package client

import (
	"crypto/tls"
	"crypto/x509"
	"fmt"
	"os"
	"sync"
	"time"

	"github.com/go-ldap/ldap/v3"
	"github.com/rs/zerolog"

	"github.com/gosec/gsc-ops-api/internal/config"
)

// LDAPClient manages a pool of LDAP connections
type LDAPClient struct {
	cfg    config.LDAPConfig
	pool   chan *ldap.Conn
	mu     sync.Mutex
	logger zerolog.Logger
}

// NewLDAPClient creates a new LDAP client with a connection pool
func NewLDAPClient(cfg config.LDAPConfig, logger zerolog.Logger) (*LDAPClient, error) {
	if len(cfg.Servers) == 0 {
		return nil, fmt.Errorf("no LDAP servers configured")
	}

	c := &LDAPClient{
		cfg:    cfg,
		pool:   make(chan *ldap.Conn, cfg.PoolSize),
		logger: logger.With().Str("component", "ldap").Logger(),
	}

	// Pre-fill pool with connections
	for i := 0; i < cfg.PoolSize; i++ {
		conn, err := c.connect()
		if err != nil {
			c.logger.Warn().Err(err).Int("index", i).Msg("failed to create initial LDAP connection")
			continue
		}
		c.pool <- conn
	}

	return c, nil
}

func (c *LDAPClient) connect() (*ldap.Conn, error) {
	var lastErr error
	for _, server := range c.cfg.Servers {
		var conn *ldap.Conn
		var err error

		if c.cfg.UseTLS {
			tlsCfg := &tls.Config{MinVersion: tls.VersionTLS12}
			if c.cfg.CAFile != "" {
				caCert, err := os.ReadFile(c.cfg.CAFile)
				if err != nil {
					lastErr = fmt.Errorf("failed to read CA file: %w", err)
					continue
				}
				pool := x509.NewCertPool()
				pool.AppendCertsFromPEM(caCert)
				tlsCfg.RootCAs = pool
			}
			conn, err = ldap.DialURL(server, ldap.DialWithTLSConfig(tlsCfg))
		} else {
			conn, err = ldap.DialURL(server)
		}

		if err != nil {
			lastErr = fmt.Errorf("failed to connect to %s: %w", server, err)
			continue
		}

		conn.SetTimeout(10 * time.Second)

		if err := conn.Bind(c.cfg.BindDN, c.cfg.BindPass); err != nil {
			conn.Close()
			lastErr = fmt.Errorf("failed to bind to %s: %w", server, err)
			continue
		}

		return conn, nil
	}
	return nil, fmt.Errorf("all LDAP servers failed: %w", lastErr)
}

// Acquire gets a connection from the pool, creating one if needed
func (c *LDAPClient) Acquire() (*ldap.Conn, error) {
	select {
	case conn := <-c.pool:
		// Test the connection with a no-op search
		_, err := conn.Search(&ldap.SearchRequest{
			BaseDN:   "",
			Scope:    ldap.ScopeBaseObject,
			Filter:   "(objectClass=*)",
			SizeLimit: 1,
		})
		if err != nil {
			conn.Close()
			return c.connect()
		}
		return conn, nil
	default:
		return c.connect()
	}
}

// Release returns a connection to the pool
func (c *LDAPClient) Release(conn *ldap.Conn) {
	if conn == nil {
		return
	}
	select {
	case c.pool <- conn:
	default:
		conn.Close()
	}
}

// Close closes all pooled connections
func (c *LDAPClient) Close() {
	close(c.pool)
	for conn := range c.pool {
		conn.Close()
	}
}

// Health checks LDAP connectivity
func (c *LDAPClient) Health() error {
	conn, err := c.Acquire()
	if err != nil {
		return err
	}
	defer c.Release(conn)
	return nil
}

// Search executes an LDAP search
func (c *LDAPClient) Search(baseDN, filter string, attrs []string, sizeLimit int) ([]*ldap.Entry, error) {
	conn, err := c.Acquire()
	if err != nil {
		return nil, fmt.Errorf("failed to acquire LDAP connection: %w", err)
	}
	defer c.Release(conn)

	sr, err := conn.Search(&ldap.SearchRequest{
		BaseDN:     baseDN,
		Scope:      ldap.ScopeWholeSubtree,
		Filter:     filter,
		Attributes: attrs,
		SizeLimit:  sizeLimit,
	})
	if err != nil {
		// FreeIPA returns SizeLimitExceeded with partial results
		if ldap.IsErrorWithCode(err, ldap.LDAPResultSizeLimitExceeded) && sr != nil {
			return sr.Entries, nil
		}
		return nil, fmt.Errorf("LDAP search failed: %w", err)
	}

	return sr.Entries, nil
}

// SearchOne executes an LDAP search expecting exactly one result
func (c *LDAPClient) SearchOne(baseDN, filter string, attrs []string) (*ldap.Entry, error) {
	entries, err := c.Search(baseDN, filter, attrs, 1)
	if err != nil {
		return nil, err
	}
	if len(entries) == 0 {
		return nil, nil
	}
	return entries[0], nil
}

// Add adds an LDAP entry
func (c *LDAPClient) Add(req *ldap.AddRequest) error {
	conn, err := c.Acquire()
	if err != nil {
		return fmt.Errorf("failed to acquire LDAP connection: %w", err)
	}
	defer c.Release(conn)

	return conn.Add(req)
}

// Modify modifies an LDAP entry
func (c *LDAPClient) Modify(req *ldap.ModifyRequest) error {
	conn, err := c.Acquire()
	if err != nil {
		return fmt.Errorf("failed to acquire LDAP connection: %w", err)
	}
	defer c.Release(conn)

	return conn.Modify(req)
}

// Delete deletes an LDAP entry
func (c *LDAPClient) Delete(dn string) error {
	conn, err := c.Acquire()
	if err != nil {
		return fmt.Errorf("failed to acquire LDAP connection: %w", err)
	}
	defer c.Release(conn)

	return conn.Del(&ldap.DelRequest{DN: dn})
}

// PasswordModify changes a user's password
func (c *LDAPClient) PasswordModify(userDN, newPassword string) error {
	conn, err := c.Acquire()
	if err != nil {
		return fmt.Errorf("failed to acquire LDAP connection: %w", err)
	}
	defer c.Release(conn)

	_, err = conn.PasswordModify(&ldap.PasswordModifyRequest{
		UserIdentity: userDN,
		NewPassword:  newPassword,
	})
	return err
}