use std::sync::Arc;

use axum::extract::State;
use axum::http::{header, HeaderMap, StatusCode};
use axum::response::{IntoResponse, Response};
use axum::Json;
use chrono::{DateTime, Utc};
use noisebell_common::{validate_bearer, CacheStatusResponse, DoorStatus, WebhookPayload};
use tokio::sync::Mutex;
use tracing::{error, info};

use crate::db;
use crate::db::ApplyStateOutcome;
use crate::types::WebhookTarget;
use crate::webhook;

static OPEN_PNG: &[u8] = include_bytes!("../assets/open.png");
static CLOSED_PNG: &[u8] = include_bytes!("../assets/closed.png");
static OFFLINE_PNG: &[u8] = include_bytes!("../assets/offline.png");

pub struct AppState {
    pub db: Arc<Mutex<rusqlite::Connection>>,
    pub client: reqwest::Client,
    pub inbound_api_key: String,
    pub webhooks: Vec<WebhookTarget>,
    pub retry_attempts: u32,
    pub retry_base_delay_secs: u64,
    pub webhook_last_request: std::sync::atomic::AtomicU64,
    pub webhook_tokens: std::sync::atomic::AtomicU32,
}

fn unix_now() -> u64 {
    std::time::SystemTime::now().duration_since(std::time::UNIX_EPOCH).unwrap().as_secs()
}

fn format_full_timestamp(ts: u64) -> String {
    DateTime::from_timestamp(ts as i64, 0)
        .map(|dt: DateTime<Utc>| dt.format("%A, %B %-d, %Y at %-I:%M:%S %p UTC").to_string())
        .unwrap_or_else(|| format!("unix timestamp {ts}"))
}

fn format_duration(seconds: u64) -> String {
    let units = [(86_400, "day"), (3_600, "hour"), (60, "minute"), (1, "second")];

    let mut remaining = seconds;
    let mut parts = Vec::new();

    for (unit_seconds, name) in units {
        if remaining >= unit_seconds {
            let count = remaining / unit_seconds;
            remaining %= unit_seconds;
            let suffix = if count == 1 { "" } else { "s" };
            parts.push(format!("{count} {name}{suffix}"));
        }

        if parts.len() == 2 {
            break;
        }
    }

    if parts.is_empty() {
        "0 seconds".to_string()
    } else if parts.len() == 1 {
        parts.remove(0)
    } else {
        format!("{} and {}", parts[0], parts[1])
    }
}

fn status_summary(
    status: DoorStatus,
    since: Option<u64>,
    last_checked: Option<u64>,
    now: u64,
) -> String {
    let since_text = since
        .map(|ts| {
            format!(
                "We've been {} since {}, which was {} ago.",
                status,
                format_full_timestamp(ts),
                format_duration(now.saturating_sub(ts)),
            )
        })
        .unwrap_or_else(|| format!("We're currently {}, but the start time is unknown.", status));

    match last_checked {
        Some(ts) => format!(
            "{since_text} Last checked {}, which was {} ago.",
            format_full_timestamp(ts),
            format_duration(now.saturating_sub(ts)),
        ),
        None => format!("{since_text} Last checked time is unknown."),
    }
}

const WEBHOOK_RATE_LIMIT: u32 = 10;
const WEBHOOK_RATE_WINDOW_SECS: u64 = 60;

pub async fn post_webhook(
    State(state): State<Arc<AppState>>,
    headers: HeaderMap,
    Json(body): Json<WebhookPayload>,
) -> StatusCode {
    if !validate_bearer(&headers, &state.inbound_api_key) {
        return StatusCode::UNAUTHORIZED;
    }

    // Simple rate limiting: reset tokens every window, reject if exhausted.
    let now = unix_now();
    let last = state.webhook_last_request.load(std::sync::atomic::Ordering::Relaxed);
    if now.saturating_sub(last) >= WEBHOOK_RATE_WINDOW_SECS {
        state.webhook_tokens.store(WEBHOOK_RATE_LIMIT, std::sync::atomic::Ordering::Relaxed);
        state.webhook_last_request.store(now, std::sync::atomic::Ordering::Relaxed);
    }
    let remaining = state.webhook_tokens.fetch_update(
        std::sync::atomic::Ordering::Relaxed,
        std::sync::atomic::Ordering::Relaxed,
        |n| if n > 0 { Some(n - 1) } else { None },
    );
    if remaining.is_err() {
        return StatusCode::TOO_MANY_REQUESTS;
    }

    let now = unix_now();
    let db = state.db.clone();
    let status = body.status;
    let timestamp = body.timestamp;
    let result = tokio::task::spawn_blocking(move || {
        let conn = db.blocking_lock();
        db::apply_state(&conn, status, timestamp, now)
    })
    .await
    .expect("db task panicked");

    match result {
        Ok(ApplyStateOutcome::Applied) => {
            info!(
                status = %status,
                timestamp = body.timestamp,
                "state updated via webhook"
            );

            webhook::forward(
                &state.client,
                &state.webhooks,
                &WebhookPayload { status, timestamp: body.timestamp },
                state.retry_attempts,
                state.retry_base_delay_secs,
            )
            .await;
        }
        Ok(ApplyStateOutcome::Duplicate) => {
            info!(
                status = %status,
                timestamp = body.timestamp,
                "duplicate webhook ignored"
            );
        }
        Ok(ApplyStateOutcome::Stale) => {
            info!(
                status = %status,
                timestamp = body.timestamp,
                "stale webhook ignored"
            );
        }
        Err(e) => {
            error!(error = %e, "failed to update state from webhook");
            return StatusCode::INTERNAL_SERVER_ERROR;
        }
    }

    StatusCode::OK
}

pub async fn get_status(
    State(state): State<Arc<AppState>>,
) -> Result<Json<CacheStatusResponse>, StatusCode> {
    let db = state.db.clone();
    let mut status = tokio::task::spawn_blocking(move || {
        let conn = db.blocking_lock();
        db::get_status(&conn)
    })
    .await
    .expect("db task panicked")
    .map_err(|e| {
        error!(error = %e, "failed to get status");
        StatusCode::INTERNAL_SERVER_ERROR
    })?;

    status.human_readable =
        status_summary(status.status, status.since, status.last_checked, unix_now());

    Ok(Json(status))
}

pub async fn health() -> StatusCode {
    StatusCode::OK
}

pub async fn get_image_open() -> impl IntoResponse {
    (
        [(header::CONTENT_TYPE, "image/png"), (header::CACHE_CONTROL, "public, max-age=86400")],
        OPEN_PNG,
    )
}

pub async fn get_image_closed() -> impl IntoResponse {
    (
        [(header::CONTENT_TYPE, "image/png"), (header::CACHE_CONTROL, "public, max-age=86400")],
        CLOSED_PNG,
    )
}

pub async fn get_image_offline() -> impl IntoResponse {
    (
        [(header::CONTENT_TYPE, "image/png"), (header::CACHE_CONTROL, "public, max-age=86400")],
        OFFLINE_PNG,
    )
}

pub async fn get_image(State(state): State<Arc<AppState>>) -> Response {
    let db = state.db.clone();
    let status = match tokio::task::spawn_blocking(move || {
        let conn = db.blocking_lock();
        db::get_current_status(&conn)
    })
    .await
    .expect("db task panicked")
    {
        Ok(status) => status,
        Err(e) => {
            error!(error = %e, "failed to get current status for image");
            return StatusCode::INTERNAL_SERVER_ERROR.into_response();
        }
    };

    let image = match status {
        DoorStatus::Open => OPEN_PNG,
        DoorStatus::Closed => CLOSED_PNG,
        DoorStatus::Offline => OFFLINE_PNG,
    };
    ([(header::CONTENT_TYPE, "image/png"), (header::CACHE_CONTROL, "public, max-age=5")], image)
        .into_response()
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn format_duration_uses_two_units() {
        assert_eq!(format_duration(57), "57 seconds");
        assert_eq!(format_duration(125), "2 minutes and 5 seconds");
        assert_eq!(format_duration(3_723), "1 hour and 2 minutes");
    }

    #[test]
    fn status_summary_includes_since_and_last_checked() {
        let summary = status_summary(DoorStatus::Open, Some(1_000), Some(1_125), 1_180);

        assert!(summary.contains("We've been open since"));
        assert!(summary.contains("which was 3 minutes ago"));
        assert!(summary.contains("Last checked"));
        assert!(summary.contains("55 seconds ago"));
    }
}