package ldap

import (
	"crypto/rand"
	"encoding/base64"
	"fmt"
	"log"

	"git.nixc.us/a250/ss-atlas/internal/config"
	goldap "github.com/go-ldap/ldap/v3"
)

type Client struct {
	cfg *config.Config
}

type ProvisionResult struct {
	Username string
	Password string
	IsNew    bool
}

func New(cfg *config.Config) *Client {
	return &Client{cfg: cfg}
}

func (c *Client) connect() (*goldap.Conn, error) {
	conn, err := goldap.DialURL(c.cfg.LDAPUrl)
	if err != nil {
		return nil, fmt.Errorf("ldap dial: %w", err)
	}
	if err := conn.Bind(c.cfg.LDAPAdminDN, c.cfg.LDAPAdminPassword); err != nil {
		conn.Close()
		return nil, fmt.Errorf("ldap bind: %w", err)
	}
	return conn, nil
}

func (c *Client) ProvisionUser(username, email, stripeCustomerID string) (*ProvisionResult, error) {
	conn, err := c.connect()
	if err != nil {
		return nil, err
	}
	defer conn.Close()

	exists, err := c.userExists(conn, username)
	if err != nil {
		return nil, err
	}
	if exists {
		log.Printf("ldap user %s already exists", username)
		return &ProvisionResult{Username: username, IsNew: false}, nil
	}

	password := generatePassword()
	userDN := fmt.Sprintf("uid=%s,ou=people,%s", username, c.cfg.LDAPBaseDN)

	addReq := goldap.NewAddRequest(userDN, nil)
	addReq.Attribute("objectClass", []string{"inetOrgPerson"})
	addReq.Attribute("cn", []string{username})
	addReq.Attribute("sn", []string{username})
	addReq.Attribute("uid", []string{username})
	addReq.Attribute("mail", []string{email})
	addReq.Attribute("userPassword", []string{password})
	addReq.Attribute("description", []string{stripeCustomerID})

	if err := conn.Add(addReq); err != nil {
		return nil, fmt.Errorf("ldap add user %s: %w", username, err)
	}

	log.Printf("created ldap user %s (%s)", username, email)
	return &ProvisionResult{Username: username, Password: password, IsNew: true}, nil
}

func (c *Client) EnsureUser(username, email, stripeCustomerID string) error {
	_, err := c.ProvisionUser(username, email, stripeCustomerID)
	return err
}

func (c *Client) AddToGroup(username, groupName string) error {
	conn, err := c.connect()
	if err != nil {
		return err
	}
	defer conn.Close()

	groupDN := fmt.Sprintf("cn=%s,ou=groups,%s", groupName, c.cfg.LDAPBaseDN)
	userDN := fmt.Sprintf("uid=%s,ou=people,%s", username, c.cfg.LDAPBaseDN)

	modReq := goldap.NewModifyRequest(groupDN, nil)
	modReq.Add("member", []string{userDN})

	if err := conn.Modify(modReq); err != nil {
		return fmt.Errorf("ldap add %s to group %s: %w", username, groupName, err)
	}

	log.Printf("added %s to group %s", username, groupName)
	return nil
}

func (c *Client) RemoveFromGroup(username, groupName string) error {
	conn, err := c.connect()
	if err != nil {
		return err
	}
	defer conn.Close()

	groupDN := fmt.Sprintf("cn=%s,ou=groups,%s", groupName, c.cfg.LDAPBaseDN)
	userDN := fmt.Sprintf("uid=%s,ou=people,%s", username, c.cfg.LDAPBaseDN)

	modReq := goldap.NewModifyRequest(groupDN, nil)
	modReq.Delete("member", []string{userDN})

	if err := conn.Modify(modReq); err != nil {
		return fmt.Errorf("ldap remove %s from group %s: %w", username, groupName, err)
	}

	log.Printf("removed %s from group %s", username, groupName)
	return nil
}

func (c *Client) IsInGroup(username, groupName string) (bool, error) {
	conn, err := c.connect()
	if err != nil {
		return false, err
	}
	defer conn.Close()

	groupDN := fmt.Sprintf("cn=%s,ou=groups,%s", groupName, c.cfg.LDAPBaseDN)
	userDN := fmt.Sprintf("uid=%s,ou=people,%s", username, c.cfg.LDAPBaseDN)

	searchReq := goldap.NewSearchRequest(
		groupDN,
		goldap.ScopeBaseObject, goldap.NeverDerefAliases, 1, 0, false,
		fmt.Sprintf("(member=%s)", goldap.EscapeFilter(userDN)),
		[]string{"cn"},
		nil,
	)

	result, err := conn.Search(searchReq)
	if err != nil {
		return false, nil
	}

	return len(result.Entries) > 0, nil
}

func (c *Client) FindUserByDescription(stripeCustomerID string) (string, error) {
	conn, err := c.connect()
	if err != nil {
		return "", err
	}
	defer conn.Close()

	searchReq := goldap.NewSearchRequest(
		fmt.Sprintf("ou=people,%s", c.cfg.LDAPBaseDN),
		goldap.ScopeWholeSubtree, goldap.NeverDerefAliases, 1, 0, false,
		fmt.Sprintf("(description=%s)", goldap.EscapeFilter(stripeCustomerID)),
		[]string{"uid"},
		nil,
	)

	result, err := conn.Search(searchReq)
	if err != nil {
		return "", fmt.Errorf("ldap search by description: %w", err)
	}

	if len(result.Entries) == 0 {
		return "", fmt.Errorf("no user found with stripe customer %s", stripeCustomerID)
	}

	return result.Entries[0].GetAttributeValue("uid"), nil
}

func (c *Client) userExists(conn *goldap.Conn, username string) (bool, error) {
	searchReq := goldap.NewSearchRequest(
		fmt.Sprintf("ou=people,%s", c.cfg.LDAPBaseDN),
		goldap.ScopeWholeSubtree, goldap.NeverDerefAliases, 1, 0, false,
		fmt.Sprintf("(uid=%s)", goldap.EscapeFilter(username)),
		[]string{"uid"},
		nil,
	)

	result, err := conn.Search(searchReq)
	if err != nil {
		return false, fmt.Errorf("ldap search: %w", err)
	}

	return len(result.Entries) > 0, nil
}

func generatePassword() string {
	b := make([]byte, 18)
	if _, err := rand.Read(b); err != nil {
		panic("crypto/rand failed: " + err.Error())
	}
	return base64.URLEncoding.EncodeToString(b)
}