use std::sync::mpsc::Sender;

use anyhow::Result;
use serde_json::{json, Value};

use crate::app::AppEvent;
use crate::model::{ExecutionResponse, Plan, PlanStep, SessionSource, TaskConfig};
use crate::process;
use crate::prompt;
use crate::storage::toon;

pub fn implement(
    repo_root: &std::path::Path,
    config: &TaskConfig,
    plan: &Plan,
    step: &PlanStep,
    event_tx: &Sender<AppEvent>,
) -> Result<ExecutionResponse> {
    let goal_md = toon::read_markdown(&config.goal_file)?;
    let standards_md = toon::read_markdown(&config.standards_file)?;
    let context = build_execution_context(plan, step);
    let prompt = format!(
        concat!(
            "You are the autonomous execution worker for a Rust TUI-first controller.\n",
            "Execution mode only. Do not ask the user questions.\n",
            "Complete the active step with the smallest correct change set.\n\n",
            "Efficiency rules:\n",
            "- Inspect only files likely relevant to this step.\n",
            "- Avoid repository-wide searches unless the focused path is exhausted.\n",
            "- Prefer targeted verification and targeted tests over broad full-suite runs.\n",
            "- Keep output terse. Use short summaries and short notes.\n",
            "- If the requested change is already present, return done.\n",
            "- If the goal is genuinely ambiguous, set needs_goal_clarification=true.\n\n",
            "Return empty arrays for verification_commands, test_commands, or notes when not needed.\n\n",
            "Goal summary:\n{goal}\n\n",
            "Standards summary:\n{standards}\n\n",
            "Execution context:\n{context}\n"
        ),
        goal = prompt::compact_markdown(&goal_md, 8, 1200),
        standards = prompt::compact_markdown(&standards_md, 10, 1200),
        context = serde_json::to_string_pretty(&context)?,
    );

    let schema = json!({
      "type": "object",
      "additionalProperties": false,
      "required": ["status", "summary", "verification_commands", "test_commands", "notes", "needs_goal_clarification"],
      "properties": {
        "status": { "type": "string", "enum": ["done", "blocked", "needs-replan"] },
        "summary": { "type": "string" },
        "verification_commands": { "type": "array", "items": { "type": "string" } },
        "test_commands": { "type": "array", "items": { "type": "string" } },
        "notes": { "type": "array", "items": { "type": "string" } },
        "needs_goal_clarification": { "type": "boolean" }
      }
    });
    let raw = process::run_codex_with_schema(
        repo_root,
        &prompt,
        &schema,
        event_tx,
        SessionSource::Executor,
        Some(step.id.clone()),
    )?;
    Ok(serde_json::from_str(&raw)?)
}

fn build_execution_context(plan: &Plan, step: &PlanStep) -> Value {
    let dependency_steps = step
        .dependencies
        .iter()
        .filter_map(|dependency| {
            plan.steps
                .iter()
                .find(|candidate| &candidate.id == dependency)
                .map(|candidate| {
                    json!({
                        "id": candidate.id,
                        "title": prompt::truncate_text(&candidate.title, 100),
                        "status": candidate.status,
                    })
                })
        })
        .collect::<Vec<_>>();

    let next_steps = plan
        .steps
        .iter()
        .filter(|candidate| candidate.id != step.id)
        .filter(|candidate| !candidate.status.is_done())
        .take(3)
        .map(|candidate| {
            json!({
                "id": candidate.id,
                "title": prompt::truncate_text(&candidate.title, 100),
                "dependencies": prompt::compact_string_vec(&candidate.dependencies, 4, 60),
                "status": candidate.status,
            })
        })
        .collect::<Vec<_>>();

    json!({
        "goal_summary": prompt::truncate_text(&plan.goal_summary, 200),
        "active_step": prompt::compact_step(step),
        "dependency_steps": dependency_steps,
        "next_pending_steps": next_steps,
    })
}