use crate::{
    backend::{Cancel, Options, Request, authorize},
    consent::Prompt,
};
use std::{
    collections::HashMap,
    io::Read,
    os::unix::{fs::PermissionsExt, net::UnixStream},
    path::{Path, PathBuf},
    process::Stdio,
    sync::{Arc, atomic::Ordering},
    time::Duration,
};
use tokio::{io::AsyncWriteExt, sync::Mutex};
use zbus::{
    Connection,
    message::Header,
    zvariant::{OwnedObjectPath, Value},
};

const PATH: &str = "/org/freedesktop/portal/desktop";
const MAX_IMAGE_BYTES: u64 = 128 * 1024 * 1024;
type Reply = (u32, Options);

#[derive(Clone, Default)]
pub(crate) struct Requests(Arc<Mutex<HashMap<String, (String, Arc<Cancel>)>>>);

impl Requests {
    pub(crate) async fn revoke_stale(&self, owner: Option<&str>) {
        for (request_owner, cancel) in self.0.lock().await.values() {
            if Some(request_owner.as_str()) != owner {
                cancel.stop();
            }
        }
    }

    pub(crate) async fn begin(
        &self,
        connection: &Connection,
        header: &Header<'_>,
        handle: &OwnedObjectPath,
    ) -> zbus::fdo::Result<Arc<Cancel>> {
        let owner = authorize(connection, header).await?;
        if !handle.as_str().starts_with(&format!("{PATH}/request/")) {
            return Err(zbus::fdo::Error::InvalidArgs("Invalid request path".into()));
        }
        let mut pending = self.0.lock().await;
        if pending.len() >= 8 || pending.contains_key(handle.as_str()) {
            return Err(zbus::fdo::Error::LimitsExceeded(
                "Request limit reached".into(),
            ));
        }
        let cancel = Arc::new(Cancel::default());
        if !connection
            .object_server()
            .at(
                handle,
                Request {
                    owner: owner.clone(),
                    cancel: cancel.clone(),
                },
            )
            .await?
        {
            return Err(zbus::fdo::Error::InvalidArgs(
                "Request already exists".into(),
            ));
        }
        pending.insert(handle.to_string(), (owner, cancel.clone()));
        Ok(cancel)
    }

    pub(crate) async fn end(&self, connection: &Connection, handle: &OwnedObjectPath) {
        self.0.lock().await.remove(handle.as_str());
        let _ = connection
            .object_server()
            .remove::<Request, _>(handle)
            .await;
    }
}

#[derive(Clone)]
pub(crate) struct Screenshot(pub(crate) Requests);

#[zbus::interface(name = "org.freedesktop.impl.portal.Screenshot")]
impl Screenshot {
    #[zbus(property, name = "version")]
    fn version(&self) -> u32 {
        3
    }

    #[zbus(property)]
    fn available_targets(&self) -> u32 {
        1 | 4
    }

    async fn screenshot(
        &self,
        handle: OwnedObjectPath,
        app_id: String,
        parent_window: String,
        options: Options,
        #[zbus(connection)] connection: &Connection,
        #[zbus(header)] header: Header<'_>,
    ) -> zbus::fdo::Result<(u32, Options)> {
        let cancel = self.0.begin(connection, &header, &handle).await?;
        let result = tokio::select! {
            biased;
            _ = cancel.wait() => (1, Options::new()),
            result = screenshot(&app_id, &parent_window, &options) => reply(result),
        };
        self.0.end(connection, &handle).await;
        Ok(result)
    }

    async fn pick_color(
        &self,
        handle: OwnedObjectPath,
        app_id: String,
        parent_window: String,
        _options: Options,
        #[zbus(connection)] connection: &Connection,
        #[zbus(header)] header: Header<'_>,
    ) -> zbus::fdo::Result<(u32, Options)> {
        let cancel = self.0.begin(connection, &header, &handle).await?;
        let result = tokio::select! {
            biased;
            _ = cancel.wait() => (1, Options::new()),
            result = pick_color(&app_id, &parent_window) => reply(result),
        };
        self.0.end(connection, &handle).await;
        Ok(result)
    }
}

#[derive(Clone)]
pub(crate) struct Wallpaper(pub(crate) Requests);

#[zbus::interface(name = "org.freedesktop.impl.portal.Wallpaper")]
impl Wallpaper {
    #[zbus(name = "SetWallpaperURI")]
    async fn set_wallpaper_uri(
        &self,
        handle: OwnedObjectPath,
        app_id: String,
        parent_window: String,
        uri: String,
        options: Options,
        #[zbus(connection)] connection: &Connection,
        #[zbus(header)] header: Header<'_>,
    ) -> zbus::fdo::Result<u32> {
        let cancel = self.0.begin(connection, &header, &handle).await?;
        let result = tokio::select! {
            biased;
            _ = cancel.wait() => 1,
            result = wallpaper(&app_id, &parent_window, &uri, &options, cancel.clone()) => reply(result).0,
        };
        self.0.end(connection, &handle).await;
        Ok(result)
    }
}

pub(crate) fn reply(result: Result<Option<Options>, String>) -> Reply {
    match result {
        Ok(Some(values)) => (0, values),
        Ok(None) => (1, Options::new()),
        Err(error) => {
            eprintln!("ferese portal: {error}");
            (2, Options::new())
        }
    }
}

pub(crate) async fn consent(
    app: &str,
    parent: &str,
    title: &str,
    description: &str,
    accept: &str,
    image: Option<PathBuf>,
) -> Result<bool, String> {
    if app.len() > 512 {
        return Err("Application ID is too long".into());
    }
    let prompt = Prompt {
        parent: parent.into(),
        title: title.into(),
        description: if app.is_empty() {
            description.into()
        } else {
            format!("{app}\n{description}")
        },
        accept: accept.into(),
        image,
        shortcuts: Vec::new(),
    };
    let mut child = crate::backend::child_command()?
        .arg("--consent")
        .stdin(Stdio::piped())
        .stdout(Stdio::piped())
        .stderr(Stdio::inherit())
        .kill_on_drop(true)
        .spawn()
        .map_err(|error| error.to_string())?;
    let pid = child.id().ok_or("Missing consent process ID")?;
    let mut input = child.stdin.take().unwrap();
    input
        .write_all(&serde_json::to_vec(&prompt).map_err(|error| error.to_string())?)
        .await
        .map_err(|error| error.to_string())?;
    drop(input);
    let output = tokio::time::timeout(Duration::from_secs(300), child.wait_with_output())
        .await
        .map_err(|_| "Consent timed out")?
        .map_err(|error| error.to_string())?;
    if output.status.success() && output.stdout == b"true\n" {
        wait_for_surface_removal(pid).await?;
        Ok(true)
    } else {
        Ok(false)
    }
}

pub(crate) async fn ipc(
    command: &'static str,
    args: serde_json::Value,
) -> Result<serde_json::Value, String> {
    tokio::task::spawn_blocking(move || {
        let path = std::env::var_os("XDG_RUNTIME_DIR")
            .map(PathBuf::from)
            .ok_or("Missing runtime directory")?
            .join("ferese/control.sock");
        let mut stream = UnixStream::connect(path).map_err(|error| error.to_string())?;
        stream
            .set_read_timeout(Some(Duration::from_secs(15)))
            .map_err(|error| error.to_string())?;
        stream
            .set_write_timeout(Some(Duration::from_secs(2)))
            .map_err(|error| error.to_string())?;
        let request = ferese_ipc::Request {
            version: ferese_ipc::VERSION,
            id: 1,
            kind: "command".into(),
            command: command.into(),
            args,
        };
        ferese_ipc::write_frame(&mut stream, &request).map_err(|error| error.to_string())?;
        let response: ferese_ipc::Response =
            ferese_ipc::read_frame(&mut stream).map_err(|error| error.to_string())?;
        if let Some(error) = response.error {
            return Err(error.message);
        }
        response.result.ok_or("Missing IPC result".into())
    })
    .await
    .map_err(|error| error.to_string())?
}

async fn select_geometry(point: bool, windows: Option<String>) -> Result<Option<String>, String> {
    let mut command = crate::backend::child_command_for("slurp")?;
    if point {
        command.arg("-p");
    }
    if windows.is_some() {
        command.arg("-r");
    }
    command.stdin(if windows.is_some() {
        Stdio::piped()
    } else {
        Stdio::null()
    });
    let mut child = command
        .stdout(Stdio::piped())
        .stderr(Stdio::inherit())
        .kill_on_drop(true)
        .spawn()
        .map_err(|error| error.to_string())?;
    let pid = child.id().ok_or("Missing selection process ID")?;
    if let Some(windows) = windows {
        let mut input = child.stdin.take().unwrap();
        input
            .write_all(windows.as_bytes())
            .await
            .map_err(|error| error.to_string())?;
        drop(input);
    }
    let output = tokio::time::timeout(Duration::from_secs(300), child.wait_with_output())
        .await
        .map_err(|_| "Selection timed out")?
        .map_err(|error| error.to_string())?;
    if !output.status.success() {
        return Ok(None);
    }
    let geometry = String::from_utf8(output.stdout)
        .map_err(|error| error.to_string())?
        .trim()
        .to_owned();
    if geometry.len() > 128 || geometry.is_empty() {
        return Err("Invalid selection".into());
    }
    wait_for_surface_removal(pid).await?;
    Ok(Some(geometry))
}

pub(crate) async fn wait_for_surface_removal(pid: u32) -> Result<(), String> {
    for _ in 0..100 {
        if ipc("has-client-surfaces", serde_json::json!({"pid": pid})).await? == false {
            return Ok(());
        }
        tokio::time::sleep(Duration::from_millis(10)).await;
    }
    Err("Screenshot helper is still visible".into())
}

async fn capture(geometry: Option<String>) -> Result<Vec<u8>, String> {
    let result = ipc("screenshot", serde_json::json!({"geometry": geometry})).await?;
    let path = result["path"]
        .as_str()
        .ok_or("Missing screenshot path")?
        .to_owned();
    tokio::task::spawn_blocking(move || {
        let file = std::fs::File::open(&path).map_err(|error| error.to_string())?;
        let _ = std::fs::remove_file(path);
        let mut bytes = Vec::new();
        file.take(MAX_IMAGE_BYTES + 1)
            .read_to_end(&mut bytes)
            .map_err(|error| error.to_string())?;
        if bytes.len() as u64 > MAX_IMAGE_BYTES {
            return Err("Screenshot is too large".into());
        }
        Ok(bytes)
    })
    .await
    .map_err(|error| error.to_string())?
}

async fn screenshot(app: &str, parent: &str, options: &Options) -> Result<Option<Options>, String> {
    let target = options
        .get("target")
        .map(u32::try_from)
        .transpose()
        .map_err(|_| "Invalid screenshot target")?
        .unwrap_or(
            if options
                .get("interactive")
                .map(bool::try_from)
                .transpose()
                .map_err(|_| "Invalid interactive hint")?
                .unwrap_or(false)
            {
                4
            } else {
                1
            },
        );
    if !matches!(target, 1 | 4) {
        return Err("Unsupported screenshot target".into());
    }
    if !consent(
        app,
        parent,
        "Take a screenshot?",
        "Allow this app to capture the selected screen content.",
        "Continue",
        None,
    )
    .await?
    {
        return Ok(None);
    }
    let geometry = match target {
        1 => None,
        4 => {
            let Some(geometry) = select_geometry(false, None).await? else {
                return Ok(None);
            };
            Some(geometry)
        }
        _ => unreachable!(),
    };
    let bytes = capture(geometry).await?;
    let directory = private_directory("screenshots")?;
    let mut file = tempfile::Builder::new()
        .prefix("screenshot-")
        .suffix(".png")
        .tempfile_in(directory)
        .map_err(|error| error.to_string())?;
    std::io::Write::write_all(&mut file, &bytes).map_err(|error| error.to_string())?;
    let (_, path) = file.keep().map_err(|error| error.to_string())?;
    Ok(Some(HashMap::from([(
        "uri".into(),
        Value::from(file_uri(&path)?)
            .try_to_owned()
            .map_err(|error| error.to_string())?,
    )])))
}

async fn pick_color(app: &str, parent: &str) -> Result<Option<Options>, String> {
    if !consent(
        app,
        parent,
        "Pick a screen color?",
        "Choose a pixel to share its color with this app.",
        "Choose color",
        None,
    )
    .await?
    {
        return Ok(None);
    }
    let Some(geometry) = select_geometry(true, None).await? else {
        return Ok(None);
    };
    let bytes = capture(Some(geometry)).await?;
    let color = png_color(&bytes)?;
    Ok(Some(HashMap::from([(
        "color".into(),
        Value::from(color)
            .try_to_owned()
            .map_err(|error| error.to_string())?,
    )])))
}

fn png_color(bytes: &[u8]) -> Result<(f64, f64, f64), String> {
    let mut decoder = png::Decoder::new(std::io::Cursor::new(bytes));
    decoder.set_transformations(png::Transformations::EXPAND | png::Transformations::STRIP_16);
    let mut reader = decoder.read_info().map_err(|error| error.to_string())?;
    let size = reader
        .output_buffer_size()
        .filter(|size| *size <= 16 * 1024)
        .ok_or("Unexpected pixel dimensions")?;
    let mut pixels = vec![0; size];
    let info = reader
        .next_frame(&mut pixels)
        .map_err(|error| error.to_string())?;
    if info.width == 0 || info.height == 0 {
        return Err("Empty image".into());
    }
    match info.color_type {
        png::ColorType::Rgb | png::ColorType::Rgba => Ok((
            pixels[0] as f64 / 255.,
            pixels[1] as f64 / 255.,
            pixels[2] as f64 / 255.,
        )),
        _ => Err("Unexpected screenshot pixel format".into()),
    }
}

fn private_directory(name: &str) -> Result<PathBuf, String> {
    let directory = dirs::data_local_dir()
        .ok_or("Missing data directory")?
        .join("ferese/portal")
        .join(name);
    std::fs::create_dir_all(&directory).map_err(|error| error.to_string())?;
    std::fs::set_permissions(&directory, std::fs::Permissions::from_mode(0o700))
        .map_err(|error| error.to_string())?;
    Ok(directory)
}

fn file_uri(path: &Path) -> Result<String, String> {
    url::Url::from_file_path(path)
        .map(String::from)
        .map_err(|_| "Invalid file path".into())
}

fn local_path(uri: &str) -> Result<PathBuf, String> {
    url::Url::parse(uri)
        .map_err(|error| error.to_string())?
        .to_file_path()
        .map_err(|_| "Wallpaper must be a local file URI".into())
}

async fn wallpaper(
    app: &str,
    parent: &str,
    uri: &str,
    options: &Options,
    cancel: Arc<Cancel>,
) -> Result<Option<Options>, String> {
    let target = options
        .get("set-on")
        .map(<&str>::try_from)
        .transpose()
        .map_err(|_| "Invalid wallpaper target")?
        .unwrap_or("background");
    if !matches!(target, "background" | "lockscreen" | "both") {
        return Err("Unsupported wallpaper target".into());
    }
    let input = local_path(uri)?;
    let preparing = cancel.clone();
    let file = tokio::task::spawn_blocking(move || prepare_wallpaper(&input, &preparing))
        .await
        .map_err(|error| error.to_string())??;
    if !consent(
        app,
        parent,
        "Change your wallpaper?",
        "Use this picture as your wallpaper.",
        "Set wallpaper",
        Some(file.path().to_path_buf()),
    )
    .await?
    {
        return Ok(None);
    }
    if cancel.stopped.load(Ordering::SeqCst) {
        return Ok(None);
    }
    let (_, path) = file.keep().map_err(|error| error.to_string())?;
    if let Err(error) = update_wallpaper(&path, target) {
        let _ = std::fs::remove_file(path);
        return Err(error);
    }
    Ok(Some(Options::new()))
}

fn prepare_wallpaper(input: &Path, cancel: &Cancel) -> Result<tempfile::NamedTempFile, String> {
    use std::os::unix::fs::OpenOptionsExt;
    let input = std::fs::OpenOptions::new()
        .read(true)
        .custom_flags(libc::O_NONBLOCK)
        .open(input)
        .map_err(|error| error.to_string())?;
    if !input
        .metadata()
        .map_err(|error| error.to_string())?
        .is_file()
    {
        return Err("Wallpaper must be a regular file".into());
    }
    let directory = private_directory("wallpapers")?;
    let mut file = tempfile::Builder::new()
        .prefix("wallpaper-")
        .tempfile_in(directory)
        .map_err(|error| error.to_string())?;
    let mut input = input.take(MAX_IMAGE_BYTES + 1);
    let mut size = 0u64;
    let mut buffer = [0; 64 * 1024];
    loop {
        if cancel.stopped.load(Ordering::SeqCst) {
            return Err("Wallpaper request cancelled".into());
        }
        let bytes = input.read(&mut buffer).map_err(|error| error.to_string())?;
        if bytes == 0 {
            break;
        }
        size += bytes as u64;
        if size > MAX_IMAGE_BYTES {
            return Err("Wallpaper is too large".into());
        }
        std::io::Write::write_all(&mut file, &buffer[..bytes])
            .map_err(|error| error.to_string())?;
    }
    if size == 0 {
        return Err("Wallpaper is empty".into());
    }
    let reader = image::ImageReader::open(file.path())
        .map_err(|error| error.to_string())?
        .with_guessed_format()
        .map_err(|error| error.to_string())?;
    let (width, height) = reader
        .into_dimensions()
        .map_err(|error| error.to_string())?;
    if width == 0
        || height == 0
        || width > 16384
        || height > 16384
        || u64::from(width) * u64::from(height) > MAX_IMAGE_BYTES / 4
    {
        return Err("Wallpaper dimensions exceed the image limit".into());
    }
    let mut reader = image::ImageReader::open(file.path())
        .map_err(|error| error.to_string())?
        .with_guessed_format()
        .map_err(|error| error.to_string())?;
    let mut limits = image::Limits::default();
    limits.max_alloc = Some(MAX_IMAGE_BYTES);
    reader.limits(limits);
    reader.decode().map_err(|error| error.to_string())?;
    Ok(file)
}

fn update_wallpaper(image: &Path, target: &str) -> Result<(), String> {
    let _transaction = crate::backend::CONFIG_TRANSACTION
        .lock()
        .map_err(|_| "Configuration transaction failed")?;
    let path = ferese_config::config_path().ok_or("Missing config path")?;
    edit_wallpaper(&path, image, target)
}

fn edit_wallpaper(path: &Path, image: &Path, target: &str) -> Result<(), String> {
    let source = match std::fs::read_to_string(&path) {
        Ok(source) => source,
        Err(error) if error.kind() == std::io::ErrorKind::NotFound => String::new(),
        Err(error) => return Err(error.to_string()),
    };
    let mut document =
        ferese_config::Document::parse(&source).map_err(|error| error.to_string())?;
    if target == "background" && document.get("theme.background.lock_path").is_none() {
        let old = document
            .get("theme.background.path")
            .and_then(serde_json::Value::as_str)
            .unwrap_or(ferese_config::default_wallpaper())
            .to_owned();
        document
            .set("theme.background.lock_path", old.into())
            .map_err(|error| error.to_string())?;
    }
    if target != "lockscreen" {
        document
            .set(
                "theme.background.path",
                image.to_string_lossy().into_owned().into(),
            )
            .map_err(|error| error.to_string())?;
    }
    if target != "background" {
        document
            .set(
                "theme.background.lock_path",
                image.to_string_lossy().into_owned().into(),
            )
            .map_err(|error| error.to_string())?;
    }
    let parent = path.parent().ok_or("Invalid config path")?;
    std::fs::create_dir_all(parent).map_err(|error| error.to_string())?;
    let mut temp = tempfile::NamedTempFile::new_in(parent).map_err(|error| error.to_string())?;
    std::io::Write::write_all(&mut temp, document.to_string().as_bytes())
        .map_err(|error| error.to_string())?;
    temp.as_file()
        .sync_all()
        .map_err(|error| error.to_string())?;
    if std::fs::read_to_string(&path).unwrap_or_default() != source {
        return Err("Configuration changed; please try again".into());
    }
    temp.persist(path).map_err(|error| error.to_string())?;
    Ok(())
}

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

    #[test]
    fn local_uris_preserve_special_characters_and_reject_network_paths() {
        let path = Path::new("/tmp/wallpaper #1_日本.png");
        assert_eq!(local_path(&file_uri(path).unwrap()).unwrap(), path);
        for uri in [
            "https://example.com/a.png",
            "file://example.com/a.png",
            "not a URI",
        ] {
            assert!(local_path(uri).is_err());
        }
    }

    #[test]
    fn pixel_color_is_normalized_rgb() {
        let mut bytes = Vec::new();
        let mut encoder = png::Encoder::new(&mut bytes, 1, 1);
        encoder.set_color(png::ColorType::Rgba);
        encoder.set_depth(png::BitDepth::Eight);
        encoder
            .write_header()
            .unwrap()
            .write_image_data(&[255, 128, 0, 255])
            .unwrap();
        assert_eq!(png_color(&bytes).unwrap(), (1., 128. / 255., 0.));
    }

    #[test]
    fn wallpaper_targets_preserve_independent_paths_and_other_settings() {
        let dir = tempfile::tempdir().unwrap();
        let path = dir.path().join("config.kdl");
        std::fs::write(&path, "// Keep my settings\ntheme { background { path \"/old.png\"; }; }; commands { terminal \"foot\"; }\n").unwrap();
        edit_wallpaper(&path, Path::new("/desktop.png"), "background").unwrap();
        let document =
            ferese_config::Document::parse(&std::fs::read_to_string(&path).unwrap()).unwrap();
        assert_eq!(
            document.get("theme.background.path").unwrap(),
            "/desktop.png"
        );
        assert_eq!(
            document.get("theme.background.lock_path").unwrap(),
            "/old.png"
        );
        assert!(
            std::fs::read_to_string(&path)
                .unwrap()
                .contains("Keep my settings")
        );
        edit_wallpaper(&path, Path::new("/lock.png"), "lockscreen").unwrap();
        let document =
            ferese_config::Document::parse(&std::fs::read_to_string(&path).unwrap()).unwrap();
        assert_eq!(
            document.get("theme.background.path").unwrap(),
            "/desktop.png"
        );
        assert_eq!(
            document.get("theme.background.lock_path").unwrap(),
            "/lock.png"
        );
        edit_wallpaper(&path, Path::new("/both.png"), "both").unwrap();
        let document =
            ferese_config::Document::parse(&std::fs::read_to_string(&path).unwrap()).unwrap();
        assert_eq!(document.get("theme.background.path").unwrap(), "/both.png");
        assert_eq!(
            document.get("theme.background.lock_path").unwrap(),
            "/both.png"
        );
        assert_eq!(
            document.get("commands.terminal").unwrap(),
            &serde_json::json!(["foot"])
        );
    }

    #[test]
    fn wallpaper_rejects_nonregular_files_and_cancellation_before_copy() {
        let dir = tempfile::tempdir().unwrap();
        assert!(prepare_wallpaper(dir.path(), &Cancel::default()).is_err());
        let path = dir.path().join("image");
        std::fs::write(&path, [0u8; 32]).unwrap();
        let cancel = Cancel::default();
        cancel.stop();
        assert!(
            prepare_wallpaper(&path, &cancel)
                .unwrap_err()
                .contains("cancelled")
        );
    }
}