use crate::domain::handler::{BackendHandler, ListUsersRequest, RequestFilter, User};
use anyhow::{bail, Result};
use ldap3_server::simple::*;

fn make_dn_pair<I>(mut iter: I) -> Result<(String, String)>
where
    I: Iterator<Item = String>,
{
    let pair = (
        iter.next()
            .ok_or_else(|| anyhow::Error::msg("Empty DN element"))?,
        iter.next()
            .ok_or_else(|| anyhow::Error::msg("Missing DN value"))?,
    );
    if let Some(e) = iter.next() {
        bail!(
            r#"Too many elements in distinguished name: "{:?}", "{:?}", "{:?}""#,
            pair.0,
            pair.1,
            e
        )
    }
    Ok(pair)
}

fn parse_distinguished_name(dn: &str) -> Result<Vec<(String, String)>> {
    dn.split(',')
        .map(|s| make_dn_pair(s.split('=').map(String::from)))
        .collect()
}

fn get_attribute(user: &User, attribute: &str) -> Result<Vec<String>> {
    match attribute {
        "objectClass" => Ok(vec![
            "inetOrgPerson".to_string(),
            "posixAccount".to_string(),
            "mailAccount".to_string(),
        ]),
        "uid" => Ok(vec![user.user_id.to_string()]),
        "mail" => Ok(vec![user.email.to_string()]),
        "givenName" => Ok(vec![user.first_name.to_string()]),
        "sn" => Ok(vec![user.last_name.to_string()]),
        "cn" => Ok(vec![user.display_name.to_string()]),
        _ => bail!("Unsupported attribute: {}", attribute),
    }
}

fn make_ldap_search_result_entry(
    user: User,
    base_dn_str: &str,
    attributes: &[String],
) -> Result<LdapSearchResultEntry> {
    Ok(LdapSearchResultEntry {
        dn: format!("cn={},{}", user.user_id, base_dn_str),
        attributes: attributes
            .iter()
            .map(|a| {
                Ok(LdapPartialAttribute {
                    atype: a.to_string(),
                    vals: get_attribute(&user, a)?,
                })
            })
            .collect::<Result<Vec<LdapPartialAttribute>>>()?,
    })
}

fn is_subtree(subtree: &[(String, String)], base_tree: &[(String, String)]) -> bool {
    if subtree.len() < base_tree.len() {
        return false;
    }
    let size_diff = subtree.len() - base_tree.len();
    for i in 0..base_tree.len() {
        if subtree[size_diff + i] != base_tree[i] {
            return false;
        }
    }
    true
}

fn map_field(field: &str) -> Result<String> {
    Ok(if field == "uid" {
        "user_id".to_string()
    } else if field == "mail" {
        "email".to_string()
    } else if field == "cn" {
        "display_name".to_string()
    } else if field == "givenName" {
        "first_name".to_string()
    } else if field == "sn" {
        "last_name".to_string()
    } else if field == "avatar" {
        "avatar".to_string()
    } else if field == "creationDate" {
        "creation_date".to_string()
    } else {
        bail!("Unknown field: {}", field);
    })
}

fn convert_filter(filter: &LdapFilter) -> Result<RequestFilter> {
    match filter {
        LdapFilter::And(filters) => Ok(RequestFilter::And(
            filters.iter().map(convert_filter).collect::<Result<_>>()?,
        )),
        LdapFilter::Or(filters) => Ok(RequestFilter::Or(
            filters.iter().map(convert_filter).collect::<Result<_>>()?,
        )),
        LdapFilter::Not(filter) => Ok(RequestFilter::Not(Box::new(convert_filter(&*filter)?))),
        LdapFilter::Equality(field, value) => {
            Ok(RequestFilter::Equality(map_field(field)?, value.clone()))
        }
        _ => bail!("Unsupported filter"),
    }
}

pub struct LdapHandler<Backend: BackendHandler> {
    dn: String,
    backend_handler: Backend,
    pub base_dn: Vec<(String, String)>,
    base_dn_str: String,
    ldap_user_dn: String,
}

impl<Backend: BackendHandler> LdapHandler<Backend> {
    pub fn new(backend_handler: Backend, ldap_base_dn: String, ldap_user_dn: String) -> Self {
        Self {
            dn: "Unauthenticated".to_string(),
            backend_handler,
            base_dn: parse_distinguished_name(&ldap_base_dn).unwrap_or_else(|_| {
                panic!(
                    "Invalid value for ldap_base_dn in configuration: {}",
                    ldap_base_dn
                )
            }),
            base_dn_str: ldap_base_dn,
            ldap_user_dn,
        }
    }

    pub async fn do_bind(&mut self, sbr: &SimpleBindRequest) -> LdapMsg {
        match self
            .backend_handler
            .bind(crate::domain::handler::BindRequest {
                name: sbr.dn.clone(),
                password: sbr.pw.clone(),
            })
            .await
        {
            Ok(()) => {
                self.dn = sbr.dn.clone();
                sbr.gen_success()
            }
            Err(_) => sbr.gen_invalid_cred(),
        }
    }

    pub async fn do_search(&mut self, lsr: &SearchRequest) -> Vec<LdapMsg> {
        if self.dn != self.ldap_user_dn {
            return vec![lsr.gen_error(
                LdapResultCode::InsufficentAccessRights,
                r#"Current user is not allowed to query LDAP"#.to_string(),
            )];
        }
        let dn_parts = match parse_distinguished_name(&lsr.base) {
            Ok(dn) => dn,
            Err(_) => {
                return vec![lsr.gen_error(
                    LdapResultCode::OperationsError,
                    format!(r#"Could not parse base DN: "{}""#, lsr.base),
                )]
            }
        };
        if !is_subtree(&dn_parts, &self.base_dn) {
            // Search path is not in our tree, just return an empty success.
            return vec![lsr.gen_success()];
        }
        let filters = match convert_filter(&lsr.filter) {
            Ok(f) => Some(f),
            Err(_) => {
                return vec![lsr.gen_error(
                    LdapResultCode::UnwillingToPerform,
                    "Unsupported filter".to_string(),
                )]
            }
        };
        let users = match self
            .backend_handler
            .list_users(ListUsersRequest { filters })
            .await
        {
            Ok(users) => users,
            Err(e) => {
                return vec![lsr.gen_error(
                    LdapResultCode::Other,
                    format!(r#"Error during search for "{}": {}"#, lsr.base, e),
                )]
            }
        };

        users
            .into_iter()
            .map(|u| make_ldap_search_result_entry(u, &self.base_dn_str, &lsr.attrs))
            .map(|entry| Ok(lsr.gen_result_entry(entry?)))
            // If the processing succeeds, add a success message at the end.
            .chain(std::iter::once(Ok(lsr.gen_success())))
            .collect::<Result<Vec<_>>>()
            .unwrap_or_else(|e| vec![lsr.gen_error(LdapResultCode::NoSuchAttribute, e.to_string())])
    }

    pub fn do_whoami(&mut self, wr: &WhoamiRequest) -> LdapMsg {
        if self.dn == "Unauthenticated" {
            wr.gen_operror("Unauthenticated")
        } else {
            wr.gen_success(format!("dn: {}", self.dn).as_str())
        }
    }

    pub async fn handle_ldap_message(&mut self, server_op: ServerOps) -> Option<Vec<LdapMsg>> {
        let result = match server_op {
            ServerOps::SimpleBind(sbr) => vec![self.do_bind(&sbr).await],
            ServerOps::Search(sr) => self.do_search(&sr).await,
            ServerOps::Unbind(_) => {
                // No need to notify on unbind (per rfc4511)
                return None;
            }
            ServerOps::Whoami(wr) => vec![self.do_whoami(&wr)],
        };
        Some(result)
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::domain::handler::MockTestBackendHandler;
    use chrono::NaiveDateTime;
    use mockall::predicate::eq;
    use tokio;

    async fn setup_bound_handler(
        mut mock: MockTestBackendHandler,
    ) -> LdapHandler<MockTestBackendHandler> {
        mock.expect_bind().return_once(|_| Ok(()));
        let mut ldap_handler =
            LdapHandler::new(mock, "dc=example,dc=com".to_string(), "test".to_string());
        let request = SimpleBindRequest {
            msgid: 1,
            dn: "test".to_string(),
            pw: "pass".to_string(),
        };
        ldap_handler.do_bind(&request).await;
        ldap_handler
    }

    #[tokio::test]
    async fn test_bind() {
        let mut mock = MockTestBackendHandler::new();
        mock.expect_bind()
            .with(eq(crate::domain::handler::BindRequest {
                name: "test".to_string(),
                password: "pass".to_string(),
            }))
            .times(1)
            .return_once(|_| Ok(()));
        let mut ldap_handler =
            LdapHandler::new(mock, "dc=example,dc=com".to_string(), "test".to_string());

        let request = WhoamiRequest { msgid: 1 };
        assert_eq!(
            ldap_handler.do_whoami(&request),
            request.gen_operror("Unauthenticated")
        );

        let request = SimpleBindRequest {
            msgid: 2,
            dn: "test".to_string(),
            pw: "pass".to_string(),
        };
        assert_eq!(ldap_handler.do_bind(&request).await, request.gen_success());

        let request = WhoamiRequest { msgid: 3 };
        assert_eq!(
            ldap_handler.do_whoami(&request),
            request.gen_success("dn: test")
        );
    }

    #[tokio::test]
    async fn test_bind_invalid_credentials() {
        let mut mock = MockTestBackendHandler::new();
        mock.expect_bind()
            .with(eq(crate::domain::handler::BindRequest {
                name: "test".to_string(),
                password: "pass".to_string(),
            }))
            .times(1)
            .return_once(|_| Ok(()));
        let mut ldap_handler =
            LdapHandler::new(mock, "dc=example,dc=com".to_string(), "admin".to_string());

        let request = WhoamiRequest { msgid: 1 };
        assert_eq!(
            ldap_handler.do_whoami(&request),
            request.gen_operror("Unauthenticated")
        );

        let request = SimpleBindRequest {
            msgid: 2,
            dn: "test".to_string(),
            pw: "pass".to_string(),
        };
        assert_eq!(ldap_handler.do_bind(&request).await, request.gen_success());

        let request = WhoamiRequest { msgid: 3 };
        assert_eq!(
            ldap_handler.do_whoami(&request),
            request.gen_success("dn: test")
        );

        let request = SearchRequest {
            msgid: 2,
            base: "ou=people,dc=example,dc=com".to_string(),
            scope: LdapSearchScope::Base,
            filter: LdapFilter::And(vec![]),
            attrs: vec![],
        };
        assert_eq!(
            ldap_handler.do_search(&request).await,
            vec![request.gen_error(
                LdapResultCode::InsufficentAccessRights,
                r#"Current user is not allowed to query LDAP"#.to_string()
            )]
        );
    }

    #[test]
    fn test_is_subtree() {
        let subtree1 = &[
            ("ou".to_string(), "people".to_string()),
            ("dc".to_string(), "example".to_string()),
            ("dc".to_string(), "com".to_string()),
        ];
        let root = &[
            ("dc".to_string(), "example".to_string()),
            ("dc".to_string(), "com".to_string()),
        ];
        assert!(is_subtree(subtree1, root));
        assert!(!is_subtree(&[], root));
    }

    #[test]
    fn test_parse_distinguished_name() {
        let parsed_dn = &[
            ("ou".to_string(), "people".to_string()),
            ("dc".to_string(), "example".to_string()),
            ("dc".to_string(), "com".to_string()),
        ];
        assert_eq!(
            parse_distinguished_name("ou=people,dc=example,dc=com").expect("parsing failed"),
            parsed_dn
        );
    }

    #[tokio::test]
    async fn test_search() {
        let mut mock = MockTestBackendHandler::new();
        mock.expect_list_users().times(1).return_once(|_| {
            Ok(vec![
                User {
                    user_id: "bob_1".to_string(),
                    email: "bob@bobmail.bob".to_string(),
                    display_name: "Bôb Böbberson".to_string(),
                    first_name: "Bôb".to_string(),
                    last_name: "Böbberson".to_string(),
                    creation_date: NaiveDateTime::from_timestamp(1_000_000, 0),
                },
                User {
                    user_id: "jim".to_string(),
                    email: "jim@cricket.jim".to_string(),
                    display_name: "Jimminy Cricket".to_string(),
                    first_name: "Jim".to_string(),
                    last_name: "Cricket".to_string(),
                    creation_date: NaiveDateTime::from_timestamp(1_500_000, 0),
                },
            ])
        });
        let mut ldap_handler = setup_bound_handler(mock).await;
        let request = SearchRequest {
            msgid: 2,
            base: "ou=people,dc=example,dc=com".to_string(),
            scope: LdapSearchScope::Base,
            filter: LdapFilter::And(vec![]),
            attrs: vec![
                "objectClass".to_string(),
                "uid".to_string(),
                "mail".to_string(),
                "givenName".to_string(),
                "sn".to_string(),
                "cn".to_string(),
            ],
        };
        assert_eq!(
            ldap_handler.do_search(&request).await,
            vec![
                request.gen_result_entry(LdapSearchResultEntry {
                    dn: "cn=bob_1,dc=example,dc=com".to_string(),
                    attributes: vec![
                        LdapPartialAttribute {
                            atype: "objectClass".to_string(),
                            vals: vec![
                                "inetOrgPerson".to_string(),
                                "posixAccount".to_string(),
                                "mailAccount".to_string()
                            ]
                        },
                        LdapPartialAttribute {
                            atype: "uid".to_string(),
                            vals: vec!["bob_1".to_string()]
                        },
                        LdapPartialAttribute {
                            atype: "mail".to_string(),
                            vals: vec!["bob@bobmail.bob".to_string()]
                        },
                        LdapPartialAttribute {
                            atype: "givenName".to_string(),
                            vals: vec!["Bôb".to_string()]
                        },
                        LdapPartialAttribute {
                            atype: "sn".to_string(),
                            vals: vec!["Böbberson".to_string()]
                        },
                        LdapPartialAttribute {
                            atype: "cn".to_string(),
                            vals: vec!["Bôb Böbberson".to_string()]
                        }
                    ],
                }),
                request.gen_result_entry(LdapSearchResultEntry {
                    dn: "cn=jim,dc=example,dc=com".to_string(),
                    attributes: vec![
                        LdapPartialAttribute {
                            atype: "objectClass".to_string(),
                            vals: vec![
                                "inetOrgPerson".to_string(),
                                "posixAccount".to_string(),
                                "mailAccount".to_string()
                            ]
                        },
                        LdapPartialAttribute {
                            atype: "uid".to_string(),
                            vals: vec!["jim".to_string()]
                        },
                        LdapPartialAttribute {
                            atype: "mail".to_string(),
                            vals: vec!["jim@cricket.jim".to_string()]
                        },
                        LdapPartialAttribute {
                            atype: "givenName".to_string(),
                            vals: vec!["Jim".to_string()]
                        },
                        LdapPartialAttribute {
                            atype: "sn".to_string(),
                            vals: vec!["Cricket".to_string()]
                        },
                        LdapPartialAttribute {
                            atype: "cn".to_string(),
                            vals: vec!["Jimminy Cricket".to_string()]
                        }
                    ],
                }),
                request.gen_success()
            ]
        );
    }

    #[tokio::test]
    async fn test_search_filters() {
        let mut mock = MockTestBackendHandler::new();
        mock.expect_list_users()
            .with(eq(ListUsersRequest {
                filters: Some(RequestFilter::And(vec![RequestFilter::Or(vec![
                    RequestFilter::Not(Box::new(RequestFilter::Equality(
                        "user_id".to_string(),
                        "bob".to_string(),
                    ))),
                ])])),
            }))
            .times(1)
            .return_once(|_| Ok(vec![]));
        let mut ldap_handler = setup_bound_handler(mock).await;
        let request = SearchRequest {
            msgid: 2,
            base: "ou=people,dc=example,dc=com".to_string(),
            scope: LdapSearchScope::Base,
            filter: LdapFilter::And(vec![LdapFilter::Or(vec![LdapFilter::Not(Box::new(
                LdapFilter::Equality("uid".to_string(), "bob".to_string()),
            ))])]),
            attrs: vec!["objectClass".to_string()],
        };
        assert_eq!(
            ldap_handler.do_search(&request).await,
            vec![request.gen_success()]
        );
    }

    #[tokio::test]
    async fn test_search_unsupported_filters() {
        let mut ldap_handler = setup_bound_handler(MockTestBackendHandler::new()).await;
        let request = SearchRequest {
            msgid: 2,
            base: "ou=people,dc=example,dc=com".to_string(),
            scope: LdapSearchScope::Base,
            filter: LdapFilter::Present("uid".to_string()),
            attrs: vec!["objectClass".to_string()],
        };
        assert_eq!(
            ldap_handler.do_search(&request).await,
            vec![request.gen_error(
                LdapResultCode::UnwillingToPerform,
                "Unsupported filter".to_string()
            )]
        );
    }
}