use crate::addressing::Address;
use crate::database::{
    bulk_retrieve_objects, file_set_valid, insert_entry, insert_file, query_entries,
    retrieve_all_files, DbPool, Entry, EntryQuery, EntryValue, InnerEntry, QueryComponent,
    DATABASE_FILENAME,
};
use crate::hash::Hashable;
use crate::models;
use crate::models::File;
use anyhow::{anyhow, Error, Result};
use chrono::prelude::*;
use diesel::sqlite::Sqlite;
use diesel::Connection;
use log::{error, info, trace};
use rayon::prelude::*;
use serde::export::Formatter;
use serde_json::Value;
use std::path::{Component, Path, PathBuf};
use std::sync::{Arc, RwLock};
use std::time::{Instant, UNIX_EPOCH};
use std::{fs, iter};
use uuid::Uuid;
use walkdir::WalkDir;

const DIR_KEY: &str = "DIR";
const DIR_HAS_KEY: &str = "DIR_HAS";

const FILE_IDENTITY_KEY: &str = "FILE_IS";
const FILENAME_KEY: &str = "FILE_NAME";

#[derive(Debug, Clone, PartialEq)]
pub struct UDirectory {
    name: String,
}

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

const TOP_SEPARATOR: &str = "//";

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

    fn from_str(string: &str) -> Result<Self, Self::Err> {
        if string.is_empty() {
            Ok(UPath(vec![]))
        } else {
            let result = match string.find(TOP_SEPARATOR) {
                Some(head_idx) => {
                    let (head, rest) = string.split_at(head_idx);
                    let mut result: Vec<UDirectory> = Vec::new();
                    result.push(UDirectory {
                        name: String::from(head),
                    });
                    result.append(
                        rest[TOP_SEPARATOR.len()..rest.len()]
                            .trim_end_matches('/')
                            .split('/')
                            .map(|part| UDirectory {
                                name: String::from(part),
                            })
                            .collect::<Vec<UDirectory>>()
                            .as_mut(),
                    );

                    result
                }
                None => string
                    .trim_end_matches('/')
                    .split('/')
                    .map(|part| UDirectory {
                        name: String::from(part),
                    })
                    .collect(),
            };

            for directory in &result {
                if directory.name.is_empty() {
                    return Err(anyhow!("INVALID PATH: Directory name cannot be empty!"));
                }
            }

            Ok(UPath(result))
        }
    }
}

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

impl std::fmt::Display for UPath {
    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
        match self.0.len() {
            0 => write!(f, ""),
            1 => write!(f, "{}", self.0.first().unwrap().name),
            _ => {
                let (head, tail) = self.0.split_first().unwrap();
                write!(
                    f,
                    "{}//{}",
                    head.name,
                    tail.iter()
                        .map(|udir| udir.name.clone())
                        .collect::<Vec<String>>()
                        .join("/")
                )
            }
        }
    }
}

trait EntryList {
    fn extract_addresses(&self) -> Vec<Address>;
}

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

pub fn list_roots<C: Connection<Backend = Sqlite>>(connection: &C) -> Result<Vec<Entry>> {
    let all_directories: Vec<Entry> = query_entries(
        connection,
        EntryQuery {
            target: QueryComponent::Any,
            key: QueryComponent::Exact(DIR_KEY.to_string()),
            value: QueryComponent::Any,
        },
    )?;

    let directories_with_parents: Vec<Address> = query_entries(
        connection,
        EntryQuery {
            target: QueryComponent::Any,
            key: QueryComponent::Exact(DIR_HAS_KEY.to_string()),
            value: QueryComponent::Any,
        },
    )?
    .extract_addresses();

    Ok(all_directories
        .into_iter()
        .filter(|entry| !directories_with_parents.contains(&entry.target))
        .collect())
}

pub async fn list_directory<C: Connection<Backend = Sqlite>>(
    connection: &C,
    path: &UPath,
) -> Result<Vec<Entry>> {
    let entry_addresses = match path.0.len() {
        0 => list_roots(connection)?
            .into_iter()
            .map(|e| e.target)
            .collect(),
        _ => {
            let resolved_path: Vec<Address> = resolve_path(connection, path, false)?;
            let last = resolved_path.last().unwrap();

            query_entries(
                connection,
                EntryQuery {
                    target: QueryComponent::Exact(last.clone()),
                    key: QueryComponent::Exact(DIR_HAS_KEY.to_string()),
                    value: QueryComponent::Any,
                },
            )?
            .extract_addresses()
        }
    };

    Ok(bulk_retrieve_objects(connection, entry_addresses)?
        .into_iter()
        .filter(|e| [DIR_KEY, FILENAME_KEY, FILE_IDENTITY_KEY].contains(&e.key.as_str()))
        .collect::<Vec<Entry>>())
}

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

    let dir_value = EntryValue::Value(Value::String(directory.name));
    let directories: Vec<Address> = query_entries(
        connection,
        EntryQuery {
            target: QueryComponent::Any,
            key: QueryComponent::Exact(String::from(DIR_KEY)),
            value: QueryComponent::Exact(dir_value.clone()),
        },
    )?
    .into_iter()
    .map(|e: Entry| e.target)
    .collect();

    let valid_directories: Vec<Address> = match parent.clone() {
        Some(address) => {
            let parent_has: Vec<Address> = query_entries(
                connection,
                EntryQuery {
                    target: QueryComponent::Exact(address),
                    key: QueryComponent::Exact(String::from(DIR_HAS_KEY)),
                    value: QueryComponent::Any,
                },
            )?
            .extract_addresses();

            directories
                .into_iter()
                .filter(|a| parent_has.contains(a))
                .collect()
        }
        None => directories,
    };

    match valid_directories.len() {
        0 => {
            if create {
                let new_directory_address = Address::UUID(Uuid::new_v4());
                let directory_entry = InnerEntry {
                    target: new_directory_address.clone(),
                    key: String::from(DIR_KEY),
                    value: dir_value,
                };
                let _ = insert_entry(connection, directory_entry)?;

                if let Some(parent_addr) = parent {
                    let has_entry = InnerEntry {
                        target: parent_addr,
                        key: String::from(DIR_HAS_KEY),
                        value: EntryValue::Address(new_directory_address.clone()),
                    };
                    let _ = insert_entry(connection, has_entry)?;
                }

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

pub fn resolve_path<C: Connection<Backend = Sqlite>>(
    connection: &C,
    path: &UPath,
    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 async fn reimport_directory(pool: DbPool, directory: PathBuf) {
    let result = actix_web::web::block(move || _reimport_directory(pool, directory)).await;
    if result.is_err() {
        let err = result.err().unwrap();
        error!("Update did not succeed! {}", err);
    }
}

type UpdatePathResult = Result<UpdatePathOutcome>;

enum UpdatePathOutcome {
    Added(PathBuf),
    Unchanged(PathBuf),
    Removed(PathBuf),
}

fn _reimport_directory<T: AsRef<Path>>(
    pool: DbPool,
    directory: T,
) -> Result<Vec<UpdatePathResult>> {
    let start = Instant::now();

    let path_entries: Vec<PathBuf> = WalkDir::new(&directory)
        .into_iter()
        .filter_map(|e| e.ok())
        .filter(|e| e.path().is_file() && e.file_name() != DATABASE_FILENAME)
        .map(|e| fs::canonicalize(e.into_path()).unwrap())
        .collect();

    let rw_pool = Arc::new(RwLock::new(pool.clone()));
    let absolute_path = fs::canonicalize(&directory)?;
    let existing_files = Arc::new(RwLock::new(retrieve_all_files(&pool.get()?)?));

    let path_results: Vec<UpdatePathResult> = path_entries
        .into_par_iter()
        .map(|path| {
            Ok(_process_directory_entry(
                &rw_pool,
                path,
                &absolute_path,
                &existing_files,
            )?)
        })
        .collect();

    let cleanup_results: Vec<UpdatePathResult> = existing_files
        .write()
        .unwrap()
        .iter()
        .filter(|f| f.valid)
        .map(|file| {
            let connection = pool.get()?;
            connection.transaction::<_, Error, _>(|| {
                let _ = file_set_valid(&connection, file.id, false)?;
                // remove_object(&connection, )?
                Ok(UpdatePathOutcome::Removed(PathBuf::from(file.path.clone())))
            })
        })
        .collect();

    info!(
        "Finished updating {}. Took {}s.",
        directory.as_ref().display(),
        start.elapsed().as_secs()
    );

    Ok(path_results
        .into_iter()
        .chain(cleanup_results.into_iter())
        .collect())
}

fn _process_directory_entry<P: AsRef<Path>>(
    db_pool: &Arc<RwLock<DbPool>>,
    path: PathBuf,
    directory_path: &P,
    existing_files: &Arc<RwLock<Vec<File>>>,
) -> UpdatePathResult {
    info!("Processing: {:?}", path);

    let db_pool = Arc::clone(&db_pool);
    let existing_files = Arc::clone(&existing_files);

    let normalized_path = path.strip_prefix(&directory_path)?;
    let normalized_path_str = normalized_path.to_str().expect("path not valid unicode?!");

    let metadata = fs::metadata(&path)?;
    let size = metadata.len() as i64;
    if size < 0 {
        panic!("File {} too large?!", path.display());
    }
    let mtime = metadata
        .modified()
        .map(|t| {
            NaiveDateTime::from_timestamp(t.duration_since(UNIX_EPOCH).unwrap().as_secs() as i64, 0)
        })
        .ok();

    {
        let mut existing_files = existing_files.write().unwrap();

        let maybe_existing_file = existing_files
            .iter()
            .enumerate()
            .find(|(_, file)| file.path == normalized_path_str);

        if let Some((idx, existing_file)) = maybe_existing_file {
            if size == existing_file.size && mtime == existing_file.mtime {
                if !existing_file.valid {
                    let _ =
                        file_set_valid(&db_pool.write().unwrap().get()?, existing_file.id, true)?;
                }
                existing_files.remove(idx);
                return Ok(UpdatePathOutcome::Unchanged(path));
            }
        }
    }

    let digest = path.hash()?;

    let new_file = models::NewFile {
        path: normalized_path_str.to_string(),
        hash: (digest.clone()).0,
        added: NaiveDateTime::from_timestamp(Utc::now().timestamp(), 0),
        size,
        mtime,
    };

    let _ = insert_file(&db_pool.write().unwrap().get()?, new_file)?;

    let components = normalized_path.components().collect::<Vec<Component>>();
    let (filename, dir_path) = components.split_last().unwrap();

    let upath = UPath(
        iter::once(UDirectory {
            name: "NATIVE".to_string(),
        })
        .chain(dir_path.iter().map(|component| UDirectory {
            name: component.as_os_str().to_string_lossy().to_string(),
        }))
        .collect(),
    );
    let resolved_path = resolve_path(&db_pool.write().unwrap().get()?, &upath, true)?;
    let parent_dir = resolved_path.last().unwrap();

    let _pool = &db_pool.write().unwrap();
    let connection = _pool.get()?;
    connection.transaction::<_, Error, _>(|| {
        let file_address = Address::UUID(Uuid::new_v4());

        let name_entry = InnerEntry {
            target: file_address.clone(),
            key: FILENAME_KEY.to_string(),
            value: EntryValue::Value(Value::String(
                filename.as_os_str().to_string_lossy().to_string(),
            )),
        };
        let _ = insert_entry(&connection, name_entry)?;

        let identity_entry = InnerEntry {
            target: file_address.clone(),
            key: FILE_IDENTITY_KEY.to_string(),
            value: EntryValue::Address(Address::Hash(digest.clone())),
        };

        let _ = insert_entry(&connection, identity_entry)?;

        let dir_has_entry = InnerEntry {
            target: parent_dir.clone(),
            key: DIR_HAS_KEY.to_string(),
            value: EntryValue::Address(file_address),
        };
        let _ = insert_entry(&connection, dir_has_entry)?;

        Ok(UpdatePathOutcome::Added(path.clone()))
    })
}

pub fn lookup_by_filename<C: Connection<Backend = Sqlite>>(
    connection: &C,
    filename: String,
) -> Result<Vec<Entry>> {
    let dir_value = EntryValue::Value(Value::String(filename));
    let entity_addresses = query_entries(
        connection,
        EntryQuery {
            target: QueryComponent::Any,
            key: QueryComponent::In(vec![DIR_KEY.to_string(), FILENAME_KEY.to_string()]), // ?
            value: QueryComponent::ILike(dir_value),
        },
    )?;

    bulk_retrieve_objects(
        connection,
        entity_addresses.into_iter().map(|e| e.target).collect(),
    )
}

#[cfg(test)]
mod tests {
    use crate::filesystem::{UDirectory, UPath};
    use anyhow::Result;

    #[test]
    fn test_path_codec() {
        let path = UPath(vec![
            UDirectory {
                name: "top".to_string(),
            },
            UDirectory {
                name: "foo".to_string(),
            },
            UDirectory {
                name: "bar".to_string(),
            },
            UDirectory {
                name: "baz".to_string(),
            },
        ]);

        let str_path = path.to_string();
        assert!(str_path.len() > 0);

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

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

    #[test]
    fn test_validation() {
        let invalid_path: Result<UPath> = "a//b/c//d/e/f///g".parse();
        assert!(invalid_path.is_err())
    }
}