//! ElectrumX sync status: fetches indexed height from Electrum RPC and network height from Bitcoin Core.

use anyhow::{Context, Result};
use serde::Serialize;
use std::time::Duration;
use tokio::io::{AsyncBufReadExt, AsyncWriteExt, BufReader};
use tokio::net::TcpStream;

const ELECTRUMX_HOST: &str = "127.0.0.1";
const ELECTRUMX_PORT: u16 = 50001;
const ELECTRUMX_DATA_DIR: &str = "/var/lib/archipelago/electrumx";
// Approximate final index size in bytes for mainnet (~130GB for ElectrumX full index as of 2026)
const ESTIMATED_FULL_INDEX_BYTES: f64 = 130_000_000_000.0;

/// Build Bitcoin RPC Basic auth header using shared credentials.
async fn bitcoin_rpc_auth() -> String {
    let (user, pass) = crate::bitcoin_rpc::bitcoin_rpc_credentials().await;
    use base64::Engine;
    let encoded = base64::engine::general_purpose::STANDARD.encode(format!("{}:{}", user, pass));
    format!("Basic {}", encoded)
}

#[derive(Debug, Serialize)]
pub struct ElectrsSyncStatus {
    pub indexed_height: u64,
    pub network_height: u64,
    pub progress_pct: f64,
    pub status: String,
    pub error: Option<String>,
    /// Index data size in human-readable format (e.g. "11.2 GB")
    pub index_size: Option<String>,
    /// Tor onion address for ElectrumX (if available)
    pub tor_onion: Option<String>,
}

/// Get the total size of a directory in bytes.
async fn dir_size_bytes(path: &str) -> u64 {
    let mut total: u64 = 0;
    let mut entries = match tokio::fs::read_dir(path).await {
        Ok(entries) => entries,
        Err(_) => return 0,
    };
    while let Ok(Some(entry)) = entries.next_entry().await {
        let entry_path = entry.path();
        if entry_path.is_dir() {
            total += Box::pin(dir_size_bytes(&entry_path.to_string_lossy())).await;
        } else if let Ok(meta) = entry.metadata().await {
            total += meta.len();
        }
    }
    total
}

/// Format bytes as human-readable string.
fn format_bytes(bytes: u64) -> String {
    if bytes >= 1_000_000_000 {
        format!("{:.1} GB", bytes as f64 / 1_000_000_000.0)
    } else if bytes >= 1_000_000 {
        format!("{:.1} MB", bytes as f64 / 1_000_000.0)
    } else {
        format!("{} KB", bytes / 1_000)
    }
}

/// Fetch ElectrumX indexed height via Electrum protocol (TCP JSON-RPC).
async fn electrumx_indexed_height() -> Result<u64> {
    let timeout_duration = Duration::from_secs(5);

    let stream = tokio::time::timeout(
        timeout_duration,
        TcpStream::connect((ELECTRUMX_HOST, ELECTRUMX_PORT)),
    )
    .await
    .context("ElectrumX connection timed out")?
    .context("Failed to connect to ElectrumX")?;

    let (reader_half, mut writer_half) = tokio::io::split(stream);

    // blockchain.headers.subscribe returns {"height": N, "hex": "..."}
    let req = r#"{"id":1,"method":"blockchain.headers.subscribe","params":[]}
"#;
    tokio::time::timeout(timeout_duration, writer_half.write_all(req.as_bytes()))
        .await
        .context("ElectrumX write timed out")?
        .context("Failed to write to ElectrumX")?;

    tokio::time::timeout(timeout_duration, writer_half.flush())
        .await
        .context("ElectrumX flush timed out")?
        .context("Failed to flush ElectrumX stream")?;

    let mut reader = BufReader::new(reader_half);
    let mut line = String::new();
    tokio::time::timeout(timeout_duration, reader.read_line(&mut line))
        .await
        .context("ElectrumX read timed out")?
        .context("Failed to read from ElectrumX")?;

    let line = line.trim();
    if line.is_empty() {
        anyhow::bail!("Empty response from ElectrumX");
    }

    let json: serde_json::Value = serde_json::from_str(line)?;
    // blockchain.numblocks.subscribe returns result as number; headers.subscribe returns {block_height: N, hex: ...}
    let height = json
        .get("result")
        .and_then(|r| r.as_u64())
        .or_else(|| {
            json.get("result")
                .and_then(|r| r.get("block_height"))
                .and_then(|h| h.as_u64())
        })
        .or_else(|| {
            // ElectrumX returns {"result": {"height": N, "hex": "..."}}
            json.get("result")
                .and_then(|r| r.get("height"))
                .and_then(|h| h.as_u64())
        })
        .context("Missing height in ElectrumX response")?;
    Ok(height)
}

/// Fetch Bitcoin network height via JSON-RPC.
async fn bitcoin_network_height() -> Result<u64> {
    let client = reqwest::Client::new();
    let body = serde_json::json!({
        "jsonrpc": "1.0",
        "id": "electrs-status",
        "method": "getblockcount",
        "params": []
    });
    let resp = client
        .post(crate::constants::BITCOIN_RPC_URL)
        .header("Content-Type", "application/json")
        .header("Authorization", bitcoin_rpc_auth().await)
        .body(body.to_string())
        .send()
        .await
        .context("Bitcoin RPC request failed")?;

    if !resp.status().is_success() {
        anyhow::bail!("Bitcoin RPC returned {}", resp.status());
    }

    let json: serde_json::Value = resp.json().await?;
    let height = json
        .get("result")
        .and_then(|r| r.as_u64())
        .context("Missing result in Bitcoin RPC")?;
    Ok(height)
}

/// Get ElectrumX sync status.
pub async fn get_electrs_sync_status() -> ElectrsSyncStatus {
    // Get index data size
    let data_bytes = dir_size_bytes(ELECTRUMX_DATA_DIR).await;
    let index_size = if data_bytes > 0 {
        Some(format_bytes(data_bytes))
    } else {
        None
    };

    // Read Tor onion address — check system Tor path first, then legacy
    let tor_onion = {
        let mut onion = None;
        for path in &[
            "/var/lib/archipelago/tor-hostnames/electrs",
            "/var/lib/tor/hidden_service_electrs/hostname",
            "/var/lib/archipelago/tor/hidden_service_electrs/hostname",
        ] {
            if let Ok(addr) = tokio::fs::read_to_string(path).await {
                let addr = addr.trim().to_string();
                if addr.ends_with(".onion") {
                    onion = Some(addr);
                    break;
                }
            }
            if let Ok(output) = tokio::process::Command::new("sudo")
                .args(["cat", path])
                .output()
                .await
            {
                if output.status.success() {
                    let addr = String::from_utf8_lossy(&output.stdout).trim().to_string();
                    if addr.ends_with(".onion") {
                        onion = Some(addr);
                        break;
                    }
                }
            }
        }
        onion
    };

    let network_height = match bitcoin_network_height().await {
        Ok(h) => h,
        Err(e) => {
            return ElectrsSyncStatus {
                indexed_height: 0,
                network_height: 0,
                progress_pct: 0.0,
                status: "error".to_string(),
                error: Some(format!("Bitcoin RPC: {}", e)),
                index_size,
                tor_onion,
            };
        }
    };

    let indexed_height = match electrumx_indexed_height().await {
        Ok(h) => h,
        Err(e) => {
            // ElectrumX may not be ready on 50001 during initial sync
            let err_msg = e.to_string();
            let err_lower = err_msg.to_lowercase();
            let (status, error) = if err_lower.contains("connect") || err_lower.contains("reset") || err_lower.contains("refused") || err_lower.contains("timed out") {
                // Estimate progress from data directory size
                let _est_pct = if data_bytes > 0 {
                    ((data_bytes as f64 / ESTIMATED_FULL_INDEX_BYTES) * 100.0).min(99.0)
                } else {
                    0.0
                };
                let size_str = index_size.clone().unwrap_or_else(|| "0 MB".to_string());
                (
                    "indexing".to_string(),
                    Some(format!(
                        "Building index ({} / ~130 GB estimated). Electrum RPC will be available when complete.",
                        size_str
                    )),
                )
            } else {
                ("error".to_string(), Some(format!("ElectrumX: {}", e)))
            };
            // Use estimated progress when indexing
            let progress_pct = if status == "indexing" && data_bytes > 0 {
                ((data_bytes as f64 / ESTIMATED_FULL_INDEX_BYTES) * 100.0).min(99.0)
            } else {
                0.0
            };
            return ElectrsSyncStatus {
                indexed_height: 0,
                network_height,
                progress_pct,
                status,
                error,
                index_size,
                tor_onion: tor_onion.clone(),
            };
        }
    };

    let progress_pct = if network_height > 0 {
        (indexed_height as f64 / network_height as f64) * 100.0
    } else {
        0.0
    };

    let status = if indexed_height >= network_height.saturating_sub(1) {
        "synced"
    } else {
        "syncing"
    };

    ElectrsSyncStatus {
        indexed_height,
        network_height,
        progress_pct,
        status: status.to_string(),
        error: None,
        index_size,
        tor_onion,
    }
}