use std::collections::BTreeMap;

use anyhow::{Context as _, Result};

use super::{get_folder_meaning_by_attrs, get_folder_meaning_by_name};
use crate::config::Config;
use crate::imap::{session::Session, Imap};
use crate::log::LogExt;
use crate::tools::{self, time_elapsed};
use crate::{context::Context, imap::FolderMeaning};

impl Imap {
    /// Returns true if folders were scanned, false if scanning was postponed.
    pub(crate) async fn scan_folders(
        &mut self,
        context: &Context,
        session: &mut Session,
    ) -> Result<bool> {
        // First of all, debounce to once per minute:
        let mut last_scan = context.last_full_folder_scan.lock().await;
        if let Some(last_scan) = *last_scan {
            let elapsed_secs = time_elapsed(&last_scan).as_secs();
            let debounce_secs = context
                .get_config_u64(Config::ScanAllFoldersDebounceSecs)
                .await?;

            if elapsed_secs < debounce_secs {
                return Ok(false);
            }
        }
        info!(context, "Starting full folder scan");

        let folders = session.list_folders().await?;
        let watched_folders = get_watched_folders(context).await?;

        let mut folder_configs = BTreeMap::new();
        let mut folder_names = Vec::new();

        for folder in folders {
            let folder_meaning = get_folder_meaning_by_attrs(folder.attributes());
            if folder_meaning == FolderMeaning::Virtual {
                // Gmail has virtual folders that should be skipped. For example,
                // emails appear in the inbox and under "All Mail" as soon as it is
                // received. The code used to wrongly conclude that the email had
                // already been moved and left it in the inbox.
                continue;
            }
            folder_names.push(folder.name().to_string());
            let folder_name_meaning = get_folder_meaning_by_name(folder.name());

            if let Some(config) = folder_meaning.to_config() {
                // Always takes precedence
                folder_configs.insert(config, folder.name().to_string());
            } else if let Some(config) = folder_name_meaning.to_config() {
                // only set if none has been already set
                folder_configs
                    .entry(config)
                    .or_insert_with(|| folder.name().to_string());
            }

            let folder_meaning = match folder_meaning {
                FolderMeaning::Unknown => folder_name_meaning,
                _ => folder_meaning,
            };

            // Don't scan folders that are watched anyway
            if !watched_folders.contains(&folder.name().to_string())
                && folder_meaning != FolderMeaning::Drafts
                && folder_meaning != FolderMeaning::Trash
            {
                self.fetch_move_delete(context, session, folder.name(), folder_meaning)
                    .await
                    .context("Can't fetch new msgs in scanned folder")
                    .log_err(context)
                    .ok();
            }
        }

        // Set configs for necessary folders. Or reset if the folder was deleted.
        for conf in [
            Config::ConfiguredSentboxFolder,
            Config::ConfiguredTrashFolder,
        ] {
            let val = folder_configs.get(&conf).map(|s| s.as_str());
            let interrupt = conf == Config::ConfiguredTrashFolder
                && val.is_some()
                && context.get_config(conf).await?.is_none();
            context.set_config_internal(conf, val).await?;
            if interrupt {
                // `Imap::fetch_move_delete()` is possible now for other folders (NB: we are in the
                // Inbox loop).
                context.scheduler.interrupt_oboxes().await;
            }
        }

        info!(context, "Found folders: {folder_names:?}.");
        last_scan.replace(tools::Time::now());
        Ok(true)
    }
}

pub(crate) async fn get_watched_folder_configs(context: &Context) -> Result<Vec<Config>> {
    let mut res = vec![Config::ConfiguredInboxFolder];
    if context.get_config_bool(Config::SentboxWatch).await? {
        res.push(Config::ConfiguredSentboxFolder);
    }
    if context.should_watch_mvbox().await? {
        res.push(Config::ConfiguredMvboxFolder);
    }
    Ok(res)
}

pub(crate) async fn get_watched_folders(context: &Context) -> Result<Vec<String>> {
    let mut res = Vec::new();
    for folder_config in get_watched_folder_configs(context).await? {
        if let Some(folder) = context.get_config(folder_config).await? {
            res.push(folder);
        }
    }
    Ok(res)
}
