//! Reading the Ğ1 indexer (duniter-squid, GraphQL): the comments that carry a
//! given remark, with their author, the author's identity and the transfers of
//! the same transaction.
//!
//! A comment is found by `hash`, the blake2b-256 of the remark's bytes that the
//! chain publishes in its `System.Remarked` event. The indexers of
//! `LD_INDEXERS` are asked in turn: one that does not answer, or answers with
//! errors, is skipped; one that answers « nothing » may be behind, so the next
//! is asked too. Nobody answering is not a « no »: the ballot stays pending.

use crate::AppState;
use ld_engine::address;
use ld_engine::ballot::{ChainIdentity, ChainPosition, Comment, Transfer};
use serde::Deserialize;
use serde_json::json;
use std::time::Duration;

/// Validated on the indexer of the Ğ1 chain (indexer.duniter.org), 2026-10-30.
pub const BALLOT_QUERY: &str = "query Ballot($hash: String!) { txComments(condition: {hash: $hash}, \
    orderBy: BLOCK_NUMBER_ASC, first: 20) { nodes { id blockNumber remark author { id identity { index name \
    isMember } } transfersByCommentId { nodes { fromId toId amount } } } } }";

const TIMEOUT: Duration = Duration::from_secs(6);

#[derive(Deserialize)]
struct Answer {
    data: Option<Data>,
    #[serde(default)]
    errors: Option<serde_json::Value>,
}

#[derive(Deserialize)]
#[serde(rename_all = "camelCase")]
struct Data {
    tx_comments: Nodes<Node>,
}

#[derive(Deserialize)]
struct Nodes<T> {
    nodes: Vec<T>,
}

#[derive(Deserialize)]
#[serde(rename_all = "camelCase")]
struct Node {
    id: String,
    block_number: u32,
    remark: String,
    author: Author,
    transfers_by_comment_id: Nodes<TransferNode>,
}

#[derive(Deserialize)]
struct Author {
    id: String,
    identity: Option<IdentityNode>,
}

#[derive(Deserialize)]
#[serde(rename_all = "camelCase")]
struct IdentityNode {
    index: u32,
    name: String,
    is_member: bool,
}

#[derive(Deserialize)]
#[serde(rename_all = "camelCase")]
struct TransferNode {
    from_id: String,
    to_id: String,
    /// A big integer, served as a string.
    amount: serde_json::Value,
}

/// A comment of the chain, as the engine judges it, with what the server keeps.
#[derive(Clone, Debug)]
pub struct Found {
    pub comment: Comment,
    pub remark: String,
    pub event_id: String,
    /// The account that signed, as a Ğ1 address.
    pub signer: String,
    /// The name of the signer's identity, if any.
    pub name: Option<String>,
}

#[derive(Debug)]
pub enum Reading {
    /// No indexer answered.
    Silent,
    /// The comments found (possibly none).
    Found(Vec<Found>),
}

fn amount(v: &serde_json::Value) -> Option<u64> {
    match v {
        serde_json::Value::String(s) => s.parse().ok(),
        serde_json::Value::Number(n) => n.as_u64(),
        _ => None,
    }
}

fn found(node: Node) -> Option<Found> {
    let position = ChainPosition::from_event_id(&node.id)?;
    if position.block != node.block_number {
        return None;
    }
    let (_, author) = address::decode(&node.author.id)?;
    let transfers = node
        .transfers_by_comment_id
        .nodes
        .iter()
        .map(|t| {
            Some(Transfer {
                from: address::decode(&t.from_id)?.1,
                to: address::decode(&t.to_id)?.1,
                amount: amount(&t.amount)?,
            })
        })
        .collect::<Option<Vec<_>>>()?;
    Some(Found {
        comment: Comment {
            position,
            author,
            identity: node.author.identity.as_ref().map(|i| ChainIdentity { index: i.index, member: i.is_member }),
            transfers,
        },
        remark: node.remark,
        event_id: node.id,
        signer: address::encode(address::G1_PREFIX, &author),
        name: node.author.identity.map(|i| i.name),
    })
}

/// The comments of one answer of the indexer; `None` if it is not one.
pub fn parse(body: &serde_json::Value) -> Option<Vec<Found>> {
    let answer: Answer = serde_json::from_value(body.clone()).ok()?;
    if answer.errors.as_ref().is_some_and(|e| !e.is_null()) {
        return None;
    }
    let nodes = answer.data?.tx_comments.nodes;
    let count = nodes.len();
    let out: Vec<Found> = nodes.into_iter().filter_map(found).collect();
    if out.len() != count {
        tracing::warn!(read = out.len(), served = count, "indexer: comments that do not read were left aside");
    }
    Some(out)
}

/// The comments carrying the remark of hash `remark_hash` (`0x…`).
pub async fn comments(state: &AppState, remark_hash: &str) -> Reading {
    let body = json!({ "query": BALLOT_QUERY, "variables": { "hash": remark_hash } });
    let mut answered = false;
    for url in &state.cfg.indexers {
        let res = state.http.post(url).timeout(TIMEOUT).json(&body).send().await;
        let value: Option<serde_json::Value> = match res {
            Ok(r) if r.status().is_success() => r.json().await.ok(),
            Ok(r) => {
                tracing::debug!(%url, status = %r.status(), "indexer");
                None
            }
            Err(e) => {
                tracing::debug!(%url, error = %e, "indexer");
                None
            }
        };
        match value.as_ref().and_then(parse) {
            Some(list) if !list.is_empty() => return Reading::Found(list),
            Some(_) => answered = true,
            None => {}
        }
    }
    if answered { Reading::Found(Vec::new()) } else { Reading::Silent }
}

#[cfg(test)]
mod tests {
    use super::*;

    /// A real answer of the Ğ1 indexer (2026-10-30), for the remark « Merci ».
    const REAL: &str = include_str!("../tests/fixtures/indexer-merci.json");

    #[test]
    fn a_real_answer_reads() {
        let body: serde_json::Value = serde_json::from_str(REAL).expect("json");
        let list = parse(&body).expect("an answer");
        assert_eq!(list.len(), 4);
        let first = &list[0];
        assert_eq!(first.comment.position, ChainPosition { block: 196_944, event: 3 });
        assert_eq!(first.remark, "Merci ");
        assert_eq!(first.signer, "g1NrqKgJW9FoFabaYW82zhS9tDWdQcL1DGpivaJdj7GW9M6iv");
        assert_eq!(first.name.as_deref(), Some("SIMONEANTONELLI"));
        assert_eq!(first.comment.identity, Some(ChainIdentity { index: 1304, member: true }));
        assert_eq!(first.comment.transfers.len(), 1);
        assert_eq!(first.comment.transfers[0].amount, 30_000);
        assert_eq!(first.comment.transfers[0].from, first.comment.author);
        // An account without identity.
        assert_eq!(list[2].comment.identity, None);
        assert_eq!(list[2].name, None);
    }

    #[test]
    fn errors_or_a_strange_shape_are_no_answer() {
        assert!(parse(&json!({ "errors": [{ "message": "boom" }] })).is_none());
        assert!(parse(&json!({ "data": null })).is_none());
        assert!(parse(&json!({ "nope": 1 })).is_none());
        assert_eq!(parse(&json!({ "data": { "txComments": { "nodes": [] } } })).map(|l| l.len()), Some(0));
    }

    #[test]
    fn a_node_that_does_not_read_is_left_aside() {
        let body = json!({ "data": { "txComments": { "nodes": [
            { "id": "0000000010-abcde-000002", "blockNumber": 11, "remark": "x",
              "author": { "id": "g1NrqKgJW9FoFabaYW82zhS9tDWdQcL1DGpivaJdj7GW9M6iv", "identity": null },
              "transfersByCommentId": { "nodes": [] } },
            { "id": "0000000010-abcde-000002", "blockNumber": 10, "remark": "x",
              "author": { "id": "not an address", "identity": null },
              "transfersByCommentId": { "nodes": [] } },
        ] } } });
        assert_eq!(parse(&body).map(|l| l.len()), Some(0), "block and id disagree; a bad address");
    }
}