use anyhow::{anyhow, Context};
use redis::{self, AsyncCommands};
use futures_util::StreamExt;
use kittybox::database::Storage;
use kittybox::database::FileStorage;
use std::collections::HashMap;

/// Convert from a Redis storage to a new storage new_storage.
async fn convert_from_redis<S: Storage>(from: String, new_storage: S) -> anyhow::Result<()> {
    let db = redis::Client::open(from).context("Failed to open the Redis connection")?;

    let mut conn = db.get_async_std_connection().await.context("Failed to connect to Redis")?;

    // Rebinding to convince the borrow checker we're not smuggling stuff outta scope
    let storage = &new_storage;
    
    conn.hscan::<_, String>("posts").await?.map(|it| async move {
        let json = serde_json::from_str(&it);
        (it, json)
    }).for_each_concurrent(8, |it| async move {
        let (orig, res): (String, serde_json::Result<serde_json::Value>) = it.await;
        match res {
            Ok(json) => {
                // XXX this assumes a trusted database that was created with Kittybox that checks for UID matching user token's prefix
                let user = &(url::Url::parse(json["properties"]["uid"][0].as_str().unwrap()).unwrap().origin().ascii_serialization().clone() + "/");
                if let Err(err) = storage.clone().put_post(&json, user).await {
                    eprintln!("Error saving post: {}", err);
                }
            },
            Err(err) => {
                eprintln!("Error: {} (rejected JSON follows below on stderr)", err);
                eprintln!("{}", orig);
            }
        }
    }).await;

    let mut stream: redis::AsyncIter<String> = conn.scan_match("settings_*").await?;
    while let Some(key) = stream.next_item().await {
        let mut conn = db.get_async_std_connection().await.context("Failed to connect to Redis")?;
        let user = key.strip_prefix("settings_").unwrap();
        match conn.hgetall::<&str, HashMap<String, String>>(&key).await.context(format!("Failed getting settings from key {}", key)) {
            Ok(settings) => {
                for (k, v) in settings.iter() {
                    if let Err(e) = storage.set_setting(k, &user, v).await.with_context(|| format!("Failed setting {} for {}", k, user)) {
                        eprintln!("{}", e);
                    }
                }
            },
            Err(e) => {
                eprintln!("{}", e);
            }
        }
    }
    
    return Ok(());
}

#[async_std::main]
async fn main() -> anyhow::Result<()> {
    let mut args = std::env::args();
    args.next(); // skip argv[0]
    let old_uri = args.next().ok_or_else(|| anyhow!("No import source is provided."))?;
    let new_uri = args.next().ok_or_else(|| anyhow!("No import destination is provided."))?;

    let storage = if new_uri.starts_with("file:") {
        let folder = new_uri.strip_prefix("file://").unwrap();
        let path = std::path::PathBuf::from(folder);
        Box::new(FileStorage::new(path).await.context("Failed to construct the file storage")?)
    } else {
        anyhow::bail!("Cannot construct the storage abstraction for destination storage. Check the storage type?");
    };
    
    if old_uri.starts_with("redis") {
        convert_from_redis(old_uri, *storage).await?
    }

    Ok(())
}