#![no_main]

use arbitrary::Arbitrary;
use commonware_cryptography::{sha256::Digest, Hasher, Sha256};
use commonware_runtime::{buffer::paged::CacheRef, deterministic, Runner};
use commonware_storage::{
    mmr::Location,
    qmdb::{
        current::{unordered::fixed::Db as CurrentDb, FixedConfig as Config},
        store::LogStore as _,
    },
    translator::TwoCap,
};
use commonware_utils::{sequence::FixedBytes, NZUsize, NZU16, NZU64};
use libfuzzer_sys::fuzz_target;
use std::{
    collections::HashMap,
    num::{NonZeroU16, NonZeroU64},
};

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

#[derive(Arbitrary, Debug, Clone)]
enum CurrentOperation {
    Update {
        key: RawKey,
        value: RawValue,
    },
    Delete {
        key: RawKey,
    },
    Get {
        key: RawKey,
    },
    Commit,
    Prune,
    OpCount,
    Root,
    RangeProof {
        start_loc: u64,
        max_ops: NonZeroU64,
    },
    KeyValueProof {
        key: RawKey,
    },
    ArbitraryProof {
        start_loc: u64,
        bad_digests: Vec<[u8; 32]>,
        max_ops: NonZeroU64,
        bad_chunks: Vec<[u8; 32]>,
    },
}

const MAX_OPERATIONS: usize = 100;

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

impl<'a> Arbitrary<'a> for FuzzInput {
    fn arbitrary(u: &mut arbitrary::Unstructured<'a>) -> arbitrary::Result<Self> {
        let num_ops = u.int_in_range(1..=MAX_OPERATIONS)?;
        let operations = (0..num_ops)
            .map(|_| CurrentOperation::arbitrary(u))
            .collect::<Result<Vec<_>, _>>()?;
        Ok(FuzzInput { operations })
    }
}

const PAGE_SIZE: NonZeroU16 = NZU16!(88);
const PAGE_CACHE_SIZE: usize = 8;
const MMR_ITEMS_PER_BLOB: u64 = 11;
const LOG_ITEMS_PER_BLOB: u64 = 7;
const WRITE_BUFFER_SIZE: usize = 1024;

async fn commit_pending(
    db: &mut Db,
    pending_writes: &mut Vec<(Key, Option<Value>)>,
    committed_state: &mut HashMap<RawKey, Option<RawValue>>,
    pending_expected: &mut HashMap<RawKey, Option<RawValue>>,
) {
    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");
    committed_state.extend(pending_expected.drain());
}

fn fuzz(data: FuzzInput) {
    let runner = deterministic::Runner::default();

    runner.start(|context| async move {
        let mut hasher = Sha256::new();
        let cfg = Config {
            mmr_journal_partition: "fuzz-current-mmr-journal".into(),
            mmr_metadata_partition: "fuzz-current-mmr-metadata".into(),
            mmr_items_per_blob: NZU64!(MMR_ITEMS_PER_BLOB),
            mmr_write_buffer: NZUsize!(WRITE_BUFFER_SIZE),
            log_journal_partition: "fuzz-current-log-journal".into(),
            log_items_per_blob: NZU64!(LOG_ITEMS_PER_BLOB),
            log_write_buffer: NZUsize!(WRITE_BUFFER_SIZE),
            grafted_mmr_metadata_partition: "fuzz-current-grafted-mmr-metadata".into(),
            translator: TwoCap,
            page_cache: CacheRef::from_pooler(
                &context,
                PAGE_SIZE,
                NZUsize!(PAGE_CACHE_SIZE),
            ),
            thread_pool: None,
        };

        let mut db = Db::init(context.clone(), cfg)
            .await
            .expect("Failed to initialize Current database");

        // committed_state tracks state after apply_batch. pending_expected tracks
        // uncommitted mutations that haven't been applied yet.
        let mut committed_state: HashMap<RawKey, Option<RawValue>> = HashMap::new();
        let mut pending_expected: HashMap<RawKey, Option<RawValue>> = HashMap::new();
        let mut all_keys = std::collections::HashSet::new();
        let mut pending_writes: Vec<(Key, Option<Value>)> = Vec::new();
        let mut committed_op_count = Location::new(1);

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

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

                CurrentOperation::Delete { key } => {
                    let k = Key::new(*key);
                    // Check if key exists in committed state or pending writes.
                    let key_existed = db.get(&k).await.expect("Get before delete should not fail").is_some()
                        || pending_expected.get(key).is_some_and(|v| v.is_some());
                    if key_existed {
                        pending_writes.push((k, None));
                        pending_expected.insert(*key, None);
                        all_keys.insert(*key);
                    }
                }

                CurrentOperation::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(Some(expected_value)) => {
                            assert!(result.is_some(), "Expected value for key {key:?}");
                            let actual_value = result.expect("Should have value");
                            let actual_bytes: &[u8; 32] = actual_value.as_ref().try_into().expect("Value should be 32 bytes");
                            assert_eq!(actual_bytes, expected_value, "Value mismatch for key {key:?}");
                        }
                        Some(None) => {
                            assert!(result.is_none(), "Expected no value for deleted key {key:?}");
                        }
                        None => {
                            assert!(result.is_none(), "Expected no value for unset key {key:?}");
                        }
                    }

                    all_keys.insert(*key);
                }

                CurrentOperation::OpCount => {
                    let actual = db.bounds().await.end;
                    assert_eq!(
                        actual, committed_op_count,
                        "Op count mismatch: expected {committed_op_count}, got {actual}"
                    );
                }

                CurrentOperation::Commit => {
                    commit_pending(&mut db, &mut pending_writes, &mut committed_state, &mut pending_expected).await;
                    committed_op_count = db.bounds().await.end;
                }

                CurrentOperation::Prune => {
                    commit_pending(&mut db, &mut pending_writes, &mut committed_state, &mut pending_expected).await;
                    committed_op_count = db.bounds().await.end;
                    db.prune(db.inactivity_floor_loc()).await.expect("Prune should not fail");
                }

                CurrentOperation::Root => {
                    commit_pending(&mut db, &mut pending_writes, &mut committed_state, &mut pending_expected).await;
                    committed_op_count = db.bounds().await.end;
                    let _root = db.root();
                }

                CurrentOperation::RangeProof { start_loc, max_ops } => {
                    let current_op_count = db.bounds().await.end;
                    if current_op_count == 0 {
                        continue;
                    }

                    commit_pending(&mut db, &mut pending_writes, &mut committed_state, &mut pending_expected).await;
                    committed_op_count = db.bounds().await.end;
                    let current_root = db.root();

                    let current_op_count = db.bounds().await.end;
                    let start_loc = Location::new(start_loc % *current_op_count);
                    let oldest_loc = db.inactivity_floor_loc();
                    if start_loc >= oldest_loc {
                        let (proof, ops, chunks) = db
                            .range_proof(&mut hasher, start_loc, *max_ops)
                            .await
                            .expect("Range proof should not fail");

                        assert!(
                            Db::verify_range_proof(
                                &mut hasher,
                                &proof,
                                start_loc,
                                &ops,
                                &chunks,
                                &current_root
                                ),
                                "Range proof verification failed for start_loc={start_loc}, max_ops={max_ops}"
                            );
                    }
                }

                CurrentOperation::ArbitraryProof {start_loc, bad_digests, max_ops, bad_chunks} => {
                    let current_op_count = db.bounds().await.end;
                    if current_op_count == 0 {
                        continue;
                    }
                    commit_pending(&mut db, &mut pending_writes, &mut committed_state, &mut pending_expected).await;
                    committed_op_count = db.bounds().await.end;

                    let current_op_count = db.bounds().await.end;
                    let start_loc = Location::new(start_loc % current_op_count.as_u64());
                    let root = db.root();

                    if let Ok((range_proof, ops, chunks)) = db
                        .range_proof(&mut hasher, start_loc, *max_ops)
                        .await {
                        // Try to verify the proof when providing bad proof digests.
                        let bad_digests = bad_digests.iter().map(|d| Digest::from(*d)).collect();
                        if range_proof.proof.digests != bad_digests {
                            let mut bad_proof = range_proof.clone();
                            bad_proof.proof.digests = bad_digests;
                            assert!(!Db::verify_range_proof(
                                &mut hasher,
                                &bad_proof,
                                start_loc,
                                &ops,
                                &chunks,
                                &root
                            ), "proof with bad digests should not verify");
                        }

                        // Try to verify the proof when providing bad input chunks.
                        if &chunks != bad_chunks {
                            assert!(!Db::verify_range_proof(
                                &mut hasher,
                                &range_proof,
                                start_loc,
                                &ops,
                                bad_chunks,
                                &root
                            ), "proof with bad chunks should not verify");
                        }
                    }
                }

                CurrentOperation::KeyValueProof { key } => {
                    let k = Key::new(*key);

                    commit_pending(&mut db, &mut pending_writes, &mut committed_state, &mut pending_expected).await;
                    committed_op_count = db.bounds().await.end;
                    let current_root = db.root();

                    match db.key_value_proof(&mut hasher, k.clone()).await {
                        Ok(proof) => {
                            let value = db.get(&k).await.expect("get should not fail").expect("key should exist");
                            let verification_result = Db::verify_key_value_proof(
                                &mut hasher,
                                k,
                                value,
                                &proof,
                                &current_root,
                            );
                            assert!(verification_result, "Key value proof verification failed for key {key:?}");
                        }
                        Err(commonware_storage::qmdb::Error::KeyNotFound) => {
                            let expected_value = committed_state.get(key);
                            if let Some(Some(_)) = expected_value {
                                panic!("Key {key:?} should exist but proof generation failed");
                            }
                        }
                        Err(e) => {
                            panic!("Unexpected error during key value proof generation: {e:?}");
                        }
                    }
                }
            }
        }

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


        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(Some(expected_value)) => {
                    assert!(result.is_some(), "Lost value for key {key:?} at end");
                    let actual_value = result.expect("Should have value");
                    let actual_bytes: &[u8; 32] = actual_value.as_ref().try_into().expect("Value should be 32 bytes");
                    assert_eq!(actual_bytes, expected_value, "Final value mismatch for key {key:?}");
                }
                Some(None) => {
                    assert!(result.is_none(), "Deleted key {key:?} should remain deleted");
                }
                None => {
                    assert!(result.is_none(), "Unset key {key:?} should not exist");
                }
            }
        }

        db.destroy().await.expect("destroy should not fail");
    });
}

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