use alloc::collections::BTreeMap;
use alloc::vec::Vec;

use binary_serde::{BinarySerde, DeserializeError, Endianness};

//use crate::card::model::Nfcraw_card;

use crate::card::model::RawCard;
use crate::storage::store::{Store, StoreError};

use crate::storage::{CARDSTORE_REGION, MemoryRegion};

const MAX_CARDS: usize = 20000;

const COUNT_REGION: MemoryRegion = MemoryRegion {
    offset: CARDSTORE_REGION.offset,
    size: size_of::<u32>(),
};

#[derive(Debug, BinarySerde, PartialEq, Eq, Clone)]
#[repr(C)]
pub struct AllocationTableEntry {
    uuid: u32,
    // this is the numeric offset of the AllocationTableEntry
    // as well as the card entry in flash memory
    // size_of::<AllocationTableEntry>() * offset
    // size_of::<RawCard>() * offset
    offset: u32,

    creation_date: u64,
    last_read_date: u64,

    // how often a card has been read by nfc
    read_count: u32,

    deleted: bool,

    reserved: [u64; 4],
}

impl AllocationTableEntry {
    fn new(uuid: u32, offset: u32, timestamp: u64) -> Self {
        Self {
            uuid,
            offset,
            creation_date: timestamp,
            last_read_date: timestamp,
            read_count: 0,
            deleted: true,
            reserved: [0; 4],
        }
    }
}

const ALLOCATION_TABLE_REGION: MemoryRegion = MemoryRegion {
    offset: COUNT_REGION.end() as u32,
    size: MAX_CARDS * AllocationTableEntry::SERIALIZED_SIZE,
};

const CARDS_REGION: MemoryRegion = MemoryRegion {
    offset: ALLOCATION_TABLE_REGION.end() as u32,
    size: CARDSTORE_REGION.size - ALLOCATION_TABLE_REGION.end(),
};

#[derive(Debug)]
pub enum CardStoreError {
    Store(StoreError),
    CorruptedEntry(DeserializeError),
    NoEntry,
}

impl From<StoreError> for CardStoreError {
    fn from(error: StoreError) -> CardStoreError {
        CardStoreError::Store(error)
    }
}

impl From<DeserializeError> for CardStoreError {
    fn from(error: DeserializeError) -> CardStoreError {
        CardStoreError::CorruptedEntry(error)
    }
}

pub struct CardStore {
    store: Store,
    count: u32,
    pub allocation_table: BTreeMap<u32, AllocationTableEntry>,
}

impl CardStore {
    pub fn new(mut store: Store) -> Result<Self, CardStoreError> {
        let mut count_bytes: [u8; COUNT_REGION.size] = [0; COUNT_REGION.size];

        store.read(COUNT_REGION.offset, &mut count_bytes)?;

        let count: u32 = u32::from_ne_bytes(count_bytes);

        let mut allocation_table_entries: Vec<u8> =
            Vec::with_capacity(AllocationTableEntry::SERIALIZED_SIZE * count as usize);

        store.read(
            ALLOCATION_TABLE_REGION.offset,
            &mut allocation_table_entries,
        )?;

        let chunks =
            allocation_table_entries.into_chunks::<{ AllocationTableEntry::SERIALIZED_SIZE }>();

        let mut allocation_table = BTreeMap::<u32, AllocationTableEntry>::new();
        for chunk in chunks {
            let allocation_table_entry =
                AllocationTableEntry::binary_deserialize(chunk.as_ref(), Endianness::Little)?;
            allocation_table.insert(allocation_table_entry.uuid, allocation_table_entry);
        }

        Ok(Self {
            store,
            count,
            allocation_table,
        })
    }

    pub fn get_card_by_uuid(&mut self, uuid: u32) -> Result<RawCard, CardStoreError> {
        let entry = self
            .allocation_table
            .get(&uuid)
            .ok_or(CardStoreError::NoEntry)?;

        let mut raw_card: [u8; size_of::<RawCard>()] = [0; size_of::<RawCard>()];
        self.store.read(entry.offset, &mut raw_card)?;

        Ok(RawCard::binary_deserialize(
            raw_card.as_ref(),
            Endianness::Little,
        )?)
    }

    pub fn save_raw_card(
        &mut self,
        raw_card: RawCard,
        timestamp: u64,
    ) -> Result<(), CardStoreError> {
        let uuid: u32 = (u16::from_ne_bytes(raw_card.event_encoding) as u32) << 16
            | (u16::from_ne_bytes(raw_card.card_uuid) as u32);
        log::info!("Saving card with uuid {:x}", uuid);

        // check if we already got the card
        // if not find the next deleted entry,
        // if none create a new one at the end
        let (entry, is_new) = match self.allocation_table.get_mut(&uuid) {
            Some(entry) => {
                log::debug!("old entry");
                (entry, false)
            }
            None => match self
                .allocation_table
                .values_mut()
                .find(|entry| entry.deleted)
            {
                Some(entry) => {
                    log::debug!("deleted entry");
                    (entry, true)
                }
                None => {
                    log::debug!("new entry");
                    let entry = AllocationTableEntry::new(uuid, self.count + 1, timestamp);
                    self.allocation_table.insert(uuid, entry);
                    (
                        self.allocation_table
                            .get_mut(&uuid)
                            .expect("entry was just inserted"),
                        true,
                    )
                }
            },
        };

        // only write card data if it is new. else it is already written in flash
        if is_new {
            log::debug!("writing RawCard to flash");
            let mut serialized_card: [u8; RawCard::SERIALIZED_SIZE] = [0; RawCard::SERIALIZED_SIZE];
            raw_card.binary_serialize(&mut serialized_card, Endianness::Little);
            self.store.write(
                CARDS_REGION.offset + entry.offset * RawCard::SERIALIZED_SIZE as u32,
                &mut serialized_card,
            )?;
        } else {
            entry.last_read_date = timestamp;
            entry.read_count += 1;
        }

        entry.deleted = false;

        log::debug!("writing AllocationTableEntry to flash");
        let mut serialized_entry: [u8; AllocationTableEntry::SERIALIZED_SIZE] =
            [0; AllocationTableEntry::SERIALIZED_SIZE];
        entry.binary_serialize(&mut serialized_entry, Endianness::Little);
        self.store.write(
            ALLOCATION_TABLE_REGION.offset
                + entry.offset * AllocationTableEntry::SERIALIZED_SIZE as u32,
            &mut serialized_entry,
        )?;

        self.count += 1;
        log::debug!("writing card count to flash");
        let mut serialized_count: [u8; 4] = self.count.to_le_bytes();
        self.store
            .write(COUNT_REGION.offset, serialized_count.as_mut_slice())?;
        Ok(())
    }
}