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

use indicatif::ProgressBar;
use log::{info, trace};
use serde::{Deserialize, Serialize};

use crate::{
    cli::Cli,
    file::{self, Chunk, FileTrait},
    output::new_progressbar,
    sharry::{AliasID, Client, ShareID, Uri},
};

#[derive(Serialize, Deserialize, Debug)]
pub struct CacheFile {
    #[serde(skip)]
    file_name: PathBuf,

    uri: Uri,
    alias_id: AliasID,
    share_id: ShareID,

    uploading: Option<file::Uploading>,
    files: VecDeque<file::Checked>,
}

impl CacheFile {
    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
    }

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

        let state: Self = {
            let file = fs::File::open(&file_name)?;
            let reader = io::BufReader::new(file);
            serde_json::from_reader(reader).map_err(io::Error::other)?
        };

        if args.should_hash() {
            fn check_hash<'a>(
                file: &'a impl FileTrait<'a>,
                bar: &ProgressBar,
            ) -> crate::Result<()> {
                bar.set_message(format!("checking {:?}", file.get_name()));
                file.check_hash(|bytes| bar.inc(bytes))
            }

            info!("checking files in {state:?}");

            // BOOKMARK assumption: total file size < 2 EiB
            let total_size = {
                let upl_size = if let Some(upl) = state.peek_uploading() {
                    upl.get_size()
                } else {
                    0
                };
                upl_size + state.queue().iter().map(|&f| f.get_size()).sum::<u64>()
            };

            let bar = new_progressbar();
            bar.set_length(total_size);
            bar.enable_steady_tick(Duration::from_millis(50));

            if let Some(upl) = state.peek_uploading() {
                check_hash(upl, &bar)?;
            }

            for chk in state.queue() {
                check_hash(chk, &bar)?;
            }

            bar.finish_with_message("finished checking files");
        }

        Ok(Self { file_name, ..state })
    }

    pub fn from_args(
        args: &Cli,
        new_share: impl FnOnce(&Cli) -> crate::Result<ShareID>,
    ) -> crate::Result<Self> {
        let mut files = args.files.clone();

        if args.should_hash() {
            info!("hashing files {files:?}");

            let bar = new_progressbar();
            // BOOKMARK assumption: total file size < 2 EiB
            bar.set_length(files.iter().map(FileTrait::get_size).sum());
            bar.enable_steady_tick(Duration::from_millis(50));

            for chk in &mut files {
                bar.set_message(format!("hashing {:?}", chk.get_name()));
                chk.hash(|bytes| bar.inc(bytes))?;
            }

            bar.finish_with_message("finished hashing files");
        }

        Ok(Self {
            file_name: Self::cache_file(args),
            uri: args.get_uri(),
            alias_id: args.alias.clone(),
            share_id: new_share(args)?,
            uploading: None,
            files: files.into(),
        })
    }

    pub fn queue(&self) -> Vec<&file::Checked> {
        self.files.iter().collect()
    }

    pub fn get_uploading(
        &mut self,
        client: &impl Client,
    ) -> crate::Result<Option<&mut file::Uploading>> {
        if self.uploading.is_some() {
            Ok(self.uploading.as_mut())
        } else if let Some(chk) = self.files.pop_front() {
            let upl = chk.start_upload(client, &self.uri, &self.alias_id, &self.share_id)?;
            self.uploading.replace(upl);

            Ok(self.uploading.as_mut())
        } else {
            Ok(None)
        }
    }

    pub fn expect_uploading(&mut self) -> &mut file::Uploading {
        self.uploading
            .as_mut()
            .expect("expect_uploading called while not uploading")
    }

    pub fn peek_uploading(&self) -> Option<&file::Uploading> {
        self.uploading.as_ref()
    }

    pub fn check_eof(&mut self) -> Option<PathBuf> {
        if let Some(upl) = self.uploading.take() {
            match upl.check_eof() {
                Ok(upl) => self.uploading = Some(upl),
                Err(p) => return Some(p),
            }
        }

        None
    }

    pub fn rewind_chunk(mut self) -> Option<Self> {
        self.uploading = Some(
            self.uploading
                .take()
                .expect("rewind_chunk called while not uploading")
                .rewind()?,
        );

        Some(self)
    }

    pub fn abort_upload(&mut self) {
        self.files.push_front(
            self.uploading
                .take()
                .expect("abort_upload called while not uploading")
                .abort(),
        );
    }

    pub fn share_notify(&self, client: &impl Client) -> crate::Result<()> {
        client.share_notify(&self.uri, &self.alias_id, &self.share_id)
    }

    pub fn file_patch(&self, client: &impl Client, chunk: &Chunk) -> crate::Result<()> {
        client.file_patch(&self.uri, &self.alias_id, &self.share_id, chunk)
    }

    pub fn save(&self) -> io::Result<()> {
        let cache_dir = self.file_name.parent().ok_or_else(|| {
            io::Error::other(format!("orphan file {:?}", self.file_name.display()))
        })?;
        fs::create_dir_all(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(())
    }

    fn remove(path: &Path) -> io::Result<()> {
        fs::remove_file(path)?;

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

    pub fn clear_any(args: &Cli) {
        let _ = Self::remove(&Self::cache_file(args));
    }

    pub fn discard(self) -> io::Result<()> {
        Self::remove(&self.file_name)
    }
}