use argon2::{Argon2, PasswordHasher, password_hash::SaltString};
use chrono::{Duration, Utc};
use serde::{Deserialize, Serialize};
use std::time::Duration as StdDuration;

use crate::error::AppError;
use crate::pb::email::{EmailAddress, SendEmailRequest};
use crate::service::AuthService;
use crate::session::Session;

#[derive(Debug, Clone, Deserialize, Serialize, utoipa::ToSchema)]
pub struct ResetPasswordRequest {
    pub email: String,
}

#[derive(Debug, Clone, Deserialize, Serialize, utoipa::ToSchema)]
pub struct ResetPasswordVerifyParams {
    pub token: String,
    pub password: String,
}

#[derive(Debug, Clone, Serialize, Deserialize, utoipa::ToSchema)]
struct PendingResetPassword {
    user_uid: uuid::Uuid,
    created_at: chrono::DateTime<Utc>,
}

impl AuthService {
    const RESET_PASS_PREFIX: &'static str = "auth:reset_pass:";
    const RESET_PASS_EXPIRY_HOURS: i64 = 1;
    const RESET_PASS_EXPIRY_SECS: u64 = 60 * 60;
    const RESET_PASS_COOLDOWN_SECS: u64 = 60; // 60 seconds between requests
    const RESET_PASS_DAILY_LIMIT: u64 = 5; // Max 5 requests per day
    const RESET_PASS_DAILY_SECS: u64 = 24 * 60 * 60; // 24 hours

    pub async fn auth_reset_password_request(
        &self,
        params: ResetPasswordRequest,
    ) -> Result<(), AppError> {
        let email = params.email.trim().to_lowercase();

        // Rate limiting: check cooldown
        let cooldown_key = format!("{}cooldown:{}", Self::RESET_PASS_PREFIX, email);
        if self.ctx.cache.exists(&cooldown_key) {
            tracing::warn!(email = %email, "Password reset request rate limited (cooldown)");
            return Ok(()); // Don't reveal if email exists
        }

        // Rate limiting: check daily limit
        let daily_key = format!("{}daily:{}", Self::RESET_PASS_PREFIX, email);
        let daily_count: u64 = self.ctx.cache.get(&daily_key).unwrap_or(0);
        if daily_count >= Self::RESET_PASS_DAILY_LIMIT {
            tracing::warn!(email = %email, count = daily_count, "Password reset request rate limited (daily limit)");
            return Ok(()); // Don't reveal if email exists
        }

        let user = self.auth_find_user_by_email(&email).await.ok();

        if let Some(user) = user {
            let token = super::generate_token("rst");
            let cache_key = format!("{}{}", Self::RESET_PASS_PREFIX, token);
            let now = chrono::Utc::now();

            if let Err(e) = self.ctx.cache.set(
                &cache_key,
                &PendingResetPassword {
                    user_uid: user.id,
                    created_at: now,
                },
                Some(StdDuration::from_secs(Self::RESET_PASS_EXPIRY_SECS)),
            ) {
                tracing::error!(error = %e, user_uid = %user.id, "Failed to cache reset token");
                return Ok(());
            }

            // Set cooldown
            if let Err(e) = self.ctx.cache.set(
                &cooldown_key,
                &true,
                Some(StdDuration::from_secs(Self::RESET_PASS_COOLDOWN_SECS)),
            ) {
                tracing::warn!(error = %e, "Failed to set cooldown");
            }

            // Increment daily counter
            let new_count = daily_count + 1;
            if let Err(e) = self.ctx.cache.set(
                &daily_key,
                &new_count,
                Some(StdDuration::from_secs(Self::RESET_PASS_DAILY_SECS)),
            ) {
                tracing::warn!(error = %e, "Failed to increment daily counter");
            }

            let domain = match self.ctx.config.main_domain() {
                Ok(d) => d,
                Err(e) => {
                    tracing::error!(error = %e, "Domain not configured for password reset");
                    return Ok(());
                }
            };
            let reset_link = format!("{}/auth/reset-password?token={}", domain, token);

            let mut mail = match self.ctx.registry.get_email_client() {
                Some(c) => c,
                None => {
                    tracing::error!("mail service not available");
                    return Ok(());
                }
            };
            if let Err(e) = mail
                .send_email(tonic::Request::new(SendEmailRequest {
                    to: vec![EmailAddress {
                        email: email.clone(),
                        name: String::new(),
                    }],
                    subject: "Reset Your Password".into(),
                    text_body: format!(
                        "You requested to reset your password.\n\n\
                         Reset your password here:\n\n{}\n\n\
                         If you did not request this, ignore this email.",
                        reset_link
                    ),
                    ..Default::default()
                }))
                .await
            {
                tracing::error!(error = %e, email = %email, "Failed to send password reset email");
            }

            tracing::info!(email = %email, user_uid = %user.id, "Password reset email sent");
        }

        Ok(())
    }

    pub async fn auth_reset_password_verify(
        &self,
        context: &Session,
        params: ResetPasswordVerifyParams,
    ) -> Result<(), AppError> {
        if params.token.is_empty() {
            return Err(AppError::InvalidResetToken);
        }

        let cache_key = format!("{}{}", Self::RESET_PASS_PREFIX, params.token);
        let pending = self
            .ctx
            .cache
            .get::<PendingResetPassword>(&cache_key)
            .ok_or(AppError::InvalidResetToken)?;

        if Utc::now() - pending.created_at > Duration::hours(Self::RESET_PASS_EXPIRY_HOURS) {
            let _ = self.ctx.cache.delete(&cache_key);
            return Err(AppError::ResetTokenExpired);
        }

        let password = self.auth_rsa_decode(context, params.password).await?;
        crate::service::util::validate_password_strength(&password)?;
        let _ = self.ctx.cache.delete(&cache_key);

        let salt = SaltString::generate(&mut rand::thread_rng());
        let password_hash = Argon2::default()
            .hash_password(password.as_bytes(), &salt)
            .map_err(|e| AppError::PasswordHashError(e.to_string()))?
            .to_string();

        let now = chrono::Utc::now();
        let result = sqlx::query(
            "UPDATE user_password SET password_hash = $1, password_updated_at = $2, updated_at = $2 \
             WHERE user_id = $3",
        )
        .bind(&password_hash)
        .bind(now)
        .bind(pending.user_uid)
        .execute(self.ctx.db.writer())
        .await
        .map_err(AppError::Database)?;

        if result.rows_affected() == 0 {
            return Err(AppError::InvalidResetToken);
        }

        tracing::info!(user_uid = %pending.user_uid, "Password reset successfully");
        Ok(())
    }
}