#![no_main]

use arbitrary::Arbitrary;
use commonware_cryptography::{sha256::Digest, Sha256};
use commonware_runtime::{buffer::paged::CacheRef, deterministic, Runner};
use commonware_storage::{
    mmr::{Location, Proof, StandardHasher as Standard},
    qmdb::{
        any::{ordered::fixed::Db as AnyDb, FixedConfig as Config},
        store::LogStore as _,
        verify_proof,
    },
    translator::EightCap,
};
use commonware_utils::{sequence::FixedBytes, NZUsize, NZU16, NZU64};
use libfuzzer_sys::fuzz_target;
use std::{
    collections::{HashMap, HashSet},
    num::{NonZeroU16, NonZeroU64},
};

type Key = FixedBytes<32>;
type Value = FixedBytes<64>;
type RawKey = [u8; 32];
type RawValue = [u8; 64];
type Db = AnyDb<deterministic::Context, Key, Value, Sha256, EightCap>;

const MAX_OPS: usize = 25;

#[derive(Arbitrary, Debug, Clone)]
enum QmdbOperation {
    Update {
        key: RawKey,
        value: RawValue,
    },
    Delete {
        key: RawKey,
    },
    Commit,
    OpCount,
    Root,
    Proof {
        start_loc: u64,
        max_ops: NonZeroU64,
    },
    ArbitraryProof {
        start_loc: u64,
        max_ops: NonZeroU64,
        proof_leaves: Location,
        digests: Vec<[u8; 32]>,
    },
    Get {
        key: RawKey,
    },
    GetSpan {
        key: RawKey,
    },
}

#[derive(Arbitrary, Debug)]
struct FuzzInput {
    operations: Vec<QmdbOperation>,
}

const PAGE_SIZE: NonZeroU16 = NZU16!(555);
const PAGE_CACHE_SIZE: usize = 100;

async fn commit_pending(
    db: &mut Db,
    pending_writes: &mut Vec<(Key, Option<Value>)>,
    committed_state: &mut HashMap<RawKey, RawValue>,
    pending_inserts: &mut HashMap<RawKey, RawValue>,
    pending_deletes: &mut HashSet<RawKey>,
) {
    let finalized = {
        let mut batch = db.new_batch();
        for (k, v) in pending_writes.drain(..) {
            batch.write(k, v);
        }
        batch.merkleize(None).await.unwrap().finalize()
    };
    db.apply_batch(finalized)
        .await
        .expect("commit should not fail");
    for key in pending_deletes.drain() {
        committed_state.remove(&key);
    }
    committed_state.extend(pending_inserts.drain());
}

fn fuzz(data: FuzzInput) {
    let mut hasher = Standard::<Sha256>::new();
    let runner = deterministic::Runner::default();

    runner.start(|context| async move {
        let cfg = Config::<EightCap> {
            mmr_journal_partition: "test-qmdb-mmr-journal".into(),
            mmr_items_per_blob: NZU64!(500000),
            mmr_write_buffer: NZUsize!(1024),
            mmr_metadata_partition: "test-qmdb-mmr-metadata".into(),
            log_journal_partition: "test-qmdb-log-journal".into(),
            log_items_per_blob: NZU64!(500000),
            log_write_buffer: NZUsize!(1024),
            translator: EightCap,
            thread_pool: None,
            page_cache: CacheRef::from_pooler(
                &context,
                PAGE_SIZE,
                NZUsize!(PAGE_CACHE_SIZE),
            ),
        };

        let mut db = Db::init(context.clone(), cfg.clone())
            .await
            .expect("init qmdb");

        // committed_state tracks state after apply_batch. pending_expected tracks
        // uncommitted mutations that haven't been applied yet.
        let mut committed_state: HashMap<RawKey, RawValue> = HashMap::new();
        let mut pending_inserts: HashMap<RawKey, RawValue> = HashMap::new();
        let mut pending_deletes: HashSet<RawKey> = HashSet::new();
        let mut all_keys: HashSet<RawKey> = HashSet::new();
        let mut pending_writes: Vec<(Key, Option<Value>)> = Vec::new();

        for op in data.operations.iter().take(MAX_OPS) {
            match op {
                QmdbOperation::Update { key, value } => {
                    let k = Key::new(*key);
                    let v = Value::new(*value);

                    pending_writes.push((k, Some(v)));
                    pending_deletes.remove(key);
                    pending_inserts.insert(*key, *value);
                    all_keys.insert(*key);
                }

                QmdbOperation::Delete { key } => {
                    let k = Key::new(*key);
                    pending_writes.push((k, None));
                    pending_inserts.remove(key);
                    pending_deletes.insert(*key);
                }

                QmdbOperation::OpCount => {
                    let _ = db.bounds().await.end;
                }

                QmdbOperation::Commit => {
                    commit_pending(
                        &mut db, &mut pending_writes, &mut committed_state,
                        &mut pending_inserts, &mut pending_deletes,
                    ).await;
                }

                QmdbOperation::Root => {
                    commit_pending(
                        &mut db, &mut pending_writes, &mut committed_state,
                        &mut pending_inserts, &mut pending_deletes,
                    ).await;
                    db.root();
                }

                QmdbOperation::Proof { start_loc, max_ops } => {
                    commit_pending(
                        &mut db, &mut pending_writes, &mut committed_state,
                        &mut pending_inserts, &mut pending_deletes,
                    ).await;
                    let actual_op_count = db.bounds().await.end;

                    if actual_op_count > 0 {
                        let current_root = db.root();
                        let adjusted_start = Location::new(*start_loc % *actual_op_count);
                        let (proof, log) = db
                            .proof(adjusted_start, *max_ops)
                            .await
                            .expect("proof should not fail");

                        assert!(
                            verify_proof(
                                &mut hasher,
                                &proof,
                                adjusted_start,
                                &log,
                                &current_root
                            ),
                            "Proof verification failed for start_loc={adjusted_start}, max_ops={max_ops}",
                        );
                    }
                }

                QmdbOperation::ArbitraryProof { start_loc, max_ops , proof_leaves, digests} => {
                    commit_pending(
                        &mut db, &mut pending_writes, &mut committed_state,
                        &mut pending_inserts, &mut pending_deletes,
                    ).await;
                    let actual_op_count = db.bounds().await.end;

                    let proof = Proof {
                        leaves: *proof_leaves,
                        digests: digests.iter().map(|d| Digest::from(*d)).collect(),
                    };

                    if actual_op_count > 0 {
                        let current_root = db.root();
                        let adjusted_start = Location::new(*start_loc % *actual_op_count);

                        if let Ok(res) = db
                            .proof(adjusted_start, *max_ops)
                            .await {
                                let _ = verify_proof(
                                    &mut hasher,
                                    &proof,
                                    adjusted_start,
                                    &res.1,
                                    &current_root
                                );

                        }
                    }
                }

                QmdbOperation::Get { key } => {
                    let k = Key::new(*key);
                    let result = db.get(&k).await.expect("get should not fail");

                    // Verify against committed state only.
                    match committed_state.get(key) {
                        Some(expected_value) => {
                            let v = result.expect("get should not fail");
                            let v_bytes: &[u8; 64] = v.as_ref().try_into().expect("bytes");
                            assert_eq!(v_bytes, expected_value, "Value mismatch for key {key:?}");
                        }
                        None => {
                            assert!(
                                result.is_none(),
                                "Found unexpected value for key {key:?} that was never touched",
                            );
                        }
                    }
                    all_keys.insert(*key);
                }

                QmdbOperation::GetSpan { key } => {
                    let k = Key::new(*key);
                    let result = db.get_span(&k).await.expect("get should not fail");
                    assert_eq!(result.is_some(), !db.is_empty(), "span should be empty only if db is empty");
                }
            }
        }

        // Final commit to ensure all operations are persisted.
        if !pending_writes.is_empty() {
            commit_pending(
                &mut db, &mut pending_writes, &mut committed_state,
                &mut pending_inserts, &mut pending_deletes,
            ).await;
        }

        // Comprehensive final verification - check ALL keys ever touched.
        for key in &all_keys {
            let k = Key::new(*key);
            let result = db.get(&k).await.expect("final get should not fail");

            match committed_state.get(key) {
                Some(expected_value) => {
                    let v = result.expect("get should not fail");
                    let v_bytes: &[u8; 64] = v.as_ref().try_into().expect("bytes");
                    assert_eq!(
                        v_bytes, expected_value,
                        "Final value mismatch for key {key:?}"
                    );
                }
                None => {
                    assert!(
                        result.is_none(),
                        "Deleted key {key:?} should remain deleted, but found value",
                    );
                },
            }
        }

        let finalized = db.new_batch().merkleize(None).await.unwrap().finalize();
        db.apply_batch(finalized).await.expect("final commit should not fail");
        db.destroy().await.expect("destroy should not fail");
    });
}

fuzz_target!(|input: FuzzInput| {
    fuzz(input);
});