use std::{
    collections::VecDeque,
    fs,
    io::{self, Write},
    path::{Path, PathBuf},
    time::Duration,
};

use console::style;
use indicatif::{ProgressBar, ProgressStyle};
use log::{debug, trace};
use serde::{Deserialize, Serialize};

use super::{
    cli::Cli,
    file::{self, FileTrait},
    sharry::{self, Client, ClientError, Uri},
};

#[derive(Serialize, Deserialize, Debug)]
pub struct AppState {
    #[serde(skip)]
    file_name: PathBuf,
    #[serde(skip)]
    progress: Option<ProgressBar>,
    #[serde(skip)]
    buffer: Vec<u8>,

    uri: Uri,
    alias_id: String,
    share_id: String,
    files: VecDeque<FileState>,
}

#[derive(Serialize, Deserialize, Debug)]
enum FileState {
    C(file::Checked),
    U(file::Uploading),
}

impl FileState {
    fn file_name(&self) -> &str {
        match self {
            FileState::C(checked) => checked.get_name(),
            FileState::U(uploading) => uploading.get_name(),
        }
    }

    fn start_upload(
        self,
        http: &impl Client,
        uri: &Uri,
        alias_id: &str,
        share_id: &str,
    ) -> sharry::Result<file::Uploading> {
        match self {
            FileState::C(checked) => {
                let endpoint = &uri.endpoint(format!("alias/upload/{share_id}/files/tus"));
                checked.start_upload(http, endpoint, alias_id)
            }
            FileState::U(uploading) => Ok(uploading),
        }
    }
}

impl AppState {
    fn cache_dir() -> PathBuf {
        let dir_name = dirs_next::cache_dir()
            .expect("could not determine cache directory")
            .join("shrupl");

        trace!("cachedir: {:?}", dir_name.display());
        dir_name
    }

    fn cache_file(args: &Cli) -> PathBuf {
        let file_name = Self::cache_dir().join(format!("{}.json", args.get_hash()));

        trace!("cachefile: {:?}", file_name.display());
        file_name
    }

    fn load(file_name: impl AsRef<Path>) -> io::Result<Self> {
        let content = fs::read_to_string(file_name)?;
        serde_json::from_str(&content).map_err(io::Error::other)
    }

    pub fn try_resume(args: &Cli) -> Option<Self> {
        let file_name = Self::cache_file(args);

        Self::load(&file_name)
            .inspect_err(|e| debug!("could not resume from {:?}: {e}", file_name.display()))
            .map(|state| {
                debug!("successfully loaded AppState");

                Self {
                    file_name,
                    progress: None,
                    buffer: Vec::with_capacity(args.chunk_size),
                    uri: state.uri,
                    alias_id: state.alias_id,
                    share_id: state.share_id,
                    files: state.files,
                }
            })
            .ok()
    }

    pub fn from_args(args: &Cli, http: &impl Client) -> sharry::Result<Self> {
        let file_name = Self::cache_file(args);

        let uri = args.get_uri();
        let alias_id = args.alias.clone();
        let share_id = http.share_create(
            &uri.endpoint("alias/upload/new"),
            &alias_id,
            args.get_share_request(),
        )?;

        let files: VecDeque<_> = args.files.clone().into_iter().map(FileState::C).collect();

        Ok(Self {
            file_name,
            progress: None,
            buffer: Vec::with_capacity(args.chunk_size),
            uri,
            alias_id,
            share_id,
            files,
        })
    }

    pub fn file_names(&self) -> Vec<&str> {
        self.files.iter().map(FileState::file_name).collect()
    }

    pub fn upload_chunk(&mut self, http: &impl Client) -> sharry::Result<Option<()>> {
        let mut uploading = if let Some(state) = self.files.pop_front() {
            state
                .start_upload(http, &self.uri, &self.alias_id, &self.share_id)
                .unwrap() // HACK unwrap
        } else {
            return Ok(None);
        };

        debug!("{uploading} chunk {}", self.buffer.len());

        // Initialize or fetch the existing ProgressBar in one call:
        let bar = &*self.progress.get_or_insert_with(|| {
            // Create a new bar with style
            let bar = ProgressBar::new(uploading.get_size())
                .with_style(
                    ProgressStyle::with_template(&format!(
                        concat!(
                            "{{msg:.yellow}}: {{bar:50.cyan/blue}} ",
                            "{{binary_bytes:.magenta}}{}{{binary_total_bytes:.magenta}} ",
                            "({{eta}})",
                        ),
                        style("/").magenta(),
                    ))
                    .unwrap(),
                )
                .with_message(uploading.get_name().to_owned())
                .with_position(uploading.get_offset());

            bar.enable_steady_tick(Duration::from_millis(100));
            bar
        });

        let chunk = uploading
            .read(&mut self.buffer)
            .map_err(ClientError::req_err)?;
        if chunk.get_length() == 0 {
            return Err(ClientError::req_err("wtf"));
        }

        http.file_patch(
            chunk.get_patch_uri(),
            &self.alias_id,
            chunk.get_offset(),
            chunk.get_data(),
        )?;

        match uploading.check_eof() {
            Ok(uploading) => {
                bar.set_position(uploading.get_offset());
                self.files.push_front(FileState::U(uploading));
                Ok(Some(()))
            }
            Err(path) => {
                debug!("Finished {:?}!", path.display());
                bar.finish();
                self.progress = None;

                let endpoint = self
                    .uri
                    .endpoint(format!("alias/mail/notify/{}", self.share_id));
                http.share_notify(&endpoint, &self.alias_id).unwrap(); // HACK unwrap

                Ok(self.files.front().map(drop))
            }
        }
    }

    pub fn save(&self) -> io::Result<()> {
        fs::create_dir_all(Self::cache_dir())?;

        let json = serde_json::to_string_pretty(self).map_err(io::Error::other)?;
        let mut file = fs::File::create(&self.file_name)?;
        file.write_all(json.as_bytes())?;

        trace!("updated {:?}", self.file_name.display());
        Ok(())
    }

    pub fn clear(self) -> io::Result<()> {
        fs::remove_file(&self.file_name)?;

        trace!("removed {:?}", self.file_name.display());
        Ok(())
    }
}