host-chain-core 0.3.2

//! Async DOTNS (DOT Name Service) on-chain resolution.
//!
//! Resolves `.dot` domain names to IPFS content hashes by querying the
//! DOTNS content resolver contract on Asset Hub Paseo via `state_call`.
//! Uses `reqwest` for HTTP — same code on native (rustls-tls) and WASM
//! (browser fetch via web-sys).
//!
//! Flow:
//! 1. ENS-style namehash of the domain (keccak256)
//! 2. ABI-encode the `contenthash(bytes32)` call
//! 3. SCALE-encode `ReviveApi::call()` parameters
//! 4. Send `state_call("ReviveApi_call", params)` via JSON-RPC HTTP
//! 5. Decode the response to extract the IPFS CID
//! 6. Fetch the CID from the IPFS gateway as a CARv1 file
//! 7. Parse the CAR file into a flat filename → bytes map

use crate::car::{is_car_file, parse_car_to_assets};
use std::collections::{HashMap, HashSet};
use std::error::Error as _;
use std::sync::OnceLock;

fn shared_client() -> &'static reqwest::Client {
    static CLIENT: OnceLock<reqwest::Client> = OnceLock::new();
    CLIENT.get_or_init(|| {
        #[cfg(not(target_arch = "wasm32"))]
        {
            reqwest::Client::builder()
                .timeout(std::time::Duration::from_secs(30))
                .build()
                .expect("failed to build reqwest client")
        }
        #[cfg(target_arch = "wasm32")]
        {
            reqwest::Client::new()
        }
    })
}

// Pure encoding/decoding functions — delegated to host-encoding crate.
pub use host_encoding::dotns::{
    base32_encode, contenthash_to_cid, decode_abi_bytes, decode_contract_result,
    decode_scale_compact, decode_unsigned_varint, encode_contenthash_call, hex_addr, hex_decode,
    hex_encode, hex_nibble, keccak256, namehash, scale_compact_len, scale_compact_u64,
    scale_encode_revive_call,
};

/// DOTNS content resolver contract on Asset Hub Paseo.
pub const CONTENT_RESOLVER: [u8; 20] = hex_addr("7756DF72CBc7f062e7403cD59e45fBc78bed1cD7");

/// DOTNS registry contract on Asset Hub Paseo.
pub const REGISTRY: [u8; 20] = hex_addr("4Da0d37aBe96C06ab19963F31ca2DC0412057a6f");

/// Solidity function selector for `owner(bytes32)` on the DOTNS registry.
/// keccak256("owner(bytes32)")[:4]
pub const OWNER_SELECTOR: [u8; 4] = [0x02, 0x57, 0x1b, 0xe3];

/// JSON-RPC endpoints for Asset Hub Paseo (tried in order).
const RPC_ENDPOINTS: &[&str] = &[
    "https://sys.ibp.network/asset-hub-paseo",
    "https://asset-hub-paseo.dotters.network",
];

/// IPFS gateway for fetching resolved content.
pub const IPFS_GATEWAY: &str = "https://paseo-ipfs.polkadot.io";

/// The IPFS gateway URL used for fetching content.
pub fn ipfs_gateway() -> &'static str {
    IPFS_GATEWAY
}

/// Result of a full DOTNS resolution — includes the CID for verification display.
pub struct DotnsResolution {
    /// The IPFS CID that was resolved on-chain.
    pub cid: String,
    /// On-chain owner/addr associated with this name (if resolvable).
    pub owner: Option<String>,
    /// Fetched assets from IPFS.
    pub assets: HashMap<String, Vec<u8>>,
}

/// Send a `state_call` JSON-RPC request via HTTP (async, reqwest).
pub async fn rpc_state_call(method: &str, params_hex: &str) -> Result<Vec<u8>, String> {
    let payload = serde_json::json!({
        "jsonrpc": "2.0",
        "id": 1,
        "method": "state_call",
        "params": [method, params_hex]
    });
    let payload_str = payload.to_string();

    let client = shared_client();

    for endpoint in RPC_ENDPOINTS {
        log::info!("[dotns] trying RPC: {endpoint}");
        let result = client
            .post(*endpoint)
            .header("Content-Type", "application/json")
            .body(payload_str.clone())
            .send()
            .await;

        match result {
            Ok(resp) => {
                let resp_bytes = match resp.bytes().await {
                    Ok(b) => b,
                    Err(e) => {
                        log::warn!("[dotns] failed to read response from {endpoint}: {e}");
                        continue;
                    }
                };
                let body: serde_json::Value = match serde_json::from_slice(&resp_bytes) {
                    Ok(v) => v,
                    Err(e) => {
                        log::warn!("[dotns] failed to parse response from {endpoint}: {e}");
                        continue;
                    }
                };
                let body_str = body.to_string();
                log::debug!(
                    "[dotns] response: {}",
                    if body_str.len() > 200 {
                        &body_str[..200]
                    } else {
                        &body_str
                    }
                );
                if let Some(err) = body.get("error") {
                    log::warn!("[dotns] RPC error from {endpoint}: {err}");
                    continue;
                }
                if let Some(result) = body.get("result").and_then(|v| v.as_str()) {
                    return hex_decode(result)
                        .ok_or_else(|| format!("invalid hex in RPC response: {result}"));
                }
                log::warn!("[dotns] unexpected response from {endpoint}: {body}");
                continue;
            }
            Err(e) => {
                log::warn!("[dotns] HTTP error for {endpoint}: {e}");
                continue;
            }
        }
    }

    Err("all RPC endpoints failed".into())
}

/// Resolve a `.dot` domain name to an IPFS CID via DOTNS on-chain lookup (async).
///
/// Returns the CID string (e.g. "bafybeig...") or an error.
pub async fn resolve_dotns(name: &str) -> Result<String, String> {
    let domain = if name.ends_with(".dot") {
        name.to_string()
    } else {
        format!("{name}.dot")
    };

    log::info!("[dotns] resolving: {domain}");

    // 1. Compute namehash
    let node = namehash(&domain);
    log::info!("[dotns] namehash: {}", hex_encode(&node));

    // 2. ABI-encode contenthash(bytes32) call
    let call_data = encode_contenthash_call(&node);
    log::info!("[dotns] call_data encoded ({} bytes)", call_data.len());

    // 3. SCALE-encode ReviveApi::call() params
    let params = scale_encode_revive_call(&CONTENT_RESOLVER, &call_data)?;
    let params_hex = hex_encode(&params);
    log::info!(
        "[dotns] params encoded ({} hex chars), calling RPC...",
        params_hex.len()
    );

    // 4. RPC state_call
    let response = rpc_state_call("ReviveApi_call", &params_hex).await?;
    log::info!("[dotns] got response: {} bytes", response.len());

    // 5. Decode ContractResult → return data
    let return_data = decode_contract_result(&response)?;
    log::info!("[dotns] contract return data: {} bytes", return_data.len());

    if return_data.is_empty() {
        return Err("domain not registered (empty return data)".into());
    }

    // 6. Decode ABI-encoded bytes
    let contenthash = decode_abi_bytes(&return_data)?;
    log::info!("[dotns] contenthash: {} bytes", contenthash.len());

    if contenthash.is_empty() {
        return Err("domain has no contenthash set".into());
    }

    // 7. Parse contenthash → CID
    let cid = contenthash_to_cid(&contenthash)?;
    log::info!("[dotns] resolved CID: {cid}");

    Ok(cid)
}

/// Resolve the owner of a .dot name by calling `owner(bytes32)` on the DOTNS registry (async).
/// Returns the H160 address as a `0x`-prefixed hex string, or `None` on failure.
pub async fn resolve_owner(name: &str) -> Option<String> {
    let domain = if name.ends_with(".dot") {
        name.to_string()
    } else {
        format!("{name}.dot")
    };
    let node = namehash(&domain);

    let mut call_data = Vec::with_capacity(36);
    call_data.extend_from_slice(&OWNER_SELECTOR);
    call_data.extend_from_slice(&node);

    let params = scale_encode_revive_call(&REGISTRY, &call_data).ok()?;
    let params_hex = hex_encode(&params);

    let response = rpc_state_call("ReviveApi_call", &params_hex).await.ok()?;
    let return_data = decode_contract_result(&response).ok()?;

    // ABI-encoded address: 32 bytes, address right-aligned (bytes 12..32).
    if return_data.len() < 32 {
        return None;
    }
    let addr_bytes = &return_data[12..32];
    if addr_bytes.iter().all(|&b| b == 0) {
        return None;
    }
    Some(format!(
        "0x{}",
        addr_bytes
            .iter()
            .map(|b| format!("{b:02x}"))
            .collect::<String>()
    ))
}

/// Fetch an IPFS URL with a configurable byte limit (async, reqwest).
pub async fn fetch_ipfs_url_with_limit(
    url: &str,
    max_bytes: usize,
) -> Result<(String, Vec<u8>), String> {
    #[allow(unused_mut)]
    let mut resp = shared_client().get(url).send().await.map_err(|e| {
        let mut msg = format!("IPFS fetch failed: {e}");
        let mut source: Option<&dyn std::error::Error> = e.source();
        while let Some(cause) = source {
            msg.push_str(&format!(" → {cause}"));
            source = cause.source();
        }
        msg
    })?;

    let content_type = resp
        .headers()
        .get("Content-Type")
        .and_then(|v| v.to_str().ok())
        .unwrap_or("")
        .to_string();

    // Early rejection based on Content-Length header.
    if let Some(cl) = resp.content_length() {
        if cl > max_bytes as u64 {
            return Err(format!(
                "IPFS response too large: Content-Length {cl} > {max_bytes}"
            ));
        }
    }

    // Read the body, enforcing the size limit.
    // On native, use chunk() for streaming; on WASM, use bytes() (no streaming API).
    #[cfg(not(target_arch = "wasm32"))]
    let bytes = {
        let mut buf = Vec::new();
        while let Some(chunk) = resp
            .chunk()
            .await
            .map_err(|e| format!("IPFS read failed: {e}"))?
        {
            buf.extend_from_slice(&chunk);
            if buf.len() > max_bytes {
                return Err(format!(
                    "IPFS response too large: {} > {max_bytes}",
                    buf.len()
                ));
            }
        }
        buf
    };
    #[cfg(target_arch = "wasm32")]
    let bytes = {
        let buf = resp
            .bytes()
            .await
            .map_err(|e| format!("IPFS read failed: {e}"))?;
        if buf.len() > max_bytes {
            return Err(format!(
                "IPFS response too large: {} > {max_bytes}",
                buf.len()
            ));
        }
        buf.to_vec()
    };

    Ok((content_type, bytes))
}

async fn fetch_ipfs_url(url: &str) -> Result<(String, Vec<u8>), String> {
    fetch_ipfs_url_with_limit(url, 10 * 1024 * 1024).await
}

async fn fetch_ipfs_url_large(url: &str) -> Result<(String, Vec<u8>), String> {
    fetch_ipfs_url_with_limit(url, 64 * 1024 * 1024).await
}

fn looks_like_directory_listing(body: &[u8]) -> bool {
    let s = std::str::from_utf8(body).unwrap_or("");
    s.contains("Index of /ipfs")
        || s.contains("<title>Index of")
        || (s.contains("Index of") && s.contains("/ipfs/"))
}

/// Fetch content from IPFS and return a map of filename → bytes (async).
///
/// Strategy:
/// 1. Request the entire directory tree as a CARv1 file via `?format=car`.
///    Single round-trip; the parser handles both standard UnixFS and
///    zstd-compressed leaves.
/// 2. Request directory listing via `Accept: text/html` + `?format=html` query
///    param (forces gateway to return listing instead of index.html).
/// 3. If that works, parse filenames from listing and fetch each file.
/// 4. If the CID is a single file (not a directory), treat it as index.html.
pub async fn fetch_ipfs(cid: &str) -> Result<HashMap<String, Vec<u8>>, String> {
    log::info!("[dotns] fetching IPFS: {cid}");

    // Try CAR format first — single roundtrip, returns entire directory tree.
    let car_url = format!("{IPFS_GATEWAY}/ipfs/{cid}?format=car");
    if let Ok((ct, body)) = fetch_ipfs_url_large(&car_url).await {
        if ct.contains("vnd.ipld.car") || is_car_file(&body) {
            log::info!(
                "[dotns] got CAR response ({} bytes), parsing...",
                body.len()
            );
            return parse_car_to_assets(&body);
        }
    }

    // Try to get a directory listing.
    let listing_url = format!("{IPFS_GATEWAY}/ipfs/{cid}/?format=html&noResolve");
    if let Ok((ct, body)) = fetch_ipfs_url(&listing_url).await {
        if ct.contains("text/html") && looks_like_directory_listing(&body) {
            log::info!("[dotns] got directory listing for {cid}");
            return fetch_ipfs_directory(cid, &body).await;
        }
    }

    // Fallback: try trailing-slash request.
    let dir_url = format!("{IPFS_GATEWAY}/ipfs/{cid}/");
    if let Ok((content_type, body)) = fetch_ipfs_url_large(&dir_url).await {
        if content_type.contains("octet-stream") && body.len() > 60 && is_car_file(&body) {
            log::info!(
                "[dotns] detected CAR file from dir request ({} bytes)",
                body.len()
            );
            return parse_car_to_assets(&body);
        }
        if content_type.contains("text/html") && looks_like_directory_listing(&body) {
            return fetch_ipfs_directory(cid, &body).await;
        }
        // Gateway served index.html directly — parse HTML for referenced local assets.
        let mut assets = HashMap::new();
        let referenced = extract_local_references(&body);
        let futs: Vec<_> = referenced
            .iter()
            .map(|path| {
                let url = format!("{IPFS_GATEWAY}/ipfs/{cid}/{path}");
                let path = path.clone();
                async move {
                    log::info!("[dotns] fetching referenced asset: {path}");
                    fetch_ipfs_url(&url).await.map(|(_, b)| (path, b))
                }
            })
            .collect();
        let results = futures::future::join_all(futs).await;
        for result in results {
            match result {
                Ok((path, file_body)) => {
                    assets.insert(path, file_body);
                }
                Err(e) => {
                    log::warn!("[dotns] failed to fetch asset: {e}");
                }
            }
        }
        assets.insert("index.html".into(), body);
        return Ok(assets);
    }

    // Last resort: fetch without trailing slash — might be a single file or CAR.
    let url = format!("{IPFS_GATEWAY}/ipfs/{cid}");
    let (content_type, body) = fetch_ipfs_url_large(&url).await?;

    if content_type.contains("octet-stream") && body.len() > 60 && is_car_file(&body) {
        log::info!(
            "[dotns] detected CAR file ({} bytes), parsing...",
            body.len()
        );
        return parse_car_to_assets(&body);
    }

    let mut assets = HashMap::new();
    assets.insert("index.html".into(), body);
    Ok(assets)
}

/// Extract local asset paths referenced in HTML (src="...", href="...").
fn extract_local_references(html_bytes: &[u8]) -> Vec<String> {
    let html = std::str::from_utf8(html_bytes).unwrap_or("");
    let mut paths: Vec<String> = Vec::new();
    let mut seen: HashSet<String> = HashSet::new();
    for attr in &["src=\"", "href=\""] {
        for segment in html.split(attr).skip(1) {
            if let Some(end) = segment.find('"') {
                let path = &segment[..end];
                if path.is_empty()
                    || path.starts_with("http://")
                    || path.starts_with("https://")
                    || path.starts_with("//")
                    || path.starts_with("data:")
                    || path.starts_with('#')
                    || path.starts_with("javascript:")
                {
                    continue;
                }
                let clean = path.trim_start_matches("./");
                if !clean.is_empty() && !clean.contains("..") && seen.insert(clean.to_string()) {
                    paths.push(clean.to_string());
                }
            }
        }
    }
    paths
}

async fn fetch_ipfs_directory(
    cid: &str,
    listing_html: &[u8],
) -> Result<HashMap<String, Vec<u8>>, String> {
    let mut assets = HashMap::new();
    fetch_ipfs_directory_recursive(cid, "", listing_html, &mut assets, 0).await?;
    if assets.is_empty() {
        return Err("directory listing contained no files".into());
    }
    Ok(assets)
}

/// Recursively fetch IPFS directory contents, using `futures::future::join_all`
/// for parallel file fetches (replaces `std::thread::scope`).
// Note: this function is async and recursive. On WASM there is no thread::spawn,
// but async recursion works fine. We use Box::pin to satisfy the type checker for
// indirect recursion (async fn → BoxFuture).
// The future is NOT marked Send because reqwest's WASM backend uses Rc internally.
fn fetch_ipfs_directory_recursive<'a>(
    cid: &'a str,
    prefix: &'a str,
    listing_html: &'a [u8],
    assets: &'a mut HashMap<String, Vec<u8>>,
    depth: u8,
) -> std::pin::Pin<Box<dyn std::future::Future<Output = Result<(), String>> + 'a>> {
    Box::pin(async move {
        if depth > 8 {
            log::warn!("[dotns] recursion depth limit reached at prefix={prefix}");
            return Ok(());
        }
        let html = std::str::from_utf8(listing_html).map_err(|e| format!("invalid UTF-8: {e}"))?;

        let cid_prefix = format!("/ipfs/{cid}/");
        let mut seen_names: HashSet<String> = HashSet::new();
        let mut names: Vec<String> = Vec::new();
        for segment in html.split("<a href=\"") {
            if let Some(end) = segment.find('"') {
                let href = &segment[..end];
                if let Some(name) = href.strip_prefix(&cid_prefix) {
                    let clean = name.trim_end_matches('/');
                    if !clean.is_empty()
                        && !clean.contains('/')
                        && !clean.contains("..")
                        && seen_names.insert(clean.to_string())
                    {
                        names.push(clean.to_string());
                    }
                }
            }
        }

        // Separate subdirectories (must be handled sequentially to mutably borrow assets)
        // from plain files (fetched in parallel).
        let mut file_entries: Vec<(String, String)> = Vec::new(); // (path, url)

        for name in &names {
            let path = if prefix.is_empty() {
                name.clone()
            } else {
                format!("{prefix}/{name}")
            };

            let sub_cid = extract_sub_cid(html, name);
            if let Some(ref sc) = sub_cid {
                let dir_url = format!("{IPFS_GATEWAY}/ipfs/{sc}/?format=html&noResolve");
                match fetch_ipfs_url(&dir_url).await {
                    Ok((_, body)) => {
                        if looks_like_directory_listing(&body) {
                            log::info!("[dotns] recursing into subdirectory: {path}");
                            fetch_ipfs_directory_recursive(sc, &path, &body, assets, depth + 1)
                                .await?;
                            continue;
                        }
                    }
                    Err(e) => {
                        log::warn!("[dotns] failed to list subdir {path}: {e}");
                    }
                }
            }

            let url = format!("{IPFS_GATEWAY}/ipfs/{cid}/{name}");
            file_entries.push((path, url));
        }

        // Fetch plain files concurrently (join_all, bounded by browser / tokio scheduler).
        const BATCH_SIZE: usize = 6;
        for chunk in file_entries.chunks(BATCH_SIZE) {
            let futs: Vec<_> = chunk
                .iter()
                .map(|(path, url)| {
                    let path = path.clone();
                    let url = url.clone();
                    async move {
                        log::info!("[dotns] fetching: {path}");
                        fetch_ipfs_url_large(&url)
                            .await
                            .map(|(_, body)| (path, body))
                    }
                })
                .collect();
            let results = futures::future::join_all(futs).await;
            for result in results {
                match result {
                    Ok((path, body)) => {
                        assets.insert(path, body);
                    }
                    Err(e) => {
                        log::warn!("[dotns] failed to fetch file: {e}");
                    }
                }
            }
        }

        Ok(())
    })
}

/// Extract the CID for a subdirectory from the directory listing HTML.
fn extract_sub_cid(html: &str, name: &str) -> Option<String> {
    let needle = format!("?filename={name}");
    for segment in html.split("href=\"") {
        if let Some(end) = segment.find('"') {
            let href = &segment[..end];
            if href.ends_with(&needle) {
                let without_query = href.strip_suffix(&needle)?;
                let sub_cid = without_query.strip_prefix("/ipfs/")?;
                return Some(sub_cid.to_string());
            }
        }
    }
    None
}

/// Full resolution pipeline: DOTNS lookup → IPFS fetch → asset map (async).
pub async fn resolve_and_fetch(name: &str) -> Result<HashMap<String, Vec<u8>>, String> {
    let r = resolve_and_fetch_full(name).await?;
    Ok(r.assets)
}

/// Full resolution pipeline with metadata: DOTNS lookup → IPFS fetch → resolution struct (async).
///
/// Owner lookup and IPFS fetch run concurrently via `futures::join!`.
pub async fn resolve_and_fetch_full(name: &str) -> Result<DotnsResolution, String> {
    let cid = resolve_dotns(name).await?;

    // Run owner lookup and IPFS fetch concurrently.
    let name_for_owner = name.to_string();
    let (owner, assets) = futures::join!(resolve_owner(&name_for_owner), fetch_ipfs(&cid));

    let assets = assets?;
    log::info!("[dotns] owner for {}: {:?}", name, owner);

    Ok(DotnsResolution { cid, owner, assets })
}