use std::{
    collections::BTreeMap,
    mem::replace,
    ops::{Deref, DerefMut},
    sync::Arc,
};

use indexed_db_futures::{
    idb_object_store::IdbObjectStoreParameters,
    request::{IdbOpenDbRequestLike, OpenDbRequest},
    IdbDatabase, IdbKeyPath, IdbQuerySource, IdbVersionChangeEvent,
};
use itertools::Itertools;
use serde::{Deserialize, Serialize};
use wasm_bindgen::{JsCast, JsValue};
use wasm_bindgen_futures::{
    js_sys::{Array, Uint8Array},
    spawn_local,
};
use web_sys::{
    console, js_sys::Date, Blob, BlobPropertyBag, DomException, HtmlAnchorElement, IdbKeyRange,
    IdbTransactionMode, Url,
};

use crate::{echo_to_term_frame, GlobalMemoCell, TermFrame};

#[derive(Clone, Debug)]
pub enum QueuedAction {
    LogEvent(LogEvent),
    ReportOnLogStreams(TermFrame),
    DeleteLogs(DeleteLogs),
    DownloadLogs(DownloadLogs),
}

#[derive(Clone, Debug)]
pub struct DeleteLogs {
    pub reply_to: TermFrame,
    pub stream: String,
    pub min_date: String,
    pub max_date: String,
}

#[derive(Clone, Debug)]
pub struct DownloadLogs {
    pub reply_to: TermFrame,
    pub stream: String,
    pub min_date: String,
    pub max_date: String,
}

#[derive(Clone, Debug)]
pub struct LogEvent {
    pub log_stream: String,
    pub timestamp: Date,
    pub message: String,
}

#[derive(Serialize, Deserialize)]
pub struct StoredLogEvent {
    pub stream: String,
    pub timestamp: String,
    pub message: String,
}

impl From<&LogEvent> for StoredLogEvent {
    fn from(value: &LogEvent) -> Self {
        Self {
            stream: value.log_stream.clone(),
            timestamp: value
                .timestamp
                .to_iso_string()
                .as_string()
                .expect("timestamp to_iso_string wasn't string"),
            message: value.message.clone(),
        }
    }
}

pub enum LoggingEngine {
    Uninitialised,
    Initialising { backlog: Vec<QueuedAction> },
    Unavailable,
    Ready { db: Arc<IdbDatabase> },
}

impl Default for LoggingEngine {
    fn default() -> Self {
        Self::Uninitialised
    }
}

async fn async_init_logging() -> Result<LoggingEngine, DomException> {
    let mut db_req: OpenDbRequest = IdbDatabase::open_u32("logging", 1)?;
    db_req.set_on_upgrade_needed(Some(|evt: &IdbVersionChangeEvent| -> Result<(), JsValue> {
        if evt
            .db()
            .object_store_names()
            .find(|n| n == "logs")
            .is_none()
        {
            let store = evt.db().create_object_store_with_params(
                "logs",
                <IdbObjectStoreParameters as Default>::default().auto_increment(true),
            )?;
            store.create_index(
                "by_stream_timestamp",
                &IdbKeyPath::str_sequence(&["stream", "timestamp"]),
            )?;
        }
        Ok(())
    }));
    let db: IdbDatabase = db_req.await?;

    Ok(LoggingEngine::Ready { db: db.into() })
}

fn logging_broken_message(global: &GlobalMemoCell, frame: &TermFrame) {
    let _ = echo_to_term_frame(global, frame, "Couldn't enable logging. This sometimes happens if your browser doesn't enable indexed storage, or is in a mode (e.g. private browsing) where such storage is not permitted.\r\n");
}

fn init_logging(global: &GlobalMemoCell) {
    let global: GlobalMemoCell = global.clone();
    spawn_local(async move {
        match async_init_logging().await {
            Ok(new_engine) => {
                let old_engine = replace(global.log_engine.borrow_mut().deref_mut(), new_engine);
                if let LoggingEngine::Initialising { backlog } = old_engine {
                    for action in backlog.into_iter() {
                        match action {
                            QueuedAction::LogEvent(ev) => queue_immediate_log(&global, ev),
                            QueuedAction::ReportOnLogStreams(frame) => {
                                immediate_report_log_frame(&global, frame);
                            }
                            QueuedAction::DeleteLogs(act) => {
                                immediate_delete_logs(&global, act);
                            }
                            QueuedAction::DownloadLogs(act) => {
                                immediate_download_logs(&global, act);
                            }
                        }
                    }
                }
            }
            Err(_) => {
                if let LoggingEngine::Initialising { .. } = global.log_engine.borrow().deref() {
                    logging_broken_message(&global, &TermFrame(1));
                }
            }
        }
    })
}

fn queue_immediate_log_refutable(db: &IdbDatabase, event: &LogEvent) -> Result<(), String> {
    let trans = db
        .transaction_on_one_with_mode("logs", IdbTransactionMode::Readwrite)
        .map_err(|e| e.message())?;
    let store = trans.object_store("logs").map_err(|e| e.message())?;
    store
        .put_val(
            &serde_wasm_bindgen::to_value::<StoredLogEvent>(&event.into())
                .map_err(|_| "Can't serialise event")?,
        )
        .map_err(|e| e.message())?;
    Ok(())
}

fn queue_immediate_log(global: &GlobalMemoCell, event: LogEvent) {
    if let LoggingEngine::Ready { db } = global.log_engine.borrow().deref() {
        match queue_immediate_log_refutable(db, &event) {
            Ok(()) => {}
            Err(e) => {
                console::log_2(
                    &JsValue::from_str("Error writing event to IndexedDb"),
                    &JsValue::from(e),
                );
            }
        }
    }
}

async fn immediate_report_log_frame_refutable(
    global: GlobalMemoCell,
    db: &IdbDatabase,
    frame: TermFrame,
) -> Result<(), DomException> {
    let trans = db.transaction_on_one("logs")?;
    let store = trans.object_store("logs")?;
    let curs = store.open_cursor()?.await?;
    let curs = match curs {
        None => {
            let _ = echo_to_term_frame(&global, &frame, "No logs are currently stored.\r\n");
            return Ok(());
        }
        Some(curs) => curs,
    };
    let mut event_stats = BTreeMap::<String, u64>::new();
    loop {
        if let Ok(ev) = serde_wasm_bindgen::from_value::<StoredLogEvent>(curs.value()) {
            event_stats
                .entry(ev.stream)
                .and_modify(|v| *v += 1)
                .or_insert(1);
        };
        if !curs.continue_cursor()?.await? {
            break;
        }
    }
    let msg = event_stats
        .iter()
        .map(|(k, v)| format!("Log stream {} has {} log records.\r\n", k, v))
        .join("");
    let _ = echo_to_term_frame(&global, &frame, &msg);
    Ok(())
}

async fn immediate_report_log_frame_async(
    global: GlobalMemoCell,
    db: Arc<IdbDatabase>,
    frame: TermFrame,
) {
    match immediate_report_log_frame_refutable(global, &db, frame).await {
        Ok(()) => {}
        Err(e) => {
            console::log_2(
                &JsValue::from_str("Error reading log stats from IndexedDb"),
                &JsValue::from(e),
            );
        }
    }
}

fn immediate_report_log_frame(global: &GlobalMemoCell, frame: TermFrame) {
    let log_engine = global.log_engine.borrow();
    if let LoggingEngine::Ready { db } = log_engine.deref() {
        spawn_local(immediate_report_log_frame_async(
            global.clone(),
            db.clone(),
            frame,
        ));
    }
}

async fn immediate_delete_logs_refutable(
    global: GlobalMemoCell,
    db: &IdbDatabase,
    act: DeleteLogs,
) -> Result<(), DomException> {
    let trans = db.transaction_on_one_with_mode("logs", IdbTransactionMode::Readwrite)?;
    let store = trans.object_store("logs")?;
    let idx = store.index("by_stream_timestamp")?;
    let range = IdbKeyRange::bound(
        &JsValue::from(
            [
                JsValue::from_str(&act.stream),
                JsValue::from_str(&act.min_date),
            ]
            .iter()
            .collect::<Array>(),
        ),
        &JsValue::from(
            [
                JsValue::from_str(&act.stream),
                JsValue::from_str(&act.max_date),
            ]
            .iter()
            .collect::<Array>(),
        ),
    )?;
    let cur = match idx.open_key_cursor_with_range(&range)?.await? {
        None => {
            let _ = echo_to_term_frame(
                &global,
                &act.reply_to,
                "No logs matched; no logs deleted.\r\n",
            );
            return Ok(());
        }
        Some(cur) => cur,
    };
    let mut records: u64 = 0;
    loop {
        if let Some(pk) = cur.primary_key() {
            store.delete(&pk)?;
            records += 1;
        }
        if !cur.continue_cursor()?.await? {
            break;
        }
    }
    let _ = echo_to_term_frame(
        &global,
        &act.reply_to,
        &format!("{} logs matched and were deleted.\r\n", records),
    );
    Ok(())
}

async fn immediate_delete_logs_async(
    global: GlobalMemoCell,
    db: Arc<IdbDatabase>,
    act: DeleteLogs,
) {
    match immediate_delete_logs_refutable(global, &db, act).await {
        Ok(()) => {}
        Err(e) => {
            console::log_2(
                &JsValue::from_str("Error deleting logs from IndexedDb"),
                &JsValue::from(e),
            );
        }
    }
}

fn immediate_delete_logs(global: &GlobalMemoCell, act: DeleteLogs) {
    let log_engine = global.log_engine.borrow();
    if let LoggingEngine::Ready { db } = log_engine.deref() {
        spawn_local(immediate_delete_logs_async(
            global.clone(),
            db.clone(),
            act.clone(),
        ));
    }
}

async fn immediate_download_logs_refutable(
    global: GlobalMemoCell,
    db: &IdbDatabase,
    act: DownloadLogs,
) -> Result<(), DomException> {
    let trans = db.transaction_on_one_with_mode("logs", IdbTransactionMode::Readwrite)?;
    let store = trans.object_store("logs")?;
    let idx = store.index("by_stream_timestamp")?;
    let range = IdbKeyRange::bound(
        &JsValue::from(
            [
                JsValue::from_str(&act.stream),
                JsValue::from_str(&act.min_date),
            ]
            .iter()
            .collect::<Array>(),
        ),
        &JsValue::from(
            [
                JsValue::from_str(&act.stream),
                JsValue::from_str(&act.max_date),
            ]
            .iter()
            .collect::<Array>(),
        ),
    )?;
    let cur = match idx.open_key_cursor_with_range(&range)?.await? {
        None => {
            let _ = echo_to_term_frame(
                &global,
                &act.reply_to,
                "No logs matched; no logs downloaded.\r\n",
            );
            return Ok(());
        }
        Some(cur) => cur,
    };
    let mut buf: String = String::new();
    loop {
        if let Some(k) = cur.primary_key() {
            if let Some(Ok(rec)) = store
                .get(&k)?
                .await?
                .map(serde_wasm_bindgen::from_value::<StoredLogEvent>)
            {
                buf.push_str(&rec.message);
            }
        }
        if !cur.continue_cursor()?.await? {
            break;
        }
    }
    let buf_bytes = buf.as_bytes();
    let buf_array = Uint8Array::new_with_length(buf_bytes.len() as u32);
    buf_array.copy_from(buf_bytes);
    let mut blobprops: BlobPropertyBag = Default::default();
    blobprops.type_("text/plain");
    let blob = Blob::new_with_u8_array_sequence_and_options(
        &[&buf_array].into_iter().collect::<Array>(),
        &blobprops,
    )?;
    console::log_2(&buf_array, &blob);
    let url = Url::create_object_url_with_blob(&blob)?;
    if let Some((doc, body)) = web_sys::window()
        .and_then(|w| w.document())
        .and_then(|d| d.body().map(|b| (d, b)))
    {
        let el_anchor = JsCast::unchecked_into::<HtmlAnchorElement>(doc.create_element("a")?);
        body.append_child(&el_anchor)?;
        el_anchor.set_href(&url);
        el_anchor.set_download(&format!("{}-logs.txt", act.stream));
        el_anchor.click();
        body.remove_child(&el_anchor)?;
    }
    Url::revoke_object_url(&url)?;
    Ok(())
}

async fn immediate_download_logs_async(
    global: GlobalMemoCell,
    db: Arc<IdbDatabase>,
    act: DownloadLogs,
) {
    match immediate_download_logs_refutable(global, &db, act).await {
        Ok(()) => {}
        Err(e) => {
            console::log_2(
                &JsValue::from_str("Error downloading logs from IndexedDb"),
                &JsValue::from(e),
            );
        }
    }
}

fn immediate_download_logs(global: &GlobalMemoCell, act: DownloadLogs) {
    let log_engine = global.log_engine.borrow();
    if let LoggingEngine::Ready { db } = log_engine.deref() {
        spawn_local(immediate_download_logs_async(
            global.clone(),
            db.clone(),
            act.clone(),
        ));
    }
}

pub fn log(global: &GlobalMemoCell, event: &LogEvent) {
    let mut engine_borrow = global.log_engine.borrow_mut();
    match engine_borrow.deref_mut() {
        LoggingEngine::Uninitialised => {
            *engine_borrow = LoggingEngine::Initialising {
                backlog: vec![QueuedAction::LogEvent(event.clone())],
            };
            drop(engine_borrow);
            init_logging(global);
        }
        LoggingEngine::Initialising { ref mut backlog } => {
            backlog.push(QueuedAction::LogEvent(event.clone()));
        }
        LoggingEngine::Unavailable => {
            // Assume the user has already been informed it failed, so do nothing.
        }
        LoggingEngine::Ready { .. } => {
            drop(engine_borrow);
            queue_immediate_log(global, event.clone());
        }
    }
}

pub fn start_listing_logs(global: &GlobalMemoCell, send_to: &TermFrame) {
    let mut engine_borrow = global.log_engine.borrow_mut();
    match engine_borrow.deref_mut() {
        LoggingEngine::Uninitialised => {
            *engine_borrow = LoggingEngine::Initialising {
                backlog: vec![QueuedAction::ReportOnLogStreams(send_to.clone())],
            };
            drop(engine_borrow);
            init_logging(global);
        }
        LoggingEngine::Initialising { ref mut backlog } => {
            backlog.push(QueuedAction::ReportOnLogStreams(send_to.clone()));
        }
        LoggingEngine::Unavailable => {
            // Assume the user has already been informed it failed, so do nothing.
        }
        LoggingEngine::Ready { .. } => {
            drop(engine_borrow);
            immediate_report_log_frame(global, send_to.clone());
        }
    }
}

pub fn start_deleting_logs(
    global: &GlobalMemoCell,
    reply_to: &TermFrame,
    stream: &str,
    min_date: &str,
    max_date: &str,
) {
    let mut engine_borrow = global.log_engine.borrow_mut();
    let act = DeleteLogs {
        reply_to: reply_to.clone(),
        stream: stream.to_owned(),
        min_date: min_date.to_owned(),
        max_date: max_date.to_owned(),
    };
    match engine_borrow.deref_mut() {
        LoggingEngine::Uninitialised => {
            *engine_borrow = LoggingEngine::Initialising {
                backlog: vec![QueuedAction::DeleteLogs(act)],
            };
            drop(engine_borrow);
            init_logging(global);
        }
        LoggingEngine::Initialising { ref mut backlog } => {
            backlog.push(QueuedAction::DeleteLogs(act));
        }
        LoggingEngine::Unavailable => {
            // Assume the user has already been informed it failed, so do nothing.
        }
        LoggingEngine::Ready { .. } => {
            drop(engine_borrow);
            immediate_delete_logs(global, act);
        }
    }
}

pub fn start_downloading_logs(
    global: &GlobalMemoCell,
    reply_to: &TermFrame,
    stream: &str,
    min_date: &str,
    max_date: &str,
) {
    let mut engine_borrow = global.log_engine.borrow_mut();
    let act = DownloadLogs {
        reply_to: reply_to.clone(),
        stream: stream.to_owned(),
        min_date: min_date.to_owned(),
        max_date: max_date.to_owned(),
    };
    match engine_borrow.deref_mut() {
        LoggingEngine::Uninitialised => {
            *engine_borrow = LoggingEngine::Initialising {
                backlog: vec![QueuedAction::DownloadLogs(act)],
            };
            drop(engine_borrow);
            init_logging(global);
        }
        LoggingEngine::Initialising { ref mut backlog } => {
            backlog.push(QueuedAction::DownloadLogs(act));
        }
        LoggingEngine::Unavailable => {
            // Assume the user has already been informed it failed, so do nothing.
        }
        LoggingEngine::Ready { .. } => {
            drop(engine_borrow);
            immediate_download_logs(global, act);
        }
    }
}