use axum::{
    extract::{Query, RawQuery, State},
    http::StatusCode,
    response::{IntoResponse, Response},
};
use cid::Cid;
use jacquard_repo::storage::BlockStore;
use serde::Deserialize;
use std::str::FromStr;
use tracing::error;
use tranquil_pds::api::error::ApiError;
use tranquil_pds::scheduled::generate_repo_car_from_user_blocks;
use tranquil_pds::state::AppState;
use tranquil_pds::sync::car::{encode_car_block, encode_car_header};
use tranquil_pds::sync::util::{RepoAccessLevel, assert_repo_availability};
use tranquil_types::Did;

struct GetBlocksParams {
    did: Did,
    cids: Vec<String>,
}

fn parse_get_blocks_query(query_string: &str) -> Result<GetBlocksParams, ApiError> {
    let did_str = tranquil_pds::util::parse_repeated_query_param(Some(query_string), "did")
        .into_iter()
        .next()
        .ok_or_else(|| ApiError::InvalidRequest("Missing required parameter: did".into()))?;
    let did: Did = did_str
        .parse()
        .map_err(|_| ApiError::InvalidRequest("invalid did".into()))?;
    let cids = tranquil_pds::util::parse_repeated_query_param(Some(query_string), "cids");
    Ok(GetBlocksParams { did, cids })
}

pub async fn get_blocks(State(state): State<AppState>, RawQuery(query): RawQuery) -> Response {
    let Some(query_string) = query else {
        return ApiError::InvalidRequest("Missing query parameters".into()).into_response();
    };

    let GetBlocksParams {
        did,
        cids: cid_strings,
    } = match parse_get_blocks_query(&query_string) {
        Ok(parsed) => parsed,
        Err(e) => return e.into_response(),
    };

    let _account =
        match assert_repo_availability(state.repos.repo.as_ref(), &did, RepoAccessLevel::Public)
            .await
        {
            Ok(a) => a,
            Err(e) => return e.into_response(),
        };

    let cids: Vec<Cid> = match cid_strings
        .iter()
        .map(|s| Cid::from_str(s).map_err(|_| s.clone()))
        .collect::<Result<Vec<_>, _>>()
    {
        Ok(cids) => cids,
        Err(invalid) => {
            return ApiError::InvalidRequest(format!("Invalid CID: {}", invalid)).into_response();
        }
    };

    if cids.is_empty() {
        return ApiError::InvalidRequest("No CIDs provided".into()).into_response();
    }

    let blocks = match state.block_store.get_many(&cids).await {
        Ok(blocks) => blocks,
        Err(e) => {
            error!("Failed to get blocks: {}", e);
            return ApiError::InternalError(None).into_response();
        }
    };

    let missing_cids: Vec<String> = blocks
        .iter()
        .zip(&cids)
        .filter(|(block_opt, _)| block_opt.is_none())
        .map(|(_, cid)| cid.to_string())
        .collect();
    if !missing_cids.is_empty() {
        return ApiError::InvalidRequest(format!(
            "Could not find blocks: {}",
            missing_cids.join(", ")
        ))
        .into_response();
    }

    let header = match tranquil_pds::sync::car::encode_car_header_null_root() {
        Ok(h) => h,
        Err(e) => {
            error!("Failed to encode CAR header: {}", e);
            return ApiError::InternalError(None).into_response();
        }
    };
    let mut car_bytes = header;
    blocks
        .into_iter()
        .enumerate()
        .filter_map(|(i, block_opt)| block_opt.map(|block| (cids[i], block)))
        .for_each(|(cid, block)| car_bytes.extend_from_slice(&encode_car_block(&cid, &block)));
    (
        StatusCode::OK,
        [(axum::http::header::CONTENT_TYPE, "application/vnd.ipld.car")],
        car_bytes,
    )
        .into_response()
}

#[derive(Deserialize)]
pub struct GetRepoQuery {
    pub did: Did,
    pub since: Option<String>,
}

pub async fn get_repo(
    State(state): State<AppState>,
    Query(query): Query<GetRepoQuery>,
) -> Response {
    let did = query.did;
    let account =
        match assert_repo_availability(state.repos.repo.as_ref(), &did, RepoAccessLevel::Public)
            .await
        {
            Ok(a) => a,
            Err(e) => return e.into_response(),
        };

    let Some(head_str) = account.repo_root_cid else {
        return ApiError::RepoNotFound(Some("Repo not initialized".into())).into_response();
    };

    let Ok(head_cid) = Cid::from_str(&head_str) else {
        return ApiError::InternalError(None).into_response();
    };

    if let Some(since) = &query.since {
        return get_repo_since(&state, &did, &head_cid, since).await;
    }

    let _permit = match state.repo_export_semaphore.try_acquire() {
        Ok(permit) => permit,
        Err(_) => {
            return (
                StatusCode::SERVICE_UNAVAILABLE,
                "Too many concurrent repo exports",
            )
                .into_response();
        }
    };

    let car_bytes = match generate_repo_car_from_user_blocks(
        state.repos.repo.as_ref(),
        &state.block_store,
        account.user_id,
        &head_cid,
    )
    .await
    {
        Ok(bytes) => bytes,
        Err(e) => {
            error!("Failed to generate repo CAR: {}", e);
            return ApiError::InternalError(None).into_response();
        }
    };

    (
        StatusCode::OK,
        [(axum::http::header::CONTENT_TYPE, "application/vnd.ipld.car")],
        car_bytes,
    )
        .into_response()
}

async fn get_repo_since(state: &AppState, did: &Did, head_cid: &Cid, since: &str) -> Response {
    let user_id = match state.repos.user.get_id_by_did(did).await {
        Ok(Some(id)) => id,
        Ok(None) => {
            return ApiError::RepoNotFound(Some(format!("Could not find repo for DID: {}", did)))
                .into_response();
        }
        Err(e) => {
            error!("DB error looking up user: {:?}", e);
            return ApiError::InternalError(Some("Database error".into())).into_response();
        }
    };

    let block_cid_bytes = match state
        .repos
        .repo
        .get_user_block_cids_since_rev(user_id, since)
        .await
    {
        Ok(cids) => cids,
        Err(e) => {
            error!("DB error in get_repo_since: {:?}", e);
            return ApiError::InternalError(Some("Database error".into())).into_response();
        }
    };

    let block_cids: Vec<Cid> = block_cid_bytes
        .iter()
        .filter_map(|bytes| Cid::try_from(bytes.as_slice()).ok())
        .collect();

    let mut car_bytes = match encode_car_header(head_cid) {
        Ok(h) => h,
        Err(e) => {
            return ApiError::InternalError(Some(format!("Failed to encode CAR header: {}", e)))
                .into_response();
        }
    };

    if block_cids.is_empty() {
        return (
            StatusCode::OK,
            [(axum::http::header::CONTENT_TYPE, "application/vnd.ipld.car")],
            car_bytes,
        )
            .into_response();
    }

    for chunk_start in (0..block_cids.len()).step_by(500) {
        let chunk_end = (chunk_start + 500).min(block_cids.len());
        let chunk = &block_cids[chunk_start..chunk_end];
        let blocks = match state.block_store.get_many(chunk).await {
            Ok(b) => b,
            Err(e) => {
                error!("Block store error in get_repo_since: {:?}", e);
                return ApiError::InternalError(Some("Failed to get blocks".into()))
                    .into_response();
            }
        };

        chunk
            .iter()
            .zip(blocks)
            .filter_map(|(cid, block_opt)| block_opt.map(|block| (*cid, block)))
            .for_each(|(cid, block)| car_bytes.extend_from_slice(&encode_car_block(&cid, &block)));
    }

    (
        StatusCode::OK,
        [(axum::http::header::CONTENT_TYPE, "application/vnd.ipld.car")],
        car_bytes,
    )
        .into_response()
}

#[derive(Deserialize)]
pub struct GetRecordQuery {
    pub did: Did,
    pub collection: String,
    pub rkey: String,
}

pub async fn get_record(
    State(state): State<AppState>,
    Query(query): Query<GetRecordQuery>,
) -> Response {
    use jacquard_repo::commit::Commit;
    use jacquard_repo::mst::Mst;
    use std::collections::BTreeMap;
    use std::sync::Arc;

    let did = query.did;
    let account =
        match assert_repo_availability(state.repos.repo.as_ref(), &did, RepoAccessLevel::Public)
            .await
        {
            Ok(a) => a,
            Err(e) => return e.into_response(),
        };

    let commit_cid_str = match account.repo_root_cid {
        Some(cid) => cid,
        None => {
            return ApiError::RepoNotFound(Some("Repo not initialized".into())).into_response();
        }
    };
    let Ok(commit_cid) = Cid::from_str(&commit_cid_str) else {
        return ApiError::InternalError(Some("Invalid commit CID".into())).into_response();
    };
    let commit_bytes = match state.block_store.get(&commit_cid).await {
        Ok(Some(b)) => b,
        _ => {
            return ApiError::InternalError(Some("Commit block not found".into())).into_response();
        }
    };
    let Ok(commit) = Commit::from_cbor(&commit_bytes) else {
        return ApiError::InternalError(Some("Failed to parse commit".into())).into_response();
    };
    let mst = Mst::load(Arc::new(state.block_store.clone()), commit.data, None);
    let key = format!("{}/{}", query.collection, query.rkey);
    let record_cid = match mst.get(&key).await {
        Ok(Some(cid)) => cid,
        Ok(None) => {
            return ApiError::RecordNotFound.into_response();
        }
        Err(_) => {
            return ApiError::InternalError(Some("Failed to lookup record".into())).into_response();
        }
    };
    let record_block = match state.block_store.get(&record_cid).await {
        Ok(Some(b)) => b,
        _ => {
            return ApiError::RecordNotFound.into_response();
        }
    };
    let mut proof_blocks: BTreeMap<Cid, bytes::Bytes> = BTreeMap::new();
    if mst.blocks_for_path(&key, &mut proof_blocks).await.is_err() {
        return ApiError::InternalError(Some("Failed to build proof path".into())).into_response();
    }
    let header = match encode_car_header(&commit_cid) {
        Ok(h) => h,
        Err(e) => {
            error!("Failed to encode CAR header: {}", e);
            return ApiError::InternalError(None).into_response();
        }
    };
    let mut car_bytes = header;
    car_bytes.extend_from_slice(&encode_car_block(&commit_cid, &commit_bytes));
    proof_blocks
        .iter()
        .for_each(|(cid, data)| car_bytes.extend_from_slice(&encode_car_block(cid, data)));
    car_bytes.extend_from_slice(&encode_car_block(&record_cid, &record_block));
    (
        StatusCode::OK,
        [(axum::http::header::CONTENT_TYPE, "application/vnd.ipld.car")],
        car_bytes,
    )
        .into_response()
}
