use crate::models::{Entry, Keyword, NewEntry, NewKeyword};
use diesel::pg::PgConnection;
use diesel::prelude::*;
use failure::format_err;
use failure::Error;
use std::borrow::Cow;

/// Maximum number of times we'll follow a `see: ` pointer.
const RECURSION_LIMIT: usize = 5;

pub struct KeywordDetails {
    pub keyword: Keyword,
    pub entries: Vec<Entry>,
}

impl KeywordDetails {
    pub fn learn(&mut self, nick: &str, text: &str, dbc: &PgConnection) -> Result<usize, Error> {
        let now = ::chrono::Utc::now().naive_utc();
        let ins = NewEntry {
            keyword_id: self.keyword.id,
            idx: (self.entries.len() + 1) as _,
            text,
            creation_ts: now,
            created_by: nick,
        };
        let new = {
            use crate::schema::entries;
            ::diesel::insert_into(entries::table)
                .values(ins)
                .get_result(dbc)?
        };
        self.entries.push(new);
        Ok(self.entries.len())
    }

    pub fn process_moves(&mut self, moves: &[(i32, i32)], dbc: &PgConnection) -> Result<(), Error> {
        for (oid, new_idx) in moves {
            {
                use crate::schema::entries::dsl::*;
                ::diesel::update(entries.filter(id.eq(oid)))
                    .set(idx.eq(new_idx))
                    .execute(dbc)?;
            }
        }
        self.entries = Self::get_entries(self.keyword.id, dbc)?;
        Ok(())
    }

    pub fn swap(&mut self, idx_a: usize, idx_b: usize, dbc: &PgConnection) -> Result<(), Error> {
        let mut moves = vec![];
        for ent in self.entries.iter() {
            if ent.idx == idx_a as i32 {
                moves.push((ent.id, idx_b as i32));
            }
            if ent.idx == idx_b as i32 {
                moves.push((ent.id, idx_a as i32));
            }
        }
        if moves.len() != 2 {
            Err(format_err!("Invalid swap operation."))?;
        }
        self.process_moves(&moves, dbc)?;
        Ok(())
    }

    pub fn update(&mut self, idx: usize, val: &str, dbc: &PgConnection) -> Result<(), Error> {
        let ent = self
            .entries
            .get_mut(idx.saturating_sub(1))
            .ok_or(format_err!("No such element to update."))?;
        {
            use crate::schema::entries::dsl::*;
            ::diesel::update(entries.filter(id.eq(ent.id)))
                .set(text.eq(val))
                .execute(dbc)?;
        }
        ent.text = val.to_string();
        Ok(())
    }

    pub fn delete(&mut self, idx: usize, dbc: &PgConnection) -> Result<(), Error> {
        // step 1: delete the element
        {
            let ent = self
                .entries
                .get(idx.saturating_sub(1))
                .ok_or(format_err!("No such element to delete."))?;
            {
                use crate::schema::entries::dsl::*;
                ::diesel::delete(entries.filter(id.eq(ent.id))).execute(dbc)?;
            }
        }
        // step 2: move all the elements in front of it back one
        let mut moves = vec![];
        for ent in self.entries.iter() {
            if idx > ent.idx as _ {
                moves.push((ent.id, ent.idx.saturating_sub(1)));
            }
        }
        self.process_moves(&moves, dbc)?;
        Ok(())
    }

    pub fn add_zwsp_to_name(name: &str) -> Option<String> {
        let second_index = name.char_indices().nth(1).map(|(i, _)| i)?;
        let (start, end) = name.split_at(second_index);
        Some(format!("{}​{}", start, end))
    }

    pub fn format_entry(&self, idx: usize) -> Option<String> {
        if let Some(ent) = self.entries.get(idx.saturating_sub(1)) {
            let gen_clr = if self.keyword.chan == "*" {
                "\x0307"
            } else {
                ""
            };
            let zwsp_name = Self::add_zwsp_to_name(&self.keyword.name)
                .unwrap_or_else(|| self.keyword.name.clone());
            Some(format!(
                "\x02{}{}\x0f\x0315[{}/{}]\x0f: {} \x0f\x0314[{}]\x0f",
                gen_clr,
                zwsp_name,
                idx,
                self.entries.len(),
                ent.text,
                ent.creation_ts.date()
            ))
        } else {
            None
        }
    }

    pub fn get_or_create(word: &str, c: &str, dbc: &PgConnection) -> Result<Self, Error> {
        if let Some(ret) = Self::get(word, c, dbc)? {
            Ok(ret)
        } else {
            Ok(Self::create(word, c, dbc)?)
        }
    }

    pub fn create(word: &str, c: &str, dbc: &PgConnection) -> Result<Self, Error> {
        let val = NewKeyword {
            name: word,
            chan: c,
        };
        let ret: Keyword = {
            use crate::schema::keywords;
            ::diesel::insert_into(keywords::table)
                .values(val)
                .get_result(dbc)?
        };
        Ok(KeywordDetails {
            keyword: ret,
            entries: vec![],
        })
    }

    fn get_entries(kid: i32, dbc: &PgConnection) -> Result<Vec<Entry>, Error> {
        let entries: Vec<Entry> = {
            use crate::schema::entries::dsl::*;
            entries
                .filter(keyword_id.eq(kid))
                .order_by(idx.asc())
                .load(dbc)?
        };
        Ok(entries)
    }

    fn get_inner<'a, T: Into<Cow<'a, str>>>(
        word: T,
        c: &str,
        dbc: &PgConnection,
        recursion_count: usize,
    ) -> Result<Option<Self>, Error> {
        let word = word.into();
        let keyword: Option<Keyword> = {
            use crate::schema::keywords::dsl::*;
            keywords
                .filter(name.ilike(word).and(chan.eq(c).or(chan.eq("*"))))
                .first(dbc)
                .optional()?
        };
        if let Some(k) = keyword {
            let entries = Self::get_entries(k.id, dbc)?;
            if let Some(e0) = entries.get(0) {
                if e0.text.starts_with("see: ") {
                    if recursion_count > RECURSION_LIMIT {
                        // Oh dear.
                        Err(format_err!("Halt. You're having a bit too much fun."))?
                    }
                    let new_word = e0.text.replace("see: ", "");
                    return Self::get_inner(new_word, c, dbc, recursion_count + 1);
                }
            }
            Ok(Some(KeywordDetails {
                keyword: k,
                entries,
            }))
        } else {
            Ok(None)
        }
    }

    pub fn get<'a, T: Into<Cow<'a, str>>>(
        word: T,
        c: &str,
        dbc: &PgConnection,
    ) -> Result<Option<Self>, Error> {
        Self::get_inner(word, c, dbc, 0)
    }
}