//! Gemini-native endpoint (/v1/gemini) — zero-translation tool call passthrough.
//!
//! Accepts tools in Gemini `functionDeclarations` format directly,
//! returns `functionCall` in Gemini format directly.
//! No OpenAI ↔ Gemini format conversion.

use axum::{
    extract::State,
    http::StatusCode,
    response::{IntoResponse, Json},
};
use std::sync::Arc;
use tracing::info;

use super::models::{lookup_model, DEFAULT_MODEL, MODELS};
use super::polling::poll_for_response;
use super::util::{err_response, now_unix};
use super::AppState;
use crate::mitm::store::PendingToolResult;

/// Gemini-native request format.
#[derive(serde::Deserialize)]
pub(crate) struct GeminiRequest {
    pub model: Option<String>,
    /// User input text.
    pub input: serde_json::Value,
    /// Gemini-native tools: [{"functionDeclarations": [...]}]
    #[serde(default)]
    pub tools: Option<Vec<serde_json::Value>>,
    /// Gemini-native toolConfig: {"functionCallingConfig": {"mode": "AUTO"}}
    #[serde(default)]
    pub tool_config: Option<serde_json::Value>,
    /// Session/conversation ID.
    #[serde(default)]
    pub conversation: Option<serde_json::Value>,
    #[serde(default = "default_timeout")]
    pub timeout: u64,
    #[serde(default)]
    pub stream: bool,
    /// Tool results in Gemini format: [{"functionResponse": {"name": "...", "response": {...}}}]
    #[serde(default)]
    pub tool_results: Option<Vec<serde_json::Value>>,
}

fn default_timeout() -> u64 {
    120
}

fn extract_conversation_id(conv: &Option<serde_json::Value>) -> Option<String> {
    match conv {
        Some(serde_json::Value::String(s)) => Some(s.clone()),
        Some(obj) => obj["id"].as_str().map(|s| s.to_string()),
        None => None,
    }
}

pub(crate) async fn handle_gemini(
    State(state): State<Arc<AppState>>,
    Json(body): Json<GeminiRequest>,
) -> axum::response::Response {
    info!(
        "POST /v1/gemini model={} stream={}",
        body.model.as_deref().unwrap_or(DEFAULT_MODEL),
        body.stream
    );

    let model_name = body.model.as_deref().unwrap_or(DEFAULT_MODEL);
    let model = match lookup_model(model_name) {
        Some(m) => m,
        None => {
            let names: Vec<&str> = MODELS.iter().map(|m| m.name).collect();
            return err_response(
                StatusCode::BAD_REQUEST,
                format!("Unknown model: {model_name}. Available: {names:?}"),
                "invalid_request_error",
            );
        }
    };

    let token = state.backend.oauth_token().await;
    if token.is_empty() {
        return err_response(
            StatusCode::UNAUTHORIZED,
            "No OAuth token. POST to /v1/token or set ANTIGRAVITY_OAUTH_TOKEN env var.".into(),
            "authentication_error",
        );
    }

    // Extract user text
    let user_text = match &body.input {
        serde_json::Value::String(s) => s.clone(),
        _ => {
            return err_response(
                StatusCode::BAD_REQUEST,
                "Gemini endpoint requires input as a string".to_string(),
                "invalid_request_error",
            );
        }
    };

    // Store tools directly in Gemini format (no conversion needed!)
    if let Some(ref tools) = body.tools {
        if !tools.is_empty() {
            state.mitm_store.set_tools(tools.clone()).await;
            info!(count = tools.len(), "Stored Gemini-native tools for MITM injection");
        }
    }
    if let Some(ref config) = body.tool_config {
        state.mitm_store.set_tool_config(config.clone()).await;
    }

    // Handle tool results (Gemini format: functionResponse)
    if let Some(ref results) = body.tool_results {
        for r in results {
            if let Some(fr) = r.get("functionResponse") {
                let name = fr["name"].as_str().unwrap_or("unknown").to_string();
                let response = fr.get("response").cloned().unwrap_or(serde_json::json!({}));
                state.mitm_store.add_tool_result(PendingToolResult {
                    name,
                    result: response,
                }).await;
            }
        }
        info!(count = results.len(), "Stored Gemini-native tool results for MITM injection");
    }

    // Session/conversation management
    let session_id_str = extract_conversation_id(&body.conversation);
    let cascade_id = if let Some(ref sid) = session_id_str {
        match state
            .sessions
            .get_or_create(Some(sid), || state.backend.create_cascade())
            .await
        {
            Ok(sr) => sr.cascade_id,
            Err(e) => {
                return err_response(
                    StatusCode::BAD_GATEWAY,
                    format!("StartCascade failed: {e}"),
                    "server_error",
                );
            }
        }
    } else {
        match state.backend.create_cascade().await {
            Ok(cid) => cid,
            Err(e) => {
                return err_response(
                    StatusCode::BAD_GATEWAY,
                    format!("StartCascade failed: {e}"),
                    "server_error",
                );
            }
        }
    };

    // Send message
    match state
        .backend
        .send_message(&cascade_id, &user_text, model.model_enum)
        .await
    {
        Ok((200, _)) => {
            let bg = Arc::clone(&state.backend);
            let cid = cascade_id.clone();
            tokio::spawn(async move {
                let _ = bg.update_annotations(&cid).await;
            });
        }
        Ok((status, _)) => {
            return err_response(
                StatusCode::BAD_GATEWAY,
                format!("Antigravity returned {status}"),
                "server_error",
            );
        }
        Err(e) => {
            return err_response(
                StatusCode::BAD_GATEWAY,
                format!("Send message failed: {e}"),
                "server_error",
            );
        }
    }

    let has_custom_tools = state.mitm_store.get_tools().await.is_some();

    // Clear stale response
    state.mitm_store.clear_response_async().await;

    // ── MITM bypass: when tools active, poll MitmStore directly ──
    if has_custom_tools {
        let start = std::time::Instant::now();
        while start.elapsed().as_secs() < body.timeout {
            // Check for function calls
            let captured = state.mitm_store.take_any_function_calls().await;
            if let Some(ref calls) = captured {
                if !calls.is_empty() {
                    let parts: Vec<serde_json::Value> = calls
                        .iter()
                        .map(|fc| {
                            serde_json::json!({
                                "functionCall": {
                                    "name": fc.name,
                                    "args": fc.args,
                                }
                            })
                        })
                        .collect();

                    return Json(serde_json::json!({
                        "candidates": [{
                            "content": {
                                "parts": parts,
                                "role": "model",
                            },
                            "finishReason": "STOP",
                        }],
                        "modelVersion": model_name,
                    }))
                    .into_response();
                }
            }

            // Check for completed text response
            if state.mitm_store.is_response_complete() {
                let text = state.mitm_store.take_response_text().await.unwrap_or_default();
                return Json(serde_json::json!({
                    "candidates": [{
                        "content": {
                            "parts": [{"text": text}],
                            "role": "model",
                        },
                        "finishReason": "STOP",
                    }],
                    "modelVersion": model_name,
                }))
                .into_response();
            }

            tokio::time::sleep(tokio::time::Duration::from_millis(200)).await;
        }

        // Timeout
        return Json(serde_json::json!({
            "error": {
                "message": "Request timed out",
                "type": "timeout_error",
            }
        }))
        .into_response();
    }

    // ── Normal LS path (no custom tools) ──
    // Poll for response
    let poll_result = poll_for_response(&state, &cascade_id, body.timeout).await;

    // Check for captured function calls — return in Gemini format
    let captured_tool_calls = state.mitm_store.take_any_function_calls().await;

    if let Some(ref calls) = captured_tool_calls {
        info!(
            count = calls.len(),
            tools = ?calls.iter().map(|c| &c.name).collect::<Vec<_>>(),
            "Returning captured function calls (Gemini format)"
        );

        let parts: Vec<serde_json::Value> = calls
            .iter()
            .map(|fc| {
                serde_json::json!({
                    "functionCall": {
                        "name": fc.name,
                        "args": fc.args,
                    }
                })
            })
            .collect();

        return Json(serde_json::json!({
            "candidates": [{
                "content": {
                    "parts": parts,
                    "role": "model",
                },
                "finishReason": "STOP",
            }],
            "modelVersion": model_name,
        }))
        .into_response();
    }

    // Normal text response
    Json(serde_json::json!({
        "candidates": [{
            "content": {
                "parts": [{"text": poll_result.text}],
                "role": "model",
            },
            "finishReason": "STOP",
        }],
        "modelVersion": model_name,
    }))
    .into_response()
}