// TODO: validation for all dto

use std::sync::Arc;

use crate::{
    db::{
        DbServiceError,
        entities::{account::Column::Id, transaction::Model as TransactionModel},
    },
    services::transaction::{category::CategoryServiceError, tag::TagServiceError},
};

use crate::db::{
    Db,
    entities::transaction::{ActiveModel as TransactionActiveModel, Column::AccountId},
};
use sea_orm::{ActiveValue::Set, ColumnTrait, EntityTrait, QueryFilter};

use serde::{Deserialize, Serialize};
use thiserror::Error;

#[derive(Error, Debug)]
pub enum TransactionServiceError {
    #[error("database error: {0}")]
    DbErr(#[from] DbServiceError),
    #[error("Target not found: {0}")]
    TargetNotFound(String),
    #[error("Validation error: {0}")]
    Validation(String),
    #[error("unknown error: {0}")]
    Unknown(String),
}

impl From<sea_orm::DbErr> for TransactionServiceError {
    fn from(err: sea_orm::DbErr) -> Self {
        TransactionServiceError::DbErr(DbServiceError::from(err))
    }
}

impl From<TagServiceError> for TransactionServiceError {
    fn from(err: TagServiceError) -> Self {
        match err {
            TagServiceError::DbErr(db_err) => TransactionServiceError::DbErr(db_err),
            TagServiceError::TargetNotFound(msg) => TransactionServiceError::TargetNotFound(msg),
            TagServiceError::Validation(msg) => TransactionServiceError::Validation(msg),
            TagServiceError::Unknown(msg) => TransactionServiceError::Unknown(msg),
        }
    }
}

impl From<CategoryServiceError> for TransactionServiceError {
    fn from(err: CategoryServiceError) -> Self {
        match err {
            CategoryServiceError::DbErr(db_err) => TransactionServiceError::DbErr(db_err),
            CategoryServiceError::TargetNotFound(msg) => {
                TransactionServiceError::TargetNotFound(msg)
            }
            CategoryServiceError::Validation(msg) => TransactionServiceError::Validation(msg),
            CategoryServiceError::Unknown(msg) => TransactionServiceError::Unknown(msg),
        }
    }
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub enum TransactionType {
    #[serde(rename = "STANDARD")]
    Standard,
    #[serde(rename = "RECONCILIATION")]
    Reconciliation,
    #[serde(rename = "OPENING_BALANCE")]
    OpeningBalance,
    #[serde(other, rename = "UNKNOWN")]
    Unknown,
}

impl From<String> for TransactionType {
    fn from(s: String) -> Self {
        match serde_json::from_str::<TransactionType>(&format!("\"{}\"", s)) {
            Ok(t) => t,
            Err(_) => TransactionType::Unknown,
        }
    }
}

impl std::fmt::Display for TransactionType {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let s = match self {
            TransactionType::Standard => "STANDARD",
            TransactionType::Reconciliation => "RECONCILIATION",
            TransactionType::OpeningBalance => "OPENING_BALANCE",
            TransactionType::Unknown => "UNKNOWN",
        };
        write!(f, "{}", s)
    }
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Transaction {
    pub id: i64,
    pub account_id: i64,
    pub amount: String,
    pub transaction_type: TransactionType,
    pub currency_code: String,
    pub exchange_rate: Option<String>,
    pub transaction_date: String,
    pub metadata: TransactionMetadata,
    pub created_at: String,
    pub updated_at: String,
    pub from_account_id: Option<i64>,
    pub category_id: Option<i64>,
}

impl From<TransactionModel> for Transaction {
    fn from(model: TransactionModel) -> Self {
        Self {
            id: model.id,
            account_id: model.account_id,
            amount: model.amount,
            transaction_type: model.transaction_type.into(),
            currency_code: model.currency_code,
            exchange_rate: model.exchange_rate,
            transaction_date: model.transaction_date,
            metadata: TransactionMetadata::from(model.metadata),
            created_at: model.created_at.to_string(),
            updated_at: model.updated_at.to_string(),
            from_account_id: model.from_account_id,
            category_id: model.category_id,
        }
    }
}

#[derive(Default, Debug, Clone, Deserialize, Serialize)]
pub struct TransactionMetadata {}

impl From<String> for TransactionMetadata {
    fn from(s: String) -> Self {
        serde_json::from_str(&s).unwrap_or_default()
    }
}

impl From<Option<String>> for TransactionMetadata {
    fn from(s: Option<String>) -> Self {
        s.map(|s| serde_json::from_str(&s).unwrap_or_default())
            .unwrap_or_default()
    }
}

impl TransactionMetadata {
    pub fn validate(&self) -> Result<(), TransactionServiceError> {
        Ok(())
    }
}

async fn validate_account_exists<T>(
    account_id: i64,
    account_service: Arc<T>,
) -> Result<(), TransactionServiceError>
where
    T: crate::services::accounts::AccountsService + ?Sized,
{
    let account_exists = account_service
        .get_account(&account_id)
        .await
        // TODO: add error from account service to error chain
        .map_err(|err| TransactionServiceError::Unknown(err))?
        .is_some();
    if !account_exists {
        return Err(TransactionServiceError::Validation(format!(
            "Account with id {} does not exist",
            account_id
        )));
    }
    Ok(())
}

async fn validate_category_exists<T>(
    category_id: i64,
    category_service: Arc<T>,
) -> Result<(), TransactionServiceError>
where
    T: crate::services::CategoryService + ?Sized,
{
    let category_exists = category_service.get_category(category_id).await?.is_some();
    if !category_exists {
        return Err(TransactionServiceError::Validation(format!(
            "Category with id {} does not exist",
            category_id
        )));
    }
    Ok(())
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct CreateTransactionRequest {
    pub account_id: i64,
    pub amount: String,
    pub transaction_type: TransactionType,
    pub currency_code: String,
    pub exchange_rate: Option<String>,
    pub transaction_date: String,
    pub metadata: Option<TransactionMetadata>,
    pub from_account_id: Option<i64>,
    pub category_id: Option<i64>,
}

impl CreateTransactionRequest {
    pub async fn validate<T, U>(
        &self,
        account_service: Arc<T>,
        category_service: Arc<U>,
    ) -> Result<(), TransactionServiceError>
    where
        T: crate::services::accounts::AccountsService + ?Sized,
        U: crate::services::CategoryService + ?Sized,
    {
        if self.amount.trim().is_empty() {
            return Err(TransactionServiceError::Validation(
                "Amount cannot be empty".to_string(),
            ));
        }
        // check if amount is a valid decimal
        if self.amount.parse::<rust_decimal::Decimal>().is_err() {
            return Err(TransactionServiceError::Validation(
                "Amount must be a valid decimal".to_string(),
            ));
        }
        if self.currency_code.trim().is_empty() {
            return Err(TransactionServiceError::Validation(
                "Currency code cannot be empty".to_string(),
            ));
        }
        if self.transaction_date.trim().is_empty() {
            return Err(TransactionServiceError::Validation(
                "Transaction date cannot be empty".to_string(),
            ));
        }
        // check if transaction_date is a valid date
        if chrono::DateTime::parse_from_rfc3339(&self.transaction_date).is_err() {
            return Err(TransactionServiceError::Validation(
                "Transaction date must be a valid RFC3339 date".to_string(),
            ));
        }

        if let Some(metadata) = &self.metadata {
            metadata.validate()?;
        }

        validate_account_exists(self.account_id, account_service).await?;
        if let Some(category_id) = self.category_id {
            validate_category_exists(category_id, category_service).await?;
        }
        Ok(())
    }
}

impl From<CreateTransactionRequest> for TransactionActiveModel {
    fn from(request: CreateTransactionRequest) -> Self {
        Self {
            account_id: Set(request.account_id),
            amount: Set(request.amount),
            transaction_type: Set(request.transaction_type.to_string()),
            currency_code: Set(request.currency_code),
            exchange_rate: Set(request.exchange_rate),
            transaction_date: Set(request.transaction_date),
            metadata: Set(request
                .metadata
                .map(|m| serde_json::to_string(&m).unwrap_or_default())),
            from_account_id: Set(request.from_account_id),
            category_id: Set(request.category_id),
            created_at: Set(chrono::Utc::now().to_rfc3339()),
            updated_at: Set(chrono::Utc::now().to_rfc3339()),
            ..Default::default()
        }
    }
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct UpdateTransactionRequest {
    pub account_id: Option<i64>,
    pub amount: Option<String>,
    pub transaction_type: Option<TransactionType>,
    pub currency_code: Option<String>,
    pub exchange_rate: Option<Option<String>>,
    pub transaction_date: Option<String>,
    pub metadata: Option<Option<TransactionMetadata>>,
    pub from_account_id: Option<Option<i64>>,
    pub category_id: Option<Option<i64>>,
}

impl UpdateTransactionRequest {
    pub fn apply_to(self, transaction: &mut TransactionActiveModel) {
        if let Some(account_id) = self.account_id {
            transaction.account_id = Set(account_id);
        }
        if let Some(amount) = self.amount {
            transaction.amount = Set(amount);
        }
        if let Some(transaction_type) = self.transaction_type {
            transaction.transaction_type = Set(transaction_type.to_string());
        }
        if let Some(currency_code) = self.currency_code {
            transaction.currency_code = Set(currency_code);
        }
        if let Some(exchange_rate) = self.exchange_rate {
            transaction.exchange_rate = Set(exchange_rate);
        }
        if let Some(transaction_date) = self.transaction_date {
            transaction.transaction_date = Set(transaction_date);
        }
        if let Some(metadata) = self.metadata {
            transaction.metadata =
                Set(metadata.map(|m| serde_json::to_string(&m).unwrap_or_default()));
        }
        if let Some(from_account_id) = self.from_account_id {
            transaction.from_account_id = Set(from_account_id);
        }
        if let Some(category_id) = self.category_id {
            transaction.category_id = Set(category_id);
        }
    }

    pub async fn validate<T, U>(
        &self,
        account_service: Arc<T>,
        category_service: Arc<U>,
    ) -> Result<(), TransactionServiceError>
    where
        T: crate::services::accounts::AccountsService + ?Sized,
        U: crate::services::CategoryService + ?Sized,
    {
        if let Some(amount) = self.amount.as_ref()
            && amount.trim().is_empty()
        {
            return Err(TransactionServiceError::Validation(
                "Amount cannot be empty".to_string(),
            ));
        }
        // check if amount is a valid decimal
        if let Some(amount) = self.amount.as_ref()
            && amount.parse::<rust_decimal::Decimal>().is_err()
        {
            return Err(TransactionServiceError::Validation(
                "Amount must be a valid decimal".to_string(),
            ));
        }
        if let Some(currency_code) = self.currency_code.as_ref()
            && currency_code.trim().is_empty()
        {
            return Err(TransactionServiceError::Validation(
                "Currency code cannot be empty".to_string(),
            ));
        }
        if let Some(transaction_date) = self.transaction_date.as_ref()
            && transaction_date.trim().is_empty()
        {
            return Err(TransactionServiceError::Validation(
                "Transaction date cannot be empty".to_string(),
            ));
        }
        // check if transaction_date is a valid date
        if let Some(transaction_date) = self.transaction_date.as_ref()
            && chrono::DateTime::parse_from_rfc3339(transaction_date).is_err()
        {
            return Err(TransactionServiceError::Validation(
                "Transaction date must be a valid RFC3339 date".to_string(),
            ));
        }
        if let Some(Some(metadata)) = self.metadata.as_ref() {
            metadata.validate()?;
        }

        if let Some(account_id) = self.account_id {
            validate_account_exists(account_id, account_service).await?;
        }
        if let Some(Some(category_id)) = self.category_id {
            validate_category_exists(category_id, category_service).await?;
        }

        Ok(())
    }
}