//! Prints Zebra checkpoints as "height hash" output lines.
//!
//! Get all the blocks up to network current tip and print the ones that are
//! checkpoints according to rules.
//!
//! For usage please refer to the program help: `zebra-checkpoints --help`
//!
//! zebra-consensus accepts an ordered list of checkpoints, starting with the
//! genesis block. Checkpoint heights can be chosen arbitrarily.

use std::{ffi::OsString, process::Stdio};

#[cfg(unix)]
use std::os::unix::process::ExitStatusExt;

use color_eyre::{
    eyre::{ensure, eyre, Result},
    Help,
};
use itertools::Itertools;
use serde_json::Value;
use structopt::StructOpt;

use zebra_chain::{
    block::{self, Block, Height, HeightDiff, TryIntoHeight},
    serialization::ZcashDeserializeInto,
    transparent::MIN_TRANSPARENT_COINBASE_MATURITY,
};
use zebra_node_services::{
    constants::{MAX_CHECKPOINT_BYTE_COUNT, MAX_CHECKPOINT_HEIGHT_GAP},
    rpc_client::RpcRequestClient,
};
use zebra_utils::init_tracing;

pub mod args;

use args::{Args, Backend, Transport};

/// Make an RPC call based on `our_args` and `rpc_command`, and return the response as a [`Value`].
async fn rpc_output<M, I>(our_args: &Args, method: M, params: I) -> Result<Value>
where
    M: AsRef<str>,
    I: IntoIterator<Item = String>,
{
    match our_args.transport {
        Transport::Cli => cli_output(our_args, method, params),
        Transport::Direct => direct_output(our_args, method, params).await,
    }
}

/// Connect to the node with `our_args` and `rpc_command`, and return the response as a [`Value`].
///
/// Only used if the transport is [`Direct`](Transport::Direct).
async fn direct_output<M, I>(our_args: &Args, method: M, params: I) -> Result<Value>
where
    M: AsRef<str>,
    I: IntoIterator<Item = String>,
{
    // Get a new RPC client that will connect to our node
    let addr = our_args
        .addr
        .unwrap_or_else(|| "127.0.0.1:8232".parse().expect("valid address"));
    let client = RpcRequestClient::new(addr);

    // Launch a request with the RPC method and arguments
    //
    // The params are a JSON array with typed arguments.
    // TODO: accept JSON value arguments, and do this formatting using serde_json
    let params = format!("[{}]", params.into_iter().join(", "));
    let response = client.text_from_call(method, params).await?;

    // Extract the "result" field from the RPC response
    let mut response: Value = serde_json::from_str(&response)?;
    let response = response["result"].take();

    Ok(response)
}

/// Run `cmd` with `our_args` and `rpc_command`, and return its output as a [`Value`].
///
/// Only used if the transport is [`Cli`](Transport::Cli).
fn cli_output<M, I>(our_args: &Args, method: M, params: I) -> Result<Value>
where
    M: AsRef<str>,
    I: IntoIterator<Item = String>,
{
    // Get a new `zcash-cli` command configured for our node,
    // including the `zebra-checkpoints` passthrough arguments.
    let mut cmd = std::process::Command::new(&our_args.cli);
    cmd.args(&our_args.zcli_args);

    // Turn the address into command-line arguments
    if let Some(addr) = our_args.addr {
        cmd.arg(format!("-rpcconnect={}", addr.ip()));
        cmd.arg(format!("-rpcport={}", addr.port()));
    }

    // Add the RPC method and arguments
    let method: OsString = method.as_ref().into();
    cmd.arg(method);

    for param in params {
        // Remove JSON string/int type formatting, because zcash-cli will add it anyway
        // TODO: accept JSON value arguments, and do this formatting using serde_json?
        let param = param.trim_matches('"');
        let param: OsString = param.into();
        cmd.arg(param);
    }

    // Launch a CLI request, capturing stdout, but sending stderr to the user
    let output = cmd.stderr(Stdio::inherit()).output()?;

    // Make sure the command was successful
    #[cfg(unix)]
    ensure!(
        output.status.success(),
        "Process failed: exit status {:?}, signal: {:?}",
        output.status.code(),
        output.status.signal()
    );
    #[cfg(not(unix))]
    ensure!(
        output.status.success(),
        "Process failed: exit status {:?}",
        output.status.code()
    );

    // Make sure the output is valid UTF-8 JSON
    let response = String::from_utf8(output.stdout)?;
    // zcash-cli returns raw strings without JSON type info.
    // As a workaround, assume that invalid responses are strings.
    let response: Value = serde_json::from_str(&response)
        .unwrap_or_else(|_error| Value::String(response.trim().to_string()));

    Ok(response)
}

/// Process entry point for `zebra-checkpoints`
#[tokio::main]
#[allow(clippy::print_stdout, clippy::print_stderr)]
async fn main() -> Result<()> {
    eprintln!("zebra-checkpoints launched");

    // initialise
    init_tracing();
    color_eyre::install()?;

    let args = args::Args::from_args();

    eprintln!("Command-line arguments: {args:?}");
    eprintln!("Fetching block info and calculating checkpoints...\n\n");

    // get the current block count
    let get_block_chain_info = rpc_output(&args, "getblockchaininfo", None)
        .await
        .with_suggestion(|| {
            "Is the RPC server address and port correct? Is authentication configured correctly?"
        })?;

    // calculate the maximum height
    let height_limit = get_block_chain_info["blocks"]
        .try_into_height()
        .expect("height: unexpected invalid value, missing field, or field type");

    // Checkpoints must be on the main chain, so we skip blocks that are within the
    // Zcash reorg limit.
    let height_limit = height_limit - HeightDiff::from(MIN_TRANSPARENT_COINBASE_MATURITY);
    let height_limit = height_limit
        .ok_or_else(|| {
            eyre!(
                "checkpoint generation needs at least {:?} blocks",
                MIN_TRANSPARENT_COINBASE_MATURITY
            )
        })
        .with_suggestion(|| "Hint: wait for the node to sync more blocks")?;

    // Start at the next block after the last checkpoint.
    // If there is no last checkpoint, start at genesis (height 0).
    let starting_height = if let Some(last_checkpoint) = args.last_checkpoint {
        (last_checkpoint + 1)
            .expect("invalid last checkpoint height, must be less than the max height")
    } else {
        Height::MIN
    };

    assert!(
        starting_height < height_limit,
        "checkpoint generation needs more blocks than the starting height {starting_height:?}. \
         Hint: wait for the node to sync more blocks"
    );

    // set up counters
    let mut cumulative_bytes: u64 = 0;
    let mut last_checkpoint_height = args.last_checkpoint.unwrap_or(Height::MIN);
    let max_checkpoint_height_gap =
        HeightDiff::try_from(MAX_CHECKPOINT_HEIGHT_GAP).expect("constant fits in HeightDiff");

    // loop through all blocks
    for request_height in starting_height.0..height_limit.0 {
        // In `Cli` transport mode we need to create a process for each block

        let (hash, response_height, size) = match args.backend {
            Backend::Zcashd => {
                // get block data from zcashd using verbose=1
                let get_block = rpc_output(
                    &args,
                    "getblock",
                    [format!(r#""{request_height}""#), 1.to_string()],
                )
                .await?;

                // get the values we are interested in
                let hash: block::Hash = get_block["hash"]
                    .as_str()
                    .expect("hash: unexpected missing field or field type")
                    .parse()?;
                let response_height: Height = get_block["height"]
                    .try_into_height()
                    .expect("height: unexpected invalid value, missing field, or field type");

                let size = get_block["size"]
                    .as_u64()
                    .expect("size: unexpected invalid value, missing field, or field type");

                (hash, response_height, size)
            }
            Backend::Zebrad => {
                // get block data from zebrad (or zcashd) by deserializing the raw block
                let block_bytes = rpc_output(
                    &args,
                    "getblock",
                    [format!(r#""{request_height}""#), 0.to_string()],
                )
                .await?;
                let block_bytes = block_bytes
                    .as_str()
                    .expect("block bytes: unexpected missing field or field type");

                let block_bytes: Vec<u8> = hex::decode(block_bytes)?;

                // TODO: is it faster to call both `getblock height verbosity=0`
                //       and `getblock height verbosity=1`, rather than deserializing the block
                //       and calculating its hash?
                //
                // It seems to be fast enough for checkpoint updates for now,
                // but generating the full list takes more than an hour.
                let block: Block = block_bytes.zcash_deserialize_into()?;

                (
                    block.hash(),
                    block
                        .coinbase_height()
                        .expect("valid blocks always have a coinbase height"),
                    block_bytes.len().try_into()?,
                )
            }
        };

        assert_eq!(
            request_height, response_height.0,
            "node returned a different block than requested"
        );

        // compute cumulative totals
        cumulative_bytes += size;

        let height_gap = response_height - last_checkpoint_height;

        // check if this block should be a checkpoint
        if response_height == Height::MIN
            || cumulative_bytes >= MAX_CHECKPOINT_BYTE_COUNT
            || height_gap >= max_checkpoint_height_gap
        {
            // print to output
            println!("{} {hash}", response_height.0);

            // reset cumulative totals
            cumulative_bytes = 0;
            last_checkpoint_height = response_height;
        }
    }

    Ok(())
}