use std::convert::TryFrom;
use std::sync::{Arc, Mutex};

use anyhow::{anyhow, Result};
use lru::LruCache;
use tracing::trace;
use uuid::Uuid;

use crate::addressing::{Address, Addressable};
use crate::database::constants::{
    HIER_ADDR, HIER_HAS_ATTR, HIER_INVARIANT, IS_OF_TYPE_ATTR, LABEL_ATTR, TYPE_ADDR, TYPE_HAS_ATTR,
};
use crate::database::entry::{Entry, EntryValue};
use crate::database::lang::{PatternQuery, Query, QueryComponent, QueryPart};

use super::UpEndConnection;

#[derive(Debug, Clone, Eq, PartialEq, Hash)]
pub struct UNode(String);

impl UNode {
    pub fn new<T: Into<String>>(s: T) -> Result<Self> {
        let s = s.into();

        if s.is_empty() {
            return Err(anyhow!("UNode can not be empty."));
        }

        Ok(Self(s))
    }

    pub fn as_ref(&self) -> &String {
        &self.0
    }
}

#[derive(Debug, Clone, PartialEq)]
pub struct UHierPath(pub Vec<UNode>);

impl std::str::FromStr for UHierPath {
    type Err = anyhow::Error;

    fn from_str(string: &str) -> Result<Self, Self::Err> {
        if string.is_empty() {
            Ok(UHierPath(vec![]))
        } else {
            let result: Result<Vec<UNode>> = string
                .trim_end_matches('/')
                .split('/')
                .map(|part| UNode::new(String::from(part)))
                .collect();

            Ok(UHierPath(result?))
        }
    }
}

impl std::fmt::Display for UNode {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.0)
    }
}

impl std::fmt::Display for UHierPath {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(
            f,
            "{}",
            self.0
                .iter()
                .map(|node| node.to_string())
                .collect::<Vec<String>>()
                .join("/")
        )
    }
}

trait PointerEntries {
    fn extract_pointers(&self) -> Vec<(Address, Address)>;
}

impl PointerEntries for Vec<Entry> {
    fn extract_pointers(&self) -> Vec<(Address, Address)> {
        self.iter()
            .filter_map(|e| {
                if let EntryValue::Address(address) = &e.value {
                    Some((e.address().unwrap(), address.clone()))
                } else {
                    None
                }
            })
            .collect()
    }
}

pub fn list_roots(connection: &UpEndConnection) -> Result<Vec<Address>> {
    let all_directories: Vec<Entry> =
        connection.query(Query::SingleQuery(QueryPart::Matches(PatternQuery {
            entity: QueryComponent::Variable(None),
            attribute: QueryComponent::Exact(IS_OF_TYPE_ATTR.into()),
            value: QueryComponent::Exact(HIER_ADDR.clone().into()),
        })))?;

    // TODO: this is horrible
    let directories_with_parents: Vec<Address> = connection
        .query(Query::SingleQuery(QueryPart::Matches(PatternQuery {
            entity: QueryComponent::Variable(None),
            attribute: QueryComponent::Exact(HIER_HAS_ATTR.into()),
            value: QueryComponent::Variable(None),
        })))?
        .extract_pointers()
        .into_iter()
        .map(|(_, val)| val)
        .collect();

    Ok(all_directories
        .into_iter()
        .filter(|entry| !directories_with_parents.contains(&entry.entity))
        .map(|e| e.entity)
        .collect())
}

lazy_static! {
    static ref FETCH_CREATE_LOCK: Mutex<()> = Mutex::new(());
}

pub fn fetch_or_create_dir(
    connection: &UpEndConnection,
    parent: Option<Address>,
    directory: UNode,
    create: bool,
) -> Result<Address> {
    match parent.clone() {
        Some(address) => trace!("FETCHING/CREATING {}/{:#}", address, directory),
        None => trace!("FETCHING/CREATING /{:#}", directory),
    }

    let _lock;
    if create {
        _lock = FETCH_CREATE_LOCK.lock().unwrap();
    }

    let matching_directories = connection
        .query(Query::SingleQuery(QueryPart::Matches(PatternQuery {
            entity: QueryComponent::Variable(None),
            attribute: QueryComponent::Exact(LABEL_ATTR.into()),
            value: QueryComponent::Exact(directory.as_ref().clone().into()),
        })))?
        .into_iter()
        .map(|e: Entry| e.entity);

    let parent_has: Vec<Address> = match parent.clone() {
        Some(parent) => connection
            .query(Query::SingleQuery(QueryPart::Matches(PatternQuery {
                entity: QueryComponent::Exact(parent),
                attribute: QueryComponent::Exact(HIER_HAS_ATTR.into()),
                value: QueryComponent::Variable(None),
            })))?
            .extract_pointers()
            .into_iter()
            .map(|(_, val)| val)
            .collect(),
        None => list_roots(connection)?,
    };

    let valid_directories: Vec<Address> = matching_directories
        .filter(|a| parent_has.contains(a))
        .collect();

    match valid_directories.len() {
        0 => {
            if create {
                let new_directory_address = Address::Uuid(Uuid::new_v4());
                let type_entry = Entry {
                    entity: new_directory_address.clone(),
                    attribute: String::from(IS_OF_TYPE_ATTR),
                    value: HIER_ADDR.clone().into(),
                    provenance: "SYSTEM FS".to_string(),
                    timestamp: chrono::Utc::now().naive_utc(),
                };
                connection.insert_entry(type_entry)?;

                let directory_entry = Entry {
                    entity: new_directory_address.clone(),
                    attribute: String::from(LABEL_ATTR),
                    value: directory.as_ref().clone().into(),
                    provenance: "SYSTEM FS".to_string(),
                    timestamp: chrono::Utc::now().naive_utc(),
                };
                connection.insert_entry(directory_entry)?;

                if let Some(parent) = parent {
                    let has_entry = Entry {
                        entity: parent,
                        attribute: String::from(HIER_HAS_ATTR),
                        value: new_directory_address.clone().into(),
                        provenance: "SYSTEM FS".to_string(),
                        timestamp: chrono::Utc::now().naive_utc(),
                    };
                    connection.insert_entry(has_entry)?;
                }

                Ok(new_directory_address)
            } else {
                Err(anyhow!("Node {:?} does not exist.", directory.0))
            }
        }
        1 => Ok(valid_directories[0].clone()),
        _ => Err(anyhow!(format!(
            "Invalid database state - more than one directory matches the query {:?}/{:#}!",
            parent, directory
        ))),
    }
}

pub fn resolve_path(
    connection: &UpEndConnection,
    path: &UHierPath,
    create: bool,
) -> Result<Vec<Address>> {
    let mut result: Vec<Address> = vec![];
    let mut path_stack = path.0.to_vec();

    path_stack.reverse();
    while !path_stack.is_empty() {
        let dir_address = fetch_or_create_dir(
            connection,
            result.last().cloned(),
            path_stack.pop().unwrap(),
            create,
        )?;
        result.push(dir_address);
    }

    Ok(result)
}

pub type ResolveCache = LruCache<(Option<Address>, UNode), Address>;

pub fn resolve_path_cached(
    connection: &UpEndConnection,
    path: &UHierPath,
    create: bool,
    cache: &Arc<Mutex<ResolveCache>>,
) -> Result<Vec<Address>> {
    let mut result: Vec<Address> = vec![];
    let mut path_stack = path.0.to_vec();

    path_stack.reverse();
    while !path_stack.is_empty() {
        let node = path_stack.pop().unwrap();
        let parent = result.last().cloned();
        let key = (parent.clone(), node.clone());
        let mut cache_lock = cache.lock().unwrap();
        let cached_address = cache_lock.get(&key);
        if let Some(address) = cached_address {
            result.push(address.clone());
        } else {
            drop(cache_lock);
            let address = fetch_or_create_dir(connection, parent, node, create)?;
            result.push(address.clone());
            cache.lock().unwrap().put(key, address);
        }
    }

    Ok(result)
}

pub fn initialize_hier(connection: &UpEndConnection) -> Result<()> {
    connection.insert_entry(Entry::try_from(&*HIER_INVARIANT)?)?;
    upend_insert_addr!(connection, HIER_ADDR, IS_OF_TYPE_ATTR, TYPE_ADDR)?;
    upend_insert_val!(connection, HIER_ADDR, TYPE_HAS_ATTR, HIER_HAS_ATTR)?;
    upend_insert_val!(connection, HIER_ADDR, LABEL_ATTR, "Group")?;
    Ok(())
}

#[cfg(test)]
mod tests {
    use anyhow::Result;

    use crate::database::UpEndDatabase;
    use tempfile::TempDir;

    use super::*;

    #[test]
    fn test_unode_nonempty() {
        let node = UNode::new("foobar");
        assert!(node.is_ok());

        let node = UNode::new("");
        assert!(node.is_err());
    }

    #[test]
    fn test_path_codec() {
        let path = UHierPath(vec![
            UNode("top".to_string()),
            UNode("foo".to_string()),
            UNode("bar".to_string()),
            UNode("baz".to_string()),
        ]);

        let str_path = path.to_string();
        assert!(!str_path.is_empty());

        let decoded_path: Result<UHierPath> = str_path.parse();
        assert!(decoded_path.is_ok());

        assert_eq!(path, decoded_path.unwrap());
    }

    #[test]
    fn test_path_validation() {
        let valid_path: Result<UHierPath> = "a/b/c/d/e/f/g".parse();
        assert!(valid_path.is_ok());

        let invalid_path: Result<UHierPath> = "a/b/c//d/e/f/g".parse();
        assert!(invalid_path.is_err());

        let invalid_path: Result<UHierPath> = "a//b/c//d/e/f///g".parse();
        assert!(invalid_path.is_err());
    }

    #[test]
    fn test_path_manipulation() {
        // Initialize database
        let temp_dir = TempDir::new().unwrap();
        let open_result = UpEndDatabase::open(&temp_dir, true).unwrap();
        let connection = open_result.db.connection().unwrap();

        let foo_result = fetch_or_create_dir(&connection, None, UNode("foo".to_string()), true);
        assert!(foo_result.is_ok());
        let foo_result = foo_result.unwrap();

        let bar_result = fetch_or_create_dir(&connection, None, UNode("bar".to_string()), true);
        assert!(bar_result.is_ok());
        let bar_result = bar_result.unwrap();

        let baz_result = fetch_or_create_dir(
            &connection,
            Some(bar_result.clone()),
            UNode("baz".to_string()),
            true,
        );
        assert!(baz_result.is_ok());
        let baz_result = baz_result.unwrap();

        let roots = list_roots(&connection);
        assert_eq!(roots.unwrap(), [foo_result, bar_result.clone()]);

        let resolve_result = resolve_path(&connection, &"bar/baz".parse().unwrap(), false);

        assert!(resolve_result.is_ok());
        assert_eq!(
            resolve_result.unwrap(),
            vec![bar_result.clone(), baz_result.clone()]
        );

        let resolve_result = resolve_path(&connection, &"bar/baz/bax".parse().unwrap(), false);
        assert!(resolve_result.is_err());

        let resolve_result = resolve_path(&connection, &"bar/baz/bax".parse().unwrap(), true);
        assert!(resolve_result.is_ok());

        let bax_result = fetch_or_create_dir(
            &connection,
            Some(baz_result.clone()),
            UNode("bax".to_string()),
            false,
        );
        assert!(bax_result.is_ok());
        let bax_result = bax_result.unwrap();

        assert_eq!(
            resolve_result.unwrap(),
            vec![bar_result, baz_result, bax_result]
        );
    }
}