use std::path::Path;

use entity::candidate;
use sea_orm::{prelude::Uuid, DbConn};
use tokio::io::{AsyncReadExt, AsyncWriteExt};

use crate::{
    candidate_details::EncryptedApplicationDetails,
    crypto::{self, hash_password},
    error::ServiceError,
    Mutation, Query,
};

use super::session_service::{AdminUser, SessionService};

const FIELD_OF_STUDY_PREFIXES: [&str; 3] = ["101", "102", "103"];

pub struct CandidateService;

impl CandidateService {
    /// Creates a new candidate with:
    /// Encrypted personal identification number
    /// Hashed password
    /// Encrypted private key
    /// Public key
    pub(in crate::services) async fn create(
        db: &DbConn,
        application_id: i32,
        plain_text_password: &String,
        personal_id_number: String,
    ) -> Result<candidate::Model, ServiceError> {
        // Check if application id starts with 101, 102 or 103
        if !CandidateService::is_application_id_valid(application_id) {
            return Err(ServiceError::InvalidApplicationId);
        }

        // Check if user with that application id already exists
        if Query::find_candidate_by_id(db, application_id)
            .await
            .unwrap()
            .is_some()
        {
            return Err(ServiceError::UserAlreadyExists);
        }

        let Ok(hashed_password) = hash_password(plain_text_password.to_string()).await else {
            return Err(ServiceError::CryptoHashFailed);
        };

        let (pubkey, priv_key_plain_text) = crypto::create_identity();

        let Ok(encrypted_priv_key) = crypto::encrypt_password(priv_key_plain_text, plain_text_password.to_string()).await else {
            return Err(ServiceError::CryptoEncryptFailed);
        };

        let Ok(hashed_personal_id_number) = hash_password(personal_id_number).await else {
            return Err(ServiceError::CryptoHashFailed);
        };

        // TODO: Specify root path in config?
        tokio::fs::create_dir_all(Path::new(&application_id.to_string()).join("cache")).await?;


        let candidate = Mutation::create_candidate(
            db,
            application_id,
            hashed_password,
            hashed_personal_id_number,
            pubkey,
            encrypted_priv_key,
        )
        .await?;
        Ok(candidate)
    }

    pub(in crate::services) async fn add_candidate_details(
        db: &DbConn,
        candidate: candidate::Model,
        enc_details: EncryptedApplicationDetails,
    ) -> Result<entity::candidate::Model, ServiceError> {
        let model = Mutation::add_candidate_details(db, candidate, enc_details.clone()).await?;
        Ok(model)
    }

    pub fn is_set_up(candidate: &candidate::Model) -> bool {
        candidate.name.is_some()
            && candidate.surname.is_some()
            && candidate.birthplace.is_some()
            && candidate.birthdate.is_some()
            && candidate.address.is_some()
            && candidate.telephone.is_some()
            && candidate.citizenship.is_some()
            && candidate.email.is_some()
            && candidate.sex.is_some()
            && candidate.study.is_some()
    }

    async fn write_portfolio_file(
        candidate_id: i32,
        data: Vec<u8>,
        filename: &str,
    ) -> Result<(), ServiceError> {
        let cache_path = Path::new(&candidate_id.to_string()).join("cache");

        let mut file = tokio::fs::File::create(cache_path.join(filename)).await?;

        file.write_all(&data).await?;

        Ok(())
    }

    pub async fn add_cover_letter(candidate_id: i32, letter: Vec<u8>) -> Result<(), ServiceError> {
        Self::write_portfolio_file(candidate_id, letter, "MOTIVACNI_DOPIS.pdf").await
    }

    pub async fn add_portfolio_letter(
        candidate_id: i32,
        letter: Vec<u8>,
    ) -> Result<(), ServiceError> {
        Self::write_portfolio_file(candidate_id, letter, "PORTFOLIO.pdf").await
    }

    pub async fn add_portfolio_zip(candidate_id: i32, zip: Vec<u8>) -> Result<(), ServiceError> {
        Self::write_portfolio_file(candidate_id, zip, "PORTFOLIO.zip").await
    }

    pub async fn is_portfolio_complete(candidate_id: i32) -> bool {
        let cache_path = Path::new(&candidate_id.to_string()).join("cache");

        tokio::fs::metadata(cache_path.join("MOTIVACNI_DOPIS.pdf"))
            .await
            .is_ok()
            && tokio::fs::metadata(cache_path.join("PORTFOLIO.pdf"))
                .await
                .is_ok()
            && tokio::fs::metadata(cache_path.join("PORTFOLIO.zip"))
                .await
                .is_ok()
    }

    pub async fn submit_portfolio(candidate_id: i32, db: &DbConn) -> Result<(), ServiceError> {
        let path = Path::new(&candidate_id.to_string()).to_path_buf();
        let cache_path = path.join("cache");

        if Self::is_portfolio_complete(candidate_id).await == false {
            return Err(ServiceError::IncompletePortfolio);
        }

        let mut archive = tokio::fs::File::create(path.join("PORTFOLIO.zip")).await?;

    
        let mut writer = async_zip::write::ZipFileWriter::new(&mut archive);

        for entry in vec!["MOTIVACNI_DOPIS.pdf", "PORTFOLIO.pdf", "PORTFOLIO.zip"] {
            let mut entry_file = tokio::fs::File::open(cache_path.join(entry))
                .await?;

            let mut contents = vec![];

            entry_file
                .read_to_end(&mut contents)
                .await?;

            let builder =
                async_zip::ZipEntryBuilder::new(entry.to_string(), async_zip::Compression::Deflate);

            let mut entry_writer = writer
                .write_entry_stream(builder)
                .await?;

            // TODO: write_all_buf?
            entry_writer
                .write_all(&mut contents)
                .await?;
        }

        // TODO: Ne unwrap
        writer.close().await.unwrap();
        archive.shutdown().await.unwrap();

        let admin_public_keys = Query::get_all_admin_public_keys(db)
            .await?;

        let candidate = Query::find_candidate_by_id(db, candidate_id)
            .await?;

        let Some(candidate) = candidate else {
            return Err(ServiceError::CandidateNotFound);
        };

        let candidate_public_key = candidate.public_key;

        let mut admin_public_keys_refrence: Vec<&str> =
            admin_public_keys.iter().map(|s| &**s).collect();

        let mut recipients = vec![&*candidate_public_key];

        recipients.append(&mut admin_public_keys_refrence);

        let Ok(_) = crypto::encrypt_file_with_recipients(
            path.join("PORTFOLIO.zip"),
            path.join("PORTFOLIO.zip"),
            recipients,
        )
        .await else {
            return Err(ServiceError::CryptoEncryptFailed);
        };

        Ok(())
    }

    pub async fn get_portfolio(candidate_id: i32, db: &DbConn) -> Result<Vec<u8>, ServiceError> {
        let candidate = Query::find_candidate_by_id(db, candidate_id)
            .await?;

        let Some(candidate) = candidate else {
            return Err(ServiceError::CandidateNotFound);
        };

        let candidate_public_key = candidate.public_key;

        let path = Path::new(&candidate_id.to_string()).join("PORTFOLIO.zip");

        let Ok(buffer) = crypto::decrypt_file_with_private_key_as_buffer(path, &candidate_public_key).await else {
            return Err(ServiceError::CryptoDecryptFailed);
        };

        Ok(buffer)
    }

    async fn decrypt_private_key(
        candidate: candidate::Model,
        password: String,
    ) -> Result<String, ServiceError> {
        let private_key_encrypted = candidate.private_key;

        let private_key = crypto::decrypt_password(private_key_encrypted, password).await;

        let Ok(private_key) = private_key else {
            return Err(ServiceError::CryptoDecryptFailed);
        };

        Ok(private_key)
    }

    pub async fn login(
        db: &DbConn,
        candidate_id: i32,
        password: String,
        ip_addr: String,
    ) -> Result<(String, String), ServiceError> {
        let candidate = Query::find_candidate_by_id(db, candidate_id)
            .await?
            .ok_or(ServiceError::CandidateNotFound)?;

        let session_id =
            SessionService::new_session(db, Some(candidate_id), None, password.clone(), ip_addr)
                .await;
        match session_id {
            Ok(session_id) => {
                let private_key = Self::decrypt_private_key(candidate, password).await?;
                Ok((session_id, private_key))
            }
            Err(e) => Err(e),
        }
    }

    pub async fn auth(db: &DbConn, session_uuid: Uuid) -> Result<candidate::Model, ServiceError> {
        match SessionService::auth_user_session(db, session_uuid).await {
            Ok(user) => match user {
                AdminUser::Candidate(candidate) => Ok(candidate),
                AdminUser::Admin(_) => unreachable!(),
            },
            Err(e) => Err(e),
        }
    }

    fn is_application_id_valid(application_id: i32) -> bool {
        let s = &application_id.to_string();
        if s.len() <= 3 {
            // TODO: does the field of study prefix have to be exactly 6 digits?
            return false;
        }
        let field_of_study_prefix = &s[0..3];
        FIELD_OF_STUDY_PREFIXES.contains(&field_of_study_prefix)
    }
}

#[cfg(test)]
mod tests {
    use sea_orm::{Database, DbConn};

    use crate::{crypto, services::candidate_service::CandidateService, Mutation};

    use super::EncryptedApplicationDetails;
    use chrono::NaiveDate;
    use entity::{candidate, parent};

    use crate::candidate_details::ApplicationDetails;
    use crate::services::application_service::ApplicationService;

    #[tokio::test]
    async fn test_application_id_validation() {
        assert!(CandidateService::is_application_id_valid(101_101));
        assert!(CandidateService::is_application_id_valid(102_107));
        assert!(CandidateService::is_application_id_valid(103_109));
        assert!(!CandidateService::is_application_id_valid(104_109));
        assert!(!CandidateService::is_application_id_valid(100_109));
        assert!(!CandidateService::is_application_id_valid(201_109));
        assert!(!CandidateService::is_application_id_valid(101));
    }

    #[cfg(test)]
    async fn get_memory_sqlite_connection() -> DbConn {
        use entity::{admin, candidate, parent};
        use sea_orm::Schema;
        use sea_orm::{sea_query::TableCreateStatement, ConnectionTrait, DbBackend};

        let base_url = "sqlite::memory:";
        let db: DbConn = Database::connect(base_url).await.unwrap();

        let schema = Schema::new(DbBackend::Sqlite);
        let stmt: TableCreateStatement = schema.create_table_from_entity(candidate::Entity);
        let stmt2: TableCreateStatement = schema.create_table_from_entity(admin::Entity);
        let stmt3: TableCreateStatement = schema.create_table_from_entity(parent::Entity);

        db.execute(db.get_database_backend().build(&stmt))
            .await
            .unwrap();
        db.execute(db.get_database_backend().build(&stmt2))
            .await
            .unwrap();
        db.execute(db.get_database_backend().build(&stmt3))
            .await
            .unwrap();
        db
    }

    #[tokio::test]
    async fn test_encrypt_decrypt_private_key_with_passphrase() {
        let db = get_memory_sqlite_connection().await;

        let plain_text_password = "test".to_string();

        let secret_message = "trnka".to_string();

        let candidate = CandidateService::create(&db, 103151, &plain_text_password, "".to_string())
            .await
            .ok()
            .unwrap();

        Mutation::create_parent(&db, 103151).await.unwrap();

        let encrypted_message =
            crypto::encrypt_password_with_recipients(&secret_message, &vec![&candidate.public_key])
                .await
                .unwrap();

        let private_key_plain_text =
            crypto::decrypt_password(candidate.private_key, plain_text_password)
                .await
                .unwrap();

        let decrypted_message =
            crypto::decrypt_password_with_private_key(&encrypted_message, &private_key_plain_text)
                .await
                .unwrap();

        assert_eq!(secret_message, decrypted_message);
    }

    #[cfg(test)]
    async fn put_user_data(db: &DbConn) -> (candidate::Model, parent::Model) {
        let plain_text_password = "test".to_string();
        let (candidate, parent) = ApplicationService::create_candidate_with_parent(
            &db,
            103151,
            &plain_text_password,
            "".to_string(),
        )
        .await
        .ok()
        .unwrap();

        let form = ApplicationDetails {
            name: "test".to_string(),
            surname: "aaa".to_string(),
            birthplace: "b".to_string(),
            birthdate: NaiveDate::from_ymd(1999, 1, 1),
            address: "test".to_string(),
            telephone: "test".to_string(),
            citizenship: "test".to_string(),
            email: "test".to_string(),
            sex: "test".to_string(),
            study: "test".to_string(),
            parent_name: "test".to_string(),
            parent_surname: "test".to_string(),
            parent_telephone: "test".to_string(),
            parent_email: "test".to_string(),
        };

        ApplicationService::add_all_details(&db, candidate.application, form)
            .await
            .unwrap()
    }

    #[tokio::test]
    async fn test_put_user_data() {
        let db = get_memory_sqlite_connection().await;
        let (candidate, parent) = put_user_data(&db).await;
        assert!(candidate.name.is_some());
        assert!(parent.name.is_some());
    }

    #[tokio::test]
    async fn test_encrypt_decrypt_user_data() {
        let password = "test".to_string();
        let db = get_memory_sqlite_connection().await;
        let (enc_candidate, enc_parent) = put_user_data(&db).await;

        let dec_priv_key = crypto::decrypt_password(enc_candidate.private_key.clone(), password)
            .await
            .unwrap();
        let enc_details = EncryptedApplicationDetails::try_from((enc_candidate, enc_parent))
            .ok()
            .unwrap();
        let dec_details = enc_details.decrypt(dec_priv_key).await.ok().unwrap();

        assert_eq!(dec_details.name, "test"); // TODO: test every element
        assert_eq!(dec_details.parent_surname, "test");
    }
}