use super::{DBError, FileData};
use std::{collections::HashMap, slice, str};

#[derive(Clone)]
pub struct Databases {
    db_map: HashMap<String, String>,
}

impl Databases {
    pub fn new() -> Self {
        Self {
            db_map: HashMap::new(),
        }
    }

    fn add_database(&mut self, name: &str, id: &str) -> Result<String, DBError> {
        if name.len() == 0 {
            return Err(DBError::new("database names cannot be empty"));
        } else if self.db_map.contains_key(name) {
            return Err(DBError::new("database already exists"));
        } else {
            self.db_map.insert(name.to_string(), id.to_string());
            Ok(id.to_string())
        }
    }

    fn get_database(&self, name: &str) -> Option<String> {
        self.db_map.get(name).cloned()
    }

    fn show(&self) -> Vec<String> {
        let mut names: Vec<String> = self.db_map.clone().into_keys().collect();
        names.sort();
        names
    }
}

impl FileData<Self> for Databases {
    fn to_bytes(&self) -> Vec<u8> {
        let mut output = Vec::new();
        for (name, id) in self.db_map.iter() {
            output.append(&mut name.as_bytes().to_vec());
            output.push(0);
            output.append(&mut id.as_bytes().to_vec());
            output.push(0);
        }
        output
    }

    fn from_bytes(data: &mut slice::Iter<u8>) -> Result<Self, DBError> {
        let mut output = Databases::new();
        let mut name: Vec<u8> = Vec::new();
        let mut id: Vec<u8> = Vec::new();
        let mut get_id = false;
        let mut letter: u8;
        loop {
            match data.next() {
                Some(a) => letter = a.clone(),
                None => {
                    if !name.is_empty() {
                        return Err(DBError::new("file corruption"));
                    }
                    break;
                }
            }
            if letter == 0 {
                if get_id {
                    match output
                        .add_database(str::from_utf8(&name).unwrap(), str::from_utf8(&id).unwrap())
                    {
                        Ok(_) => (),
                        Err(err) => {
                            let mut error = DBError::new("file corruption");
                            error.add_source(err);
                            return Err(error);
                        }
                    };
                    name.clear();
                    id.clear();
                }
                get_id = !get_id;
            } else {
                if get_id {
                    id.push(letter);
                } else {
                    name.push(letter);
                }
            }
        }
        Ok(output)
    }
}

#[cfg(test)]
mod functions {
    use super::*;

    #[test]
    fn add_entry() {
        let name = "fred";
        let id = "123456";
        let mut dbs = Databases::new();
        let output = dbs.add_database(name, id).unwrap();
        assert_eq!(output, id.to_string());
    }

    #[test]
    fn add_entry_no_name() {
        let name = "";
        let id = "123456";
        let mut dbs = Databases::new();
        match dbs.add_database(name, id) {
            Ok(_) => assert!(false, "There should have been an error"),
            Err(err) => assert_eq!(err.to_string(), "database names cannot be empty"),
        }
    }

    #[test]
    fn entry_cannot_be_over_written() {
        let name = "barney";
        let id = "abcde";
        let mut dbs = Databases::new();
        dbs.add_database(name, id).unwrap();
        match dbs.add_database(name, "09876") {
            Ok(_) => assert!(false, "There should have been an error"),
            Err(err) => assert_eq!(err.to_string(), "database already exists"),
        }
        let output = dbs.get_database(name);
        assert_eq!(output, Some(id.to_string()));
    }

    #[test]
    fn get_bad_database() {
        let dbs = Databases::new();
        let output = dbs.get_database("missing");
        assert_eq!(output, None);
    }

    #[test]
    fn list_databases() {
        let mut dbs = Databases::new();
        dbs.add_database("zebra", "a").unwrap();
        dbs.add_database("alpha", "a").unwrap();
        dbs.add_database("charlie", "a").unwrap();
        dbs.add_database("wilma", "a").unwrap();
        dbs.add_database("frank", "a").unwrap();
        let expected = ["alpha", "charlie", "frank", "wilma", "zebra"];
        let output = dbs.show();
        assert_eq!(output, expected);
    }
}

#[cfg(test)]
mod filedata {
    use super::*;
    use std::error::Error;

    #[test]
    fn to_bytes_new() {
        let dbs = Databases::new();
        let expected: Vec<u8> = Vec::new();
        let output = dbs.to_bytes();
        assert_eq!(output, expected);
    }

    #[test]
    fn to_bytes_with_database() {
        let mut dbs = Databases::new();
        let name = "something";
        let id = "id";
        dbs.add_database(name, id).unwrap();
        let mut expected: Vec<u8> = Vec::new();
        expected.append(&mut name.as_bytes().to_vec());
        expected.push(0);
        expected.append(&mut id.as_bytes().to_vec());
        expected.push(0);
        let output = dbs.to_bytes();
        assert_eq!(output, expected);
    }

    #[test]
    fn from_bytes() {
        let mut dbs = Databases::new();
        dbs.add_database("one", "1").unwrap();
        dbs.add_database("two", "2").unwrap();
        dbs.add_database("three", "3").unwrap();
        let data = dbs.to_bytes();
        let mut feed = data.iter();
        let output = Databases::from_bytes(&mut feed).unwrap();
        assert_eq!(output.db_map, dbs.db_map);
    }

    #[test]
    fn from_bytes_incomplete_name() {
        let data = "notName".as_bytes();
        let mut feed = data.iter();
        match Databases::from_bytes(&mut feed) {
            Ok(_) => assert!(false, "This should have failed."),
            Err(err) => assert_eq!(err.to_string(), "file corruption"),
        }
    }

    #[test]
    fn from_bytes_incomplete_id() {
        let mut data = "proper".as_bytes().to_vec();
        data.push(0);
        data.append(&mut "nope".as_bytes().to_vec());
        let mut feed = data.iter();
        match Databases::from_bytes(&mut feed) {
            Ok(_) => assert!(false, "This should have failed."),
            Err(err) => assert_eq!(err.to_string(), "file corruption"),
        }
    }

    #[test]
    fn from_bytes_handles_error() {
        let mut data = "duplicate".as_bytes().to_vec();
        data.push(0);
        data.append(&mut "first".as_bytes().to_vec());
        data.push(0);
        data.append(&mut "duplicate".as_bytes().to_vec());
        data.push(0);
        data.append(&mut "second".as_bytes().to_vec());
        data.push(0);
        let mut feed = data.iter();
        match Databases::from_bytes(&mut feed) {
            Ok(_) => assert!(false, "This should have failed."),
            Err(err) => {
                assert_eq!(err.to_string(), "file corruption");
                assert!(
                    err.source().is_some(),
                    "Should state file corruption cause."
                );
                assert_eq!(err.source().unwrap().to_string(), "database already exists")
            }
        }
    }
}