else {
		query = `UPDATE group_invitations SET status = 'accepted' WHERE id = $1`
	}
	_, err = tx.ExecContext(context.Background(), query, invitationID)
	if err != nil {
		return fmt.Errorf("failed to update invitation: %w", err)
	}

	return tx.Commit()
}

// DeclineInvitation declines a group invitation
func (db *DB) DeclineInvitation(invitationID, userID string) error {
	var query string
	if db.dbType == DBTypeSQLite {
		query = `UPDATE group_invitations SET status = 'declined' WHERE id = ? AND invited_user_id = ?`
	} else {
		query = `UPDATE group_invitations SET status = 'declined' WHERE id = $1 AND invited_user_id = $2`
	}

	_, err := db.conn.ExecContext(context.Background(), query, invitationID, userID)
	if err != nil {
		return fmt.Errorf("failed to decline invitation: %w", err)
	}
	return nil
}

// RemoveGroupMember removes a member from a group
func (db *DB) RemoveGroupMember(groupID, userID string) error {
	var query string
	if db.dbType == DBTypeSQLite {
		query = `DELETE FROM group_members WHERE group_id = ? AND user_id = ?`
	} else {
		query = `DELETE FROM group_members WHERE group_id = $1 AND user_id = $2`
	}

	_, err := db.conn.ExecContext(context.Background(), query, groupID, userID)
	if err != nil {
		return fmt.Errorf("failed to remove member: %w", err)
	}
	return nil
}

// UserRoleInTaskGroups returns the highest role (admin > member > viewer) the user
// holds across all groups associated with the task. Returns empty string if no access.
func (db *DB) UserRoleInTaskGroups(userID, taskID string) string {
	var query string
	if db.dbType == DBTypeSQLite {
		query = `
			SELECT gm.role FROM group_members gm
			JOIN task_group_access tga ON tga.group_id = gm.group_id
			WHERE gm.user_id = ? AND tga.task_id = ?
			ORDER BY CASE gm.role
				WHEN 'admin' THEN 1
				WHEN 'member' THEN 2
				WHEN 'viewer' THEN 3
			END
			LIMIT 1`
	} else {
		query = `
			SELECT gm.role FROM group_members gm
			JOIN task_group_access tga ON tga.group_id = gm.group_id
			WHERE gm.user_id = $1 AND tga.task_id = $2
			ORDER BY CASE gm.role
				WHEN 'admin' THEN 1
				WHEN 'member' THEN 2
				WHEN 'viewer' THEN 3
			END
			LIMIT 1`
	}

	var role string
	err := db.conn.QueryRowContext(context.Background(), query, userID, taskID).Scan(&role)
	if err != nil {
		return ""
	}
	return role
}

// GetOrCreateDefaultLabGroup creates the auto-provisioned lab group if it doesn't exist.
// Returns the group ID. If no DEFAULT_LAB_GROUP env var is set, returns empty string.
func (db *DB) GetOrCreateDefaultLabGroup(createdBy string) (string, error) {
	groupName := os.Getenv("DEFAULT_LAB_GROUP")
	if groupName == "" {
		return "", nil
	}

	// Use transaction to prevent race conditions during concurrent startup
	tx, err := db.conn.BeginTx(context.Background(), &sql.TxOptions{Isolation: sql.LevelSerializable})
	if err != nil {
		return "", fmt.Errorf("failed to begin transaction: %w", err)
	}
	defer func() {
		if err := tx.Rollback(); err != nil && err != sql.ErrTxDone {
			log.Printf("ERROR: failed to rollback transaction: %v", err)
		}
	}()

	// Check if group exists
	var groupID string
	var query string
	if db.dbType == DBTypeSQLite {
		query = `SELECT id FROM groups WHERE name = ?`
	} else {
		query = `SELECT id FROM groups WHERE name = $1`
	}
	err = tx.QueryRowContext(context.Background(), query, groupName).Scan(&groupID)
	if err == nil {
		if commitErr := tx.Commit(); commitErr != nil {
			return "", fmt.Errorf("failed to commit transaction: %w", commitErr)
		}
		return groupID, nil
	}
	if err != sql.ErrNoRows {
		return "", fmt.Errorf("failed to check for default lab group: %w", err)
	}

	// Create the group within the transaction
	id := fmt.Sprintf("group_%d", time.Now().UnixNano())
	if db.dbType == DBTypeSQLite {
		query = `INSERT INTO groups (id, name, description, created_by) VALUES (?, ?, ?, ?)`
	} else {
		query = `INSERT INTO groups (id, name, description, created_by) VALUES ($1, $2, $3, $4)`
	}
	_, err = tx.ExecContext(context.Background(), query, id, groupName, "Auto-provisioned default lab group", createdBy)
	if err != nil {
		return "", fmt.Errorf("failed to create default lab group: %w", err)
	}

	// Add creator as admin within the transaction
	if db.dbType == DBTypeSQLite {
		query = `INSERT INTO group_members (group_id, user_id, role) VALUES (?, ?, 'admin')`
	} else {
		query = `INSERT INTO group_members (group_id, user_id, role) VALUES ($1, $2, 'admin')`
	}
	_, err = tx.ExecContext(context.Background(), query, id, createdBy)
	if err != nil {
		return "", fmt.Errorf("failed to add creator as admin: %w", err)
	}

	if err := tx.Commit(); err != nil {
		return "", fmt.Errorf("failed to commit transaction: %w", err)
	}

	return id, nil
}

// EnsureUserInGroup adds a user to a group if not already a member.
// Default role is 'member'. Returns nil if already a member.
func (db *DB) EnsureUserInGroup(groupID, userID string, role string) error {
	if role == "" {
		role = "member"
	}

	var query string
	if db.dbType == DBTypeSQLite {
		query = `INSERT OR IGNORE INTO group_members (group_id, user_id, role) VALUES (?, ?, ?)`
	} else {
		query = `INSERT INTO group_members (group_id, user_id, role) VALUES ($1, $2, $3)
			ON CONFLICT (group_id, user_id) DO NOTHING`
	}

	_, err := db.conn.ExecContext(context.Background(), query, groupID, userID, role)
	if err != nil {
		return fmt.Errorf("failed to add user to group: %w", err)
	}
	return nil
}

// EnsureAllUsersGroup creates the 'all-users' system group if it doesn't exist.
// This group is used for institution visibility.
func (db *DB) EnsureAllUsersGroup() (string, error) {
	const groupID = "all-users"
	const groupName = "all-users"

	var query string
	if db.dbType == DBTypeSQLite {
		query = `INSERT OR IGNORE INTO groups (id, name, description, created_by) VALUES (?, ?, ?, ?)`
	} else {
		query = `INSERT INTO groups (id, name, description, created_by) VALUES ($1, $2, $3, $4)
			ON CONFLICT (id) DO NOTHING`
	}

	_, err := db.conn.ExecContext(context.Background(), query, groupID, groupName,
		"System group: all authenticated users", "system")
	if err != nil {
		return "", fmt.Errorf("failed to ensure all-users group: %w", err)
	}
	return groupID, nil
}

// EnsureUserInAllUsersGroup adds a user to the 'all-users' system group.
func (db *DB) EnsureUserInAllUsersGroup(userID string) error {
	allUsersGroupID, err := db.EnsureAllUsersGroup()
	if err != nil {
		return err
	}
	return db.EnsureUserInGroup(allUsersGroupID, userID, "member")
}

// ProvisionUserOnFirstLogin adds a new user to the default groups:
// 1. The 'all-users' system group (for institution visibility)
// 2. The DEFAULT_LAB_GROUP if configured (for lab visibility)
// This should be called when a user first authenticates/logs in.
func (db *DB) ProvisionUserOnFirstLogin(userID string) error {
	// Add to all-users system group first
	if err := db.EnsureUserInAllUsersGroup(userID); err != nil {
		return fmt.Errorf("failed to add user to all-users group: %w", err)
	}

	// Add to default lab group if configured
	defaultGroupID, err := db.GetOrCreateDefaultLabGroup("system")
	if err != nil {
		return fmt.Errorf("failed to get/create default lab group: %w", err)
	}
	if defaultGroupID != "" {
		if err := db.EnsureUserInGroup(defaultGroupID, userID, "member"); err != nil {
			return fmt.Errorf("failed to add user to default lab group: %w", err)
		}
	}

	return nil
}

// DeprovisionUser removes a user from all groups when they are deactivated/deleted.
// This prevents deactivated users from retaining institution-visibility access.
func (db *DB) DeprovisionUser(userID string) error {
	var query string
	if db.dbType == DBTypeSQLite {
		query = `DELETE FROM group_members WHERE user_id = ?`
	} else {
		query = `DELETE FROM group_members WHERE user_id = $1`
	}

	_, err := db.conn.ExecContext(context.Background(), query, userID)
	if err != nil {
		return fmt.Errorf("failed to remove user from groups: %w", err)
	}
	return nil
}