use crate::city;
use crate::db::{LayoutDB, SavedLayout, MergeLowerBound};
use crate::city::{City, House, SIZE};
use itertools::Itertools;
use itertools::iproduct;
use std::collections::{VecDeque, HashMap};
use std::collections::vec_deque::Iter;

struct LeftState<'a> {
    layout: &'a SavedLayout,
    sorted_houses: Vec<House>,
    line: LeftLine
}

struct RightState<'a> {
    layout: &'a SavedLayout,
    line: RightLine
}

pub struct CompatibilityCache {
    map: HashMap<(usize, usize, usize, usize, bool), bool>
}

impl CompatibilityCache {
    pub fn new() -> CompatibilityCache {
        CompatibilityCache {
            map: HashMap::new()
        }
    }

    pub fn is_compatible(&self, left_layout: &SavedLayout, right_layout: &SavedLayout, left_update_index: usize, right_update_index: usize, y_axis: bool) -> Option<&bool> {
        self.map.get(&(left_layout.id(), right_layout.id(), left_update_index, right_update_index, y_axis))
    }

    pub fn set_compatible(&mut self, left_layout: &SavedLayout, right_layout: &SavedLayout, left_update_index: usize, right_update_index: usize, y_axis: bool, compatible: bool) {
        self.map.insert((left_layout.id(), right_layout.id(), left_update_index, right_update_index, y_axis), compatible);
    }
}

pub fn create_new_best_combination(city: &City, left_layouts: &Vec<SavedLayout>, right_layouts: &Vec<SavedLayout>, db: &mut LayoutDB, cache: &mut CompatibilityCache, transposed: bool) -> bool {
    let mut best_price = left_layouts.iter().chain(right_layouts.iter())
        .map(|layout| city::get_price(&city, layout.houses()))
        .min();

    let mut improved = false;

    let mut lefts = Vec::new();
    let mut rights = Vec::new();

    for left_layout in left_layouts {
        // We make sure that there is at least one other layout we want to compare this one with
        // to avoid unnecessary house updates
        let mut needed = false;
        for right_layout in right_layouts {
            if let Some(bound) = db.get_merge_lower_bound(left_layout, right_layout, transposed) {
                if bound < best_price.expect("No best price set while lower bounds exist") {
                    eprintln!("Low bound; left needed ({} - {})", left_layout.id(), right_layout.id());
                    needed = true;
                    break;
                }
            } else {
                eprintln!("No bound; left needed ({} - {})", left_layout.id(), right_layout.id());
                needed = true;
                break;
            }
        }

        if !needed {
            continue;
        }

        // Sorted in reverse so we can remove from the end
        let sorted_houses: Vec<_> = left_layout.houses().iter().sorted_by(|h1, h2| h2.x.cmp(&h1.x)).map(|x| *x).collect();

        lefts.push(LeftState {
            layout: &left_layout,
            sorted_houses,
            line: LeftLine::new()
        });
    }

    for right_layout in right_layouts {
        // We make sure that there is at least one other layout we want to compare this one with
        // to avoid unnecessary house updates
        let mut needed = false;
        for left_layout in left_layouts {
            if let Some(bound) = db.get_merge_lower_bound(left_layout, right_layout, transposed) {
                if bound < best_price.expect("No best price set while lower bounds exist") {
                    needed = true;
                }
            } else {
                needed = true;
            }
        }

        if !needed {
            continue;
        }

        let mut sorted_houses: Vec<_> = right_layout.houses().iter().sorted_by(|h1, h2| h2.x.cmp(&h1.x)).map(|x| *x).collect();

        let mut line = RightLine::new();
        // Make sure that we include all houses initially
        while let Some(house) = sorted_houses.pop() {
            line.add_house(house, &city);
        }
        rights.push(RightState {
            layout: right_layout,
            line
        });
    }

    let axis = if transposed { "y" } else { "x" };

    // x is the last left coordinate, x+1 is right
    for x in 0..SIZE {
        eprintln!("Starting {} {}", axis, x);

        // Update the lines
        for left in lefts.iter_mut() {
            while let Some(house) = left.sorted_houses.last() {
                if house.x == x {
                    left.line.add_house(*house, &city);
                    left.sorted_houses.pop();
                } else {
                    break;
                }
            }
        }

        for right_line in rights.iter_mut() {
            right_line.line.remove_houses(x, &city);
        }

        // Check compatibility of lines
        if x == 0 {
            // Cannot check this due to limitations in the implementation of LeftLine,
            // it wouldn't be very interesting anyway.
            continue;
        }

        let pairs = iproduct!(lefts.iter().enumerate(), rights.iter().enumerate())
            .filter(|((left_i, _), (right_i, _))| left_i != right_i)
            .filter(|((_, left), (_, right))| {
                if let Some(bound) = db.get_merge_lower_bound(left.layout, right.layout, transposed) {
                    if bound >= best_price.expect("No best price set while lower bounds exist") {
                        return false;
                    }
                }
                return true;
            })
            .map(|((left_i, left), (right_i, right))| (left, right, left.line.price + right.line.price, left_i, right_i))
            .sorted_by(|(_, _, price1, _, _), (_, _, price2, _, _)| price1.cmp(&price2));

        let mut compatibles = 0;
        let mut incompatibles = 0;
        let mut cache_hits = 0;
        for (left, right, price, left_i, right_i) in pairs {
            if let Some(min_price) = best_price {
                if price >= min_price {
                    break;
                }
            }
            let compatible = match cache.is_compatible(left.layout, right.layout, left.line.last_update_x, right.line.last_update_x, transposed) {
                None => {
                    let compatible = is_compatible(city, &left.line, &right.line);
                    cache.set_compatible(left.layout, right.layout, left.line.last_update_x, right.line.last_update_x, transposed, compatible);
                    compatible
                }
                Some(compatible) => {
                    cache_hits += 1;
                    *compatible
                }
            };
            if compatible {
                if best_price.is_none() || price < best_price.unwrap() {
                    best_price = Some(price);
                    eprintln!("{} - new best score, cut on {} {}, left {} - right {}, printing", price, axis, x, left_i, right_i);
                    println!("{} - new best score, cut on {} {}, left {} - right {}", price, axis, x, left_i, right_i);
                    let mut new_houses: Vec<_> = left.line.houses().copied().chain(right.line.houses().copied()).collect();
                    if transposed {
                        new_houses = transpose_layout(&new_houses);
                    }
                    println!("{}", new_houses.len());
                    for house in &new_houses {
                        println!("{} {}", house.y, house.x);
                    }

                    // We only add best results to avoid overfilling the database with similar layouts
                    db.add_layout(&new_houses, false);
                    improved = true;
                }
                compatibles += 1;

                // All other pairs would be more expensive
                break;
            } else {
                incompatibles += 1;
            }
        }

        eprintln!("{} incompatibles checked before {} compatible ({} cache hits)", incompatibles, compatibles, cache_hits);
    }

    if let Some(lowest_price) = best_price {
        let mut new_bounds = Vec::new();

        for left_layout in left_layouts {
            for right_layout in right_layouts {
                new_bounds.push(MergeLowerBound::new(left_layout.id(), right_layout.id(), transposed, lowest_price));
            }
        }
        db.add_merge_lower_bounds(new_bounds);
    }

    improved
}

fn is_compatible(city: &City, left: &LeftLine, right: &RightLine) -> bool {
    for y in 0..SIZE {
        let max_left_covered_x = left.get_max_covered_x(y);
        let min_right_covered_x = right.get_min_covered_x(y);

        // This range will often be empty
        for x in (max_left_covered_x + 1)..min_right_covered_x {
            if city.is_house_xy(x, y) {
                return false;
            }
        }
    }

    true
}

struct LeftLine {
    covers: Vec<usize>,
    houses: Vec<House>,
    price: u32,
    last_update_x: usize
}

struct RightLine {
    covers: Vec<usize>,
    houses: VecDeque<House>,
    price: u32,
    last_update_x: usize
}

impl LeftLine {
    pub fn new() -> Self {
        // XXX: Careful, default of 0 includes covering first vertical line
        let covers = vec![0; SIZE];
        let houses = Vec::new();
        LeftLine { covers, houses, price: 0, last_update_x: 0 }
    }

    pub fn add_house(&mut self, house: House, city: &City) {
        let range_rect = house.range_rectangle();
        for y in range_rect.top..=range_rect.bottom {
            // Should always be the max variant
            self.covers[y] = self.covers[y].max(range_rect.right);
        }
        self.price += city.get_price(house) as u32;
        self.houses.push(house);
        self.last_update_x = house.x;
    }

    pub fn get_max_covered_x(&self, y: usize) -> usize {
        self.covers[y]
    }

    pub fn get_side_price(&self) -> u32 {
        self.price
    }

    pub fn houses(&self) -> std::slice::Iter<'_, House> {
        self.houses.iter()
    }
}

impl RightLine {
    pub fn new() -> Self {
        let covers = vec![usize::MAX; SIZE];
        let houses = VecDeque::new();
        RightLine { covers, houses, price: 0, last_update_x: 0 }
    }

    pub fn add_house(&mut self, house: House, city: &City) {
        // Added houses have to always be ordered by x
        let range_rect = house.range_rectangle();
        for y in range_rect.top..=range_rect.bottom {
            self.covers[y] = self.covers[y].min(range_rect.left);
        }

        self.houses.push_back(house);
        self.price += city.get_price(house) as u32;
        self.last_update_x = house.x;
    }

    pub fn remove_houses(&mut self, x: usize, city: &City) {
        // Has to be called with x, x+1, x+2...
        while let Some(house) = self.houses.front() {
            if house.x == x {
                let removed_house = self.houses.pop_front().unwrap();
                let removed_rect = removed_house.range_rectangle();

                // Remove the now-outdated distances around the removed house
                for y in removed_rect.top..=removed_rect.bottom {
                    self.covers[y] = usize::MAX;
                }

                // Update distances around the removed house if the area of any houses
                // intersects the removed area
                for house in &self.houses {
                    let house_rect = house.range_rectangle();
                    let y_intersection = if removed_house.y < house.y {
                        house_rect.top..=removed_rect.bottom
                    } else {
                        removed_rect.top..=house_rect.bottom
                    };

                    for y in y_intersection {
                        self.covers[y] = self.covers[y].min(house_rect.left);
                    }
                }

                self.price -= city.get_price(removed_house) as u32;
                self.last_update_x = removed_house.x;
            } else {
                break;
            }
        }
    }

    pub fn get_min_covered_x(&self, y: usize) -> usize {
        self.covers[y].min(SIZE)
    }

    pub fn get_side_price(&self) -> u32 {
        self.price
    }

    pub fn houses(&self) -> Iter<'_, House> {
        self.houses.iter()
    }
}

pub fn transpose_layout(houses: &Vec<House>) -> Vec<House> {
    let mut transposed = Vec::new();
    for house in houses {
        transposed.push(House::new(house.y, house.x));
    }

    transposed
}