use super::agent::AgentNodeExecutor;
use super::executor::StepContext;
use super::llm::LlmNodeExecutor;
use super::progress::{BranchProgressHandle, BranchProgressTracker};
use super::rag::RagNodeExecutor;
use super::state::StateManager;
use super::types::{MapNode, NodeType};
use crate::config::{RenderMode, RequestContext};
use crate::graph::type_name;
use anyhow::{Context, Result, anyhow};
use futures_util::future::join_all;
use serde_json::Value;
use std::collections::HashMap;
use std::sync::Arc;
use tokio::sync::Semaphore;

pub(super) struct MapNodeExecutor;

impl MapNodeExecutor {
    pub(super) async fn execute(
        node: &MapNode,
        state: &mut StateManager,
        ctx: &mut RequestContext,
        step_ctx: &StepContext<'_>,
        node_id: &str,
    ) -> Result<()> {
        let over_value = state
            .interpolate_raw(&node.over)
            .with_context(|| format!("map node '{node_id}': evaluating `over` template"))?;

        let items = over_value.as_array().ok_or_else(|| {
            anyhow!(
                "map node '{}': `over` template '{}' must resolve to an array, got {}",
                node_id,
                node.over,
                type_name(&over_value)
            )
        })?;
        let items = items.clone();

        let branch_node = step_ctx
            .graph
            .get_node(&node.branch)
            .ok_or_else(|| {
                anyhow!(
                    "map node '{node_id}': branch '{}' not found in graph",
                    node.branch
                )
            })?
            .clone();

        let max_conc = node
            .max_concurrency
            .unwrap_or(step_ctx.max_concurrency)
            .max(1);
        let semaphore = Arc::new(Semaphore::new(max_conc));
        let progress_tracker = BranchProgressTracker::new();
        let mut sub_tasks = Vec::with_capacity(items.len());

        for (idx, item) in items.iter().enumerate() {
            let item = item.clone();
            let as_name = node.as_name.clone();
            let branch_clone = branch_node.clone();
            let mut sub_state = state.fork_for_branch_state();
            let mut sub_ctx = ctx.fork_for_branch();
            sub_ctx.render_mode = RenderMode::Silent;
            let script_clone = step_ctx.script_executor.clone();
            let sub_branch_id = node.branch.clone();
            let sem = semaphore.clone();
            let abort = step_ctx.abort_signal.clone();
            let progress_handle: BranchProgressHandle =
                progress_tracker.add_branch(&format!("{}[{idx}]", node.branch));

            sub_state.state_mut().set(as_name, item);

            let task = tokio::spawn(async move {
                let mut progress_handle = Some(progress_handle);
                let _permit = sem
                    .acquire()
                    .await
                    .expect("map semaphore should not be closed");
                if abort.aborted() {
                    if let Some(h) = progress_handle.take() {
                        h.fail("aborted");
                    }
                    return (
                        idx,
                        sub_state,
                        Err(anyhow!("map sub-branch [{idx}] aborted")),
                    );
                }
                let mut state = sub_state;
                let mut ctx = sub_ctx;

                let exec_result: Result<()> = match &branch_clone.node_type {
                    NodeType::Llm(n) => LlmNodeExecutor::execute(n, &mut state, &mut ctx)
                        .await
                        .map(|_| ()),
                    NodeType::Agent(n) => AgentNodeExecutor::execute(n, &mut state, &mut ctx)
                        .await
                        .map(|_| ()),
                    NodeType::Rag(n) => {
                        RagNodeExecutor::execute(n, &sub_branch_id, &mut state, &mut ctx).await
                    }
                    NodeType::Script(n) => script_clone.execute(n, &mut state).await.map(|_| ()),
                    _ => Err(anyhow!(
                        "map branch '{}' has type that cannot run inside a map \
                         (validator should have caught this; internal error)",
                        branch_clone.id
                    )),
                };

                if let Some(h) = progress_handle.take() {
                    match &exec_result {
                        Ok(_) => h.complete(),
                        Err(e) => h.fail(&e.to_string()),
                    }
                }

                (idx, state, exec_result)
            });
            sub_tasks.push(task);
        }

        let joined = join_all(sub_tasks).await;
        drop(progress_tracker);

        // Collect outputs keyed by input index so order is preserved regardless
        // of finish order. This is the user-facing contract from plan E.2.
        let mut outputs: HashMap<usize, Value> = HashMap::new();
        for join_result in joined {
            let (idx, sub_state, exec_result) =
                join_result.map_err(|e| anyhow!("map sub-branch panicked: {e}"))?;

            exec_result
                .with_context(|| format!("map node '{node_id}': sub-branch [{idx}] failed"))?;

            let output_value = sub_state
                .state()
                .get(&node.output_key)
                .cloned()
                .ok_or_else(|| {
                    anyhow!(
                        "map node '{node_id}': sub-branch [{idx}] did not write \
                         `output_key` '{}'",
                        node.output_key
                    )
                })?;

            outputs.insert(idx, output_value);
        }

        let mut collected = Vec::with_capacity(items.len());
        for idx in 0..items.len() {
            let value = outputs.remove(&idx).ok_or_else(|| {
                anyhow!(
                    "map node '{node_id}': internal error: missing result for sub-branch [{idx}]"
                )
            })?;
            collected.push(value);
        }

        state
            .state_mut()
            .set(node.collect_into.clone(), Value::Array(collected));

        Ok(())
    }
}