use std::sync::Arc;

use axum::extract::State;
use axum::http::{HeaderMap, StatusCode};
use axum::Json;
use base64::Engine;
use serde::{Deserialize, Serialize};

use crate::email;
use crate::serve::AppState;

#[derive(Serialize)]
pub struct Question {
    id: i64,
    question: String,
    answer: String,
    created_at: String,
    answered_at: String,
}

pub async fn get_questions(
    State(state): State<Arc<AppState>>,
) -> Result<Json<Vec<Question>>, StatusCode> {
    let db = state
        .db
        .lock()
        .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;
    let mut stmt = db
        .prepare(
            "SELECT id, question, answer, created_at, answered_at \
             FROM questions WHERE answer IS NOT NULL \
             ORDER BY answered_at DESC",
        )
        .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;

    let questions = stmt
        .query_map([], |row| {
            Ok(Question {
                id: row.get(0)?,
                question: row.get(1)?,
                answer: row.get(2)?,
                created_at: row.get(3)?,
                answered_at: row.get(4)?,
            })
        })
        .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?
        .collect::<Result<Vec<_>, _>>()
        .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;

    Ok(Json(questions))
}

#[derive(Deserialize)]
pub struct SubmitQuestion {
    question: String,
}

pub async fn post_question(
    State(state): State<Arc<AppState>>,
    headers: HeaderMap,
    Json(body): Json<SubmitQuestion>,
) -> Result<StatusCode, (StatusCode, String)> {
    if body.question.is_empty() || body.question.len() > 200 {
        return Err((
            StatusCode::BAD_REQUEST,
            "Question must be 1-200 characters".to_string(),
        ));
    }

    let ip = headers
        .get("x-forwarded-for")
        .and_then(|v| v.to_str().ok())
        .and_then(|s| s.split(',').next())
        .map(|s| s.trim().to_string())
        .unwrap_or_else(|| "unknown".to_string());

    if !state.rate_limiter.check(&ip) {
        return Err((
            StatusCode::TOO_MANY_REQUESTS,
            "Too many questions. Try again later.".to_string(),
        ));
    }

    let id: i64 = {
        let db = state
            .db
            .lock()
            .map_err(|_| (StatusCode::INTERNAL_SERVER_ERROR, "db error".to_string()))?;
        db.execute(
            "INSERT INTO questions (question) VALUES (?1)",
            rusqlite::params![body.question],
        )
        .map_err(|_| {
            (
                StatusCode::INTERNAL_SERVER_ERROR,
                "insert error".to_string(),
            )
        })?;
        db.last_insert_rowid()
    };

    let notify_email = state.notify_email.clone();
    let mail_domain = state.mail_domain.clone();
    let qa_reply_domain = state.qa_reply_domain.clone();
    let question_text = body.question.clone();
    tokio::task::spawn_blocking(move || {
        if let Err(e) = email::send_notification(
            id,
            &question_text,
            &notify_email,
            &mail_domain,
            &qa_reply_domain,
        ) {
            eprintln!("Failed to send notification: {e}");
        }
    });

    Ok(StatusCode::CREATED)
}

// --- MTA Hook webhook types ---

#[derive(Deserialize)]
pub struct MtaHookPayload {
    #[serde(default)]
    pub messages: Vec<MtaHookMessage>,
    #[serde(default)]
    pub envelope: Envelope,
    #[serde(default)]
    pub message: MtaHookBody,
}

#[derive(Deserialize)]
pub struct MtaHookMessage {
    #[serde(default)]
    pub envelope: Envelope,
    #[serde(default)]
    pub message: MtaHookBody,
    #[serde(default)]
    pub contents: String,
}

#[derive(Deserialize, Default)]
pub struct Envelope {
    #[serde(default)]
    pub to: Vec<Recipient>,
}

#[derive(Deserialize)]
#[serde(untagged)]
pub enum Recipient {
    Address(String),
    WithAddress { address: String },
}

impl Default for Recipient {
    fn default() -> Self {
        Self::Address(String::new())
    }
}

impl Recipient {
    fn address(&self) -> &str {
        match self {
            Self::Address(address) => address,
            Self::WithAddress { address } => address,
        }
    }
}

#[derive(Deserialize, Default)]
pub struct MtaHookBody {
    #[serde(default)]
    pub subject: Option<String>,
    #[serde(default)]
    pub headers: MessageHeaders,
    #[serde(default)]
    pub contents: String,
}

#[derive(Deserialize, Default)]
pub struct MessageHeaders {
    #[serde(default)]
    pub subject: Option<String>,
}

#[derive(Serialize)]
pub struct MtaHookResponse {
    pub action: &'static str,
}

fn webhook_secret_matches(headers: &HeaderMap, expected_secret: &str) -> bool {
    let header_secret = headers
        .get("X-Webhook-Secret")
        .and_then(|v| v.to_str().ok())
        .unwrap_or("");
    if header_secret == expected_secret {
        return true;
    }

    let auth_header = match headers.get(axum::http::header::AUTHORIZATION) {
        Some(value) => value,
        None => return false,
    };
    let auth_header = match auth_header.to_str() {
        Ok(value) => value,
        Err(_) => return false,
    };
    let encoded = match auth_header.strip_prefix("Basic ") {
        Some(value) => value,
        None => return false,
    };
    let decoded = match base64::engine::general_purpose::STANDARD.decode(encoded) {
        Ok(value) => value,
        Err(_) => return false,
    };
    let credentials = match std::str::from_utf8(&decoded) {
        Ok(value) => value,
        Err(_) => return false,
    };
    let (_, password) = match credentials.split_once(':') {
        Some(parts) => parts,
        None => return false,
    };

    password == expected_secret
}

fn extract_qa_reply(payload: &MtaHookPayload, expected_domain: &str) -> Option<(i64, String)> {
    if !payload.messages.is_empty() {
        for message in &payload.messages {
            if let Some(reply) = extract_qa_reply_from_message(
                &message.envelope.to,
                expected_domain,
                message.message.subject.as_deref().or(message.message.headers.subject.as_deref()),
                if message.message.contents.is_empty() {
                    &message.contents
                } else {
                    &message.message.contents
                },
            ) {
                return Some(reply);
            }
        }
        return None;
    }

    extract_qa_reply_from_message(
        &payload.envelope.to,
        expected_domain,
        payload
            .message
            .subject
            .as_deref()
            .or(payload.message.headers.subject.as_deref()),
        &payload.message.contents,
    )
}

fn extract_qa_reply_from_message(
    recipients: &[Recipient],
    expected_domain: &str,
    subject: Option<&str>,
    contents: &str,
) -> Option<(i64, String)> {
    let _qa_recipient = recipients.iter().find(|recipient| {
        let address = recipient.address();
        let Some((local, domain)) = address.rsplit_once('@') else {
            return false;
        };

        local.eq_ignore_ascii_case("qa") && domain.eq_ignore_ascii_case(expected_domain)
    })?;

    let subject = subject.map(ToOwned::to_owned).or_else(|| {
        contents
            .replace("\r\n", "\n")
            .lines()
            .find_map(|line| line.strip_prefix("Subject: ").map(ToOwned::to_owned))
    })?;
    let id = email::extract_id_from_subject(&subject).ok()?;
    let body = email::extract_plain_text_body(contents);
    if body.is_empty() {
        return None;
    }

    Some((id, body))
}

pub async fn webhook(
    State(state): State<Arc<AppState>>,
    headers: HeaderMap,
    Json(payload): Json<MtaHookPayload>,
) -> Result<Json<MtaHookResponse>, (StatusCode, String)> {
    if !webhook_secret_matches(&headers, &state.webhook_secret) {
        eprintln!("Rejected webhook: invalid secret");
        return Err((StatusCode::UNAUTHORIZED, "invalid secret".to_string()));
    }

    if let Some((id, body)) = extract_qa_reply(&payload, &state.qa_reply_domain) {
        let db = state
            .db
            .lock()
            .map_err(|_| (StatusCode::INTERNAL_SERVER_ERROR, "db error".to_string()))?;
        db.execute(
            "UPDATE questions SET answer = ?1, answered_at = strftime('%Y-%m-%dT%H:%M:%SZ', 'now') \
             WHERE id = ?2 AND answer IS NULL",
            rusqlite::params![body, id],
        )
        .map_err(|_| (StatusCode::INTERNAL_SERVER_ERROR, "update error".to_string()))?;

        eprintln!("Stored Q&A reply for question #{id}");
        return Ok(Json(MtaHookResponse { action: "discard" }));
    }

    // No Q&A recipient matched — let Stalwart deliver normally
    Ok(Json(MtaHookResponse { action: "accept" }))
}

#[cfg(test)]
mod tests {
    use axum::http::HeaderMap;

    use super::{extract_qa_reply, webhook_secret_matches, MtaHookPayload};

    #[test]
    fn extracts_reply_from_current_stalwart_payload() {
        let payload: MtaHookPayload = serde_json::from_str(
            r#"{
                "envelope": {
                    "to": [
                        {
                            "address": "qa@extremist.software"
                        }
                    ]
                },
                "message": {
                    "subject": "Re: 42 - hello",
                    "contents": "This is the answer.\n\nOn earlier mail wrote:\n> quoted"
                }
            }"#,
        )
        .unwrap();

        assert_eq!(
            extract_qa_reply(&payload, "extremist.software"),
            Some((42, "This is the answer.".to_string()))
        );
    }

    #[test]
    fn extracts_reply_from_legacy_batch_payload() {
        let payload: MtaHookPayload = serde_json::from_str(
            r#"{
                "messages": [
                    {
                        "envelope": {
                            "to": ["qa@extremist.software"]
                        },
                        "message": {
                            "subject": "Re: 7 - legacy"
                        },
                        "contents": "Legacy answer"
                    }
                ]
            }"#,
        )
        .unwrap();

        assert_eq!(
            extract_qa_reply(&payload, "extremist.software"),
            Some((7, "Legacy answer".to_string()))
        );
    }

    #[test]
    fn accepts_header_secret() {
        let mut headers = HeaderMap::new();
        headers.insert("X-Webhook-Secret", "topsecret".parse().unwrap());

        assert!(webhook_secret_matches(&headers, "topsecret"));
    }

    #[test]
    fn accepts_basic_auth_password() {
        let mut headers = HeaderMap::new();
        headers.insert(
            axum::http::header::AUTHORIZATION,
            "Basic dXNlcjp0b3BzZWNyZXQ=".parse().unwrap(),
        );

        assert!(webhook_secret_matches(&headers, "topsecret"));
    }
}