// First consumer lands in a later PR (hybrid backend routing). Tests exercise
// the translation helpers directly.
#![allow(dead_code)]

use anyhow::Context as _;
use anyhow::{Result, anyhow, bail};
use async_trait::async_trait;
use opentelemetry::trace::Status;
use reqwest::Client;
use serde::Deserialize;
use serde_json::{Value, json};
use std::collections::HashMap;
use std::sync::{Arc, Mutex};
use std::time::{Duration, Instant};
use tracing_opentelemetry::OpenTelemetrySpanExt as _;

use crate::ai::llm_client::{
    ChatMessage, LlmClient, LlmStreamEvent, ModelCapabilities, Tool, ToolCall, ToolCallFunction,
};

use futures::stream::{BoxStream, StreamExt};

const DEFAULT_BASE_URL: &str = "https://openrouter.ai/api/v1";
const DEFAULT_EMBEDDING_MODEL: &str = "openai/text-embedding-3-small";
const CACHE_DURATION_SECS: u64 = 15 * 60;
/// Default completion cap sent as `max_tokens`. OpenRouter pre-authorizes
/// credit against the requested max (defaulting to the model's full output
/// window when omitted), so expensive models fail with credit-limit errors
/// even when the actual reply is short. Override via `openrouter.max_tokens`.
pub const DEFAULT_MAX_TOKENS: u32 = 16384;

#[derive(Clone)]
struct CachedEntry<T> {
    data: T,
    cached_at: Instant,
}

impl<T> CachedEntry<T> {
    fn new(data: T) -> Self {
        Self {
            data,
            cached_at: Instant::now(),
        }
    }

    fn is_expired(&self) -> bool {
        self.cached_at.elapsed().as_secs() > CACHE_DURATION_SECS
    }
}

/// The error every image-carrying OpenRouter request fails with.
pub const IMAGES_STAY_LOCAL: &str = "refusing to send image data to OpenRouter: photos stay on \
     the local network (describe them with the local vision model and send the text)";

lazy_static::lazy_static! {
    static ref MODEL_CAPABILITIES_CACHE: Arc<Mutex<HashMap<String, CachedEntry<Vec<ModelCapabilities>>>>> =
        Arc::new(Mutex::new(HashMap::new()));
}

/// OpenAI-compatible client for OpenRouter (https://openrouter.ai).
///
/// Translates canonical `ChatMessage` / `Tool` shapes to OpenAI wire format:
/// - Tool-call `arguments` serialized as JSON-encoded strings (vs Ollama's
///   native JSON).
/// - **Never sends images.** Photos stay on the local network: hybrid mode
///   describes them with the local vision model and sends only the text.
///   A message that still carries image data is refused (see
///   [`IMAGES_STAY_LOCAL`]) rather than uploaded, so a caller bug fails a
///   turn instead of leaking a photo.
/// - `role=tool` messages attach a `tool_call_id` inferred from the preceding
///   assistant turn's tool call.
#[derive(Clone)]
pub struct OpenRouterClient {
    client: Client,
    pub api_key: String,
    pub base_url: String,
    pub primary_model: String,
    pub embedding_model: String,
    num_ctx: Option<i32>,
    temperature: Option<f32>,
    top_p: Option<f32>,
    top_k: Option<i32>,
    min_p: Option<f32>,
    /// Upper bound on generated tokens per call, sent as `max_tokens`.
    /// `None` omits the field (provider default).
    max_tokens: Option<u32>,
    /// Optional `HTTP-Referer` header OpenRouter uses for attribution.
    pub referer: Option<String>,
    /// Optional `X-Title` header OpenRouter uses for attribution.
    pub app_title: Option<String>,
}

impl OpenRouterClient {
    pub fn new(api_key: String, base_url: Option<String>, primary_model: String) -> Self {
        Self {
            client: Client::builder()
                .connect_timeout(Duration::from_secs(10))
                .timeout(Duration::from_secs(180))
                .build()
                .unwrap_or_else(|_| Client::new()),
            api_key,
            base_url: base_url.unwrap_or_else(|| DEFAULT_BASE_URL.to_string()),
            primary_model,
            embedding_model: DEFAULT_EMBEDDING_MODEL.to_string(),
            num_ctx: None,
            temperature: None,
            top_p: None,
            top_k: None,
            min_p: None,
            max_tokens: Some(DEFAULT_MAX_TOKENS),
            referer: None,
            app_title: None,
        }
    }

    pub fn set_embedding_model(&mut self, model: String) {
        self.embedding_model = model;
    }

    #[allow(dead_code)]
    pub fn set_num_ctx(&mut self, num_ctx: Option<i32>) {
        self.num_ctx = num_ctx;
    }

    #[allow(dead_code)]
    pub fn set_sampling_params(
        &mut self,
        temperature: Option<f32>,
        top_p: Option<f32>,
        top_k: Option<i32>,
        min_p: Option<f32>,
    ) {
        self.temperature = temperature;
        self.top_p = top_p;
        self.top_k = top_k;
        self.min_p = min_p;
    }

    pub fn set_max_tokens(&mut self, max_tokens: Option<u32>) {
        self.max_tokens = max_tokens;
    }

    pub fn set_attribution(&mut self, referer: Option<String>, app_title: Option<String>) {
        self.referer = referer;
        self.app_title = app_title;
    }

    fn authed(&self, builder: reqwest::RequestBuilder) -> reqwest::RequestBuilder {
        let mut b = builder.bearer_auth(&self.api_key);
        if let Some(r) = &self.referer {
            b = b.header("HTTP-Referer", r);
        }
        if let Some(t) = &self.app_title {
            b = b.header("X-Title", t);
        }
        b
    }

    /// Start the `llm.request` span for an outgoing call. `operation` is
    /// `chat`, `embeddings`, or `describe` — the call shape, not the entry
    /// point (a `describe_image` funneled through `chat_with_tools` is
    /// still a `describe`).
    fn start_request_span(&self, operation: &str, model: &str) -> tracing::Span {
        crate::otel::start_llm_request_span("openrouter", operation, model)
    }

    /// Translate canonical messages to the OpenAI-compatible wire shape.
    ///
    /// Walks in order so it can attach `tool_call_id` to `role=tool` messages
    /// based on the most recent assistant turn's tool call.
    ///
    /// Errors if any message carries image data: this is the one choke point
    /// every OpenRouter request passes through, so the "photos never leave
    /// the network" rule is enforced here rather than trusted to callers.
    fn messages_to_openai(messages: &[ChatMessage]) -> Result<Vec<Value>> {
        if messages
            .iter()
            .any(|m| m.images.as_ref().is_some_and(|imgs| !imgs.is_empty()))
        {
            log::error!("{IMAGES_STAY_LOCAL}");
            bail!(IMAGES_STAY_LOCAL);
        }
        let mut out = Vec::with_capacity(messages.len());
        let mut last_tool_call_ids: Vec<String> = Vec::new();
        let mut next_tool_result_idx: usize = 0;

        for msg in messages {
            let mut obj = serde_json::Map::new();
            obj.insert("role".into(), Value::String(msg.role.clone()));

            // Text only — images were refused above.
            obj.insert("content".into(), Value::String(msg.content.clone()));

            // Assistant message with tool_calls: stringify arguments, remember
            // the ids so the subsequent tool messages can reference them.
            if let Some(tcs) = &msg.tool_calls
                && msg.role == "assistant"
            {
                let converted: Vec<Value> = tcs
                    .iter()
                    .enumerate()
                    .map(|(i, call)| {
                        let id = call.id.clone().unwrap_or_else(|| format!("call_{}", i));
                        let args_str = serde_json::to_string(&call.function.arguments)
                            .unwrap_or_else(|_| "{}".to_string());
                        json!({
                            "id": id,
                            "type": "function",
                            "function": {
                                "name": call.function.name,
                                "arguments": args_str,
                            }
                        })
                    })
                    .collect();
                last_tool_call_ids = converted
                    .iter()
                    .filter_map(|v| v.get("id").and_then(|x| x.as_str()).map(String::from))
                    .collect();
                next_tool_result_idx = 0;
                obj.insert("tool_calls".into(), Value::Array(converted));
            }

            // Tool result messages: attach tool_call_id from the last assistant turn.
            if msg.role == "tool" {
                let id = last_tool_call_ids
                    .get(next_tool_result_idx)
                    .cloned()
                    .unwrap_or_else(|| "call_0".to_string());
                obj.insert("tool_call_id".into(), Value::String(id));
                next_tool_result_idx += 1;
            }

            out.push(Value::Object(obj));
        }

        Ok(out)
    }

    /// Parse an OpenAI-compatible assistant message back into canonical shape.
    fn openai_message_to_chat(msg: &Value) -> Result<ChatMessage> {
        let obj = msg
            .as_object()
            .ok_or_else(|| anyhow!("response message is not an object"))?;
        let role = obj
            .get("role")
            .and_then(|v| v.as_str())
            .unwrap_or("assistant")
            .to_string();
        let content = obj
            .get("content")
            .and_then(|v| v.as_str())
            .unwrap_or("")
            .to_string();

        let tool_calls = if let Some(tcs) = obj.get("tool_calls").and_then(|v| v.as_array()) {
            let mut parsed = Vec::with_capacity(tcs.len());
            for tc in tcs {
                let id = tc.get("id").and_then(|v| v.as_str()).map(String::from);
                let function = tc
                    .get("function")
                    .ok_or_else(|| anyhow!("tool_call missing function field"))?;
                let name = function
                    .get("name")
                    .and_then(|v| v.as_str())
                    .unwrap_or_default()
                    .to_string();
                let args_value = match function.get("arguments") {
                    // OpenAI-compat: stringified JSON.
                    Some(Value::String(s)) => {
                        serde_json::from_str::<Value>(s).unwrap_or_else(|_| json!({}))
                    }
                    // Some providers emit arguments as an object directly — accept both.
                    Some(v @ Value::Object(_)) => v.clone(),
                    _ => json!({}),
                };
                parsed.push(ToolCall {
                    id,
                    function: ToolCallFunction {
                        name,
                        arguments: args_value,
                    },
                });
            }
            Some(parsed)
        } else {
            None
        };

        Ok(ChatMessage {
            role,
            content,
            tool_calls,
            images: None,
        })
    }

    fn build_options(&self) -> Vec<(&'static str, Value)> {
        let mut v = Vec::new();
        if let Some(t) = self.temperature {
            v.push(("temperature", json!(t)));
        }
        if let Some(p) = self.top_p {
            v.push(("top_p", json!(p)));
        }
        if let Some(k) = self.top_k {
            v.push(("top_k", json!(k)));
        }
        if let Some(m) = self.min_p {
            v.push(("min_p", json!(m)));
        }
        if let Some(c) = self.num_ctx {
            // OpenAI uses max_tokens for generation bound; num_ctx isn't
            // directly transferable. Skip rather than silently mis-map.
            let _ = c;
        }
        if let Some(m) = self.max_tokens {
            v.push(("max_tokens", json!(m)));
        }
        v
    }
}

#[async_trait]
impl LlmClient for OpenRouterClient {
    async fn generate(
        &self,
        prompt: &str,
        system: Option<&str>,
        images: Option<Vec<String>>,
    ) -> Result<String> {
        let mut messages: Vec<ChatMessage> = Vec::new();
        if let Some(sys) = system {
            messages.push(ChatMessage::system(sys));
        }
        let mut user = ChatMessage::user(prompt);
        user.images = images;
        messages.push(user);

        // Delegates to chat_with_tools, which starts the llm.request span
        // (operation=chat) — one span per HTTP request.
        let (reply, _, _) = self.chat_with_tools(messages, Vec::new()).await?;
        Ok(reply.content)
    }

    async fn chat_with_tools(
        &self,
        messages: Vec<ChatMessage>,
        tools: Vec<Tool>,
    ) -> Result<(ChatMessage, Option<i32>, Option<i32>)> {
        let span = self.start_request_span("chat", &self.primary_model);
        self.chat_with_tools_impl(Some(&span), messages, tools)
            .await
    }

    async fn chat_with_tools_stream(
        &self,
        messages: Vec<ChatMessage>,
        tools: Vec<Tool>,
    ) -> Result<BoxStream<'static, Result<LlmStreamEvent>>> {
        // The span outlives this method — the stream yields until the
        // response fully drains, so the owned span moves into the
        // generator and is finalized there.
        let span = self.start_request_span("chat_stream", &self.primary_model);

        let url = format!("{}/chat/completions", self.base_url);
        let mut body = serde_json::Map::new();
        body.insert("model".into(), Value::String(self.primary_model.clone()));
        body.insert(
            "messages".into(),
            Value::Array(Self::messages_to_openai(&messages)?),
        );
        body.insert("stream".into(), Value::Bool(true));
        // Ask for usage data in the final chunk (OpenAI + OpenRouter
        // both honor this options bag).
        body.insert(
            "stream_options".into(),
            serde_json::json!({ "include_usage": true }),
        );
        if !tools.is_empty() {
            body.insert(
                "tools".into(),
                serde_json::to_value(&tools).context("serializing tools")?,
            );
        }
        for (k, v) in self.build_options() {
            body.insert(k.into(), v);
        }

        let mut request = self
            .authed(self.client.post(&url))
            .json(&Value::Object(body));
        request = crate::otel::with_traceparent(request, &span);
        let resp = request
            .send()
            .await
            .with_context(|| format!("POST {} failed", url))?;

        if !resp.status().is_success() {
            let status = resp.status();
            crate::otel::record_http_failure(
                Some(&span),
                status.as_u16(),
                &format!("OpenRouter stream request failed: {status}"),
            );
            let body = resp.text().await.unwrap_or_default();
            bail!("OpenRouter stream request failed: {} — {}", status, body);
        }
        crate::otel::set_http_status(Some(&span), resp.status().as_u16());

        // OpenAI-compat SSE stream. Each event is `data: <json>\n\n`, with
        // `data: [DONE]` signalling completion. Tool calls arrive as
        // `delta.tool_calls[i]` chunks that must be concatenated by index.
        let byte_stream = resp.bytes_stream();
        let stream = async_stream::stream! {
            let mut byte_stream = byte_stream;
            let mut buf: Vec<u8> = Vec::new();
            let mut accumulated_content = String::new();
            // tool call state: index -> (id, name, args_string)
            let mut tool_state: std::collections::BTreeMap<
                usize,
                (Option<String>, Option<String>, String),
            > = std::collections::BTreeMap::new();
            let mut role = "assistant".to_string();
            let mut prompt_tokens: Option<i32> = None;
            let mut completion_tokens: Option<i32> = None;
            let mut done_seen = false;

            while let Some(chunk) = byte_stream.next().await {
                let chunk = match chunk {
                    Ok(b) => b,
                    Err(e) => {
                        span.set_status(Status::error(format!("stream read failed: {e}")));
                        yield Err(anyhow!("stream read failed: {}", e));
                        return;
                    }
                };
                buf.extend_from_slice(&chunk);

                // SSE frames are delimited by a blank line. Walk the buffer
                // for "\n\n" markers; anything before them is a complete
                // frame (possibly multi-line).
                while let Some(sep) = find_double_newline(&buf) {
                    let frame = buf.drain(..sep + 2).collect::<Vec<_>>();
                    let frame_str = match std::str::from_utf8(&frame) {
                        Ok(s) => s,
                        Err(_) => continue,
                    };
                    // A frame is one or more lines; the payload is on data:
                    // lines. Ignore comments and other fields.
                    for line in frame_str.lines() {
                        let line = line.trim_end_matches('\r');
                        let payload = match line.strip_prefix("data: ") {
                            Some(p) => p,
                            None => continue,
                        };
                        if payload == "[DONE]" {
                            done_seen = true;
                            break;
                        }
                        let v: Value = match serde_json::from_str(payload) {
                            Ok(v) => v,
                            Err(e) => {
                                log::warn!(
                                    "malformed OpenRouter SSE frame: {} ({})",
                                    payload,
                                    e
                                );
                                continue;
                            }
                        };

                        // Usage can arrive in a dedicated final frame with
                        // empty choices.
                        if let Some(usage) = v.get("usage") {
                            prompt_tokens = usage
                                .get("prompt_tokens")
                                .and_then(|n| n.as_i64())
                                .map(|n| n as i32);
                            completion_tokens = usage
                                .get("completion_tokens")
                                .and_then(|n| n.as_i64())
                                .map(|n| n as i32);
                            if let Some(cost) = usage.get("cost").and_then(|c| c.as_f64()) {
                                span.set_attribute("llm.cost_usd", cost);
                            }
                        }

                        let Some(choices) = v.get("choices").and_then(|c| c.as_array())
                        else {
                            continue;
                        };
                        let Some(choice) = choices.first() else { continue };
                        let delta = match choice.get("delta") {
                            Some(d) => d,
                            None => continue,
                        };
                        if let Some(r) = delta.get("role").and_then(|v| v.as_str()) {
                            role = r.to_string();
                        }
                        if let Some(content) =
                            delta.get("content").and_then(|v| v.as_str())
                            && !content.is_empty()
                        {
                            accumulated_content.push_str(content);
                            yield Ok(LlmStreamEvent::TextDelta(content.to_string()));
                        }
                        if let Some(tcs) = delta.get("tool_calls").and_then(|v| v.as_array()) {
                            for tc_delta in tcs {
                                let idx = tc_delta
                                    .get("index")
                                    .and_then(|n| n.as_u64())
                                    .unwrap_or(0) as usize;
                                let entry = tool_state
                                    .entry(idx)
                                    .or_insert((None, None, String::new()));
                                if let Some(id) =
                                    tc_delta.get("id").and_then(|v| v.as_str())
                                {
                                    entry.0 = Some(id.to_string());
                                }
                                if let Some(func) = tc_delta.get("function") {
                                    if let Some(name) =
                                        func.get("name").and_then(|v| v.as_str())
                                    {
                                        entry.1 = Some(name.to_string());
                                    }
                                    if let Some(args) =
                                        func.get("arguments").and_then(|v| v.as_str())
                                    {
                                        entry.2.push_str(args);
                                    }
                                }
                            }
                        }
                    }
                    if done_seen {
                        break;
                    }
                }
                if done_seen {
                    break;
                }
            }

            // Finalize tool calls: parse accumulated argument strings.
            let tool_calls: Option<Vec<ToolCall>> = if tool_state.is_empty() {
                None
            } else {
                let mut v = Vec::with_capacity(tool_state.len());
                for (_idx, (id, name, args)) in tool_state {
                    let arguments: Value = if args.trim().is_empty() {
                        Value::Object(Default::default())
                    } else {
                        serde_json::from_str(&args).unwrap_or_else(|_| {
                            Value::Object(Default::default())
                        })
                    };
                    v.push(ToolCall {
                        id,
                        function: ToolCallFunction {
                            name: name.unwrap_or_default(),
                            arguments,
                        },
                    });
                }
                Some(v)
            };

            let message = ChatMessage {
                role,
                content: accumulated_content,
                tool_calls,
                images: None,
            };
            if let Some(pt) = prompt_tokens {
                span.set_attribute("llm.tokens.input", pt as i64);
            }
            if let Some(ct) = completion_tokens {
                span.set_attribute("llm.tokens.output", ct as i64);
            }
            span.set_status(Status::Ok);
            yield Ok(LlmStreamEvent::Done {
                message,
                prompt_eval_count: prompt_tokens,
                eval_count: completion_tokens,
            });
        };

        Ok(Box::pin(stream))
    }

    async fn generate_embeddings(&self, texts: &[&str]) -> Result<Vec<Vec<f32>>> {
        let span = self.start_request_span("embeddings", &self.embedding_model);
        let url = format!("{}/embeddings", self.base_url);
        let body = json!({
            "model": self.embedding_model,
            "input": texts,
        });

        let mut request = self.authed(self.client.post(&url)).json(&body);
        request = crate::otel::with_traceparent(request, &span);
        let resp = request
            .send()
            .await
            .with_context(|| format!("POST {} failed", url))
            .inspect_err(|_| {
                span.set_status(Status::error("OpenRouter embedding request failed"));
            })?;

        if !resp.status().is_success() {
            let status = resp.status();
            crate::otel::record_http_failure(
                Some(&span),
                status.as_u16(),
                &format!("OpenRouter embedding request failed: {status}"),
            );
            let body = resp.text().await.unwrap_or_default();
            bail!("OpenRouter embedding request failed: {} — {}", status, body);
        }
        crate::otel::set_http_status(Some(&span), resp.status().as_u16());

        #[derive(Deserialize)]
        struct EmbedResponse {
            data: Vec<EmbedItem>,
        }
        #[derive(Deserialize)]
        struct EmbedItem {
            embedding: Vec<f32>,
        }

        let parsed: EmbedResponse = resp.json().await.context("parsing embed response")?;
        span.set_status(Status::Ok);
        Ok(parsed.data.into_iter().map(|i| i.embedding).collect())
    }

    async fn describe_image(&self, _image_base64: &str) -> Result<String> {
        // Describing an image means uploading it. Hybrid mode always
        // describes on the local backend (`ResolvedBackend::local`), so this
        // is never the intended path — refuse loudly if something reaches it.
        log::error!("{IMAGES_STAY_LOCAL}");
        bail!(IMAGES_STAY_LOCAL)
    }

    async fn list_models(&self) -> Result<Vec<ModelCapabilities>> {
        {
            let cache = MODEL_CAPABILITIES_CACHE.lock().unwrap();
            if let Some(entry) = cache.get(&self.base_url)
                && !entry.is_expired()
            {
                return Ok(entry.data.clone());
            }
        }

        let url = format!("{}/models", self.base_url);
        let resp = self
            .authed(self.client.get(&url))
            .send()
            .await
            .with_context(|| format!("GET {} failed", url))?;

        if !resp.status().is_success() {
            let status = resp.status();
            let body = resp.text().await.unwrap_or_default();
            bail!("OpenRouter list_models failed: {} — {}", status, body);
        }

        let parsed: Value = resp.json().await.context("parsing models response")?;
        let data = parsed
            .get("data")
            .and_then(|v| v.as_array())
            .ok_or_else(|| anyhow!("models response missing data[]"))?;

        let caps: Vec<ModelCapabilities> = data.iter().map(parse_model_capabilities).collect();

        {
            let mut cache = MODEL_CAPABILITIES_CACHE.lock().unwrap();
            cache.insert(self.base_url.clone(), CachedEntry::new(caps.clone()));
        }

        Ok(caps)
    }

    async fn model_capabilities(&self, model: &str) -> Result<ModelCapabilities> {
        let all = self.list_models().await?;
        all.into_iter()
            .find(|m| m.name == model)
            .ok_or_else(|| anyhow!("model '{}' not found on OpenRouter", model))
    }

    fn primary_model(&self) -> &str {
        &self.primary_model
    }
}

impl OpenRouterClient {
    /// HTTP core of `chat_with_tools`. `span` is the `llm.request` span
    /// started by the caller (or a funnelling entry point like
    /// `describe_image`) so attributes from the response land on the right
    /// operation label.
    async fn chat_with_tools_impl(
        &self,
        span: Option<&tracing::Span>,
        messages: Vec<ChatMessage>,
        tools: Vec<Tool>,
    ) -> Result<(ChatMessage, Option<i32>, Option<i32>)> {
        let url = format!("{}/chat/completions", self.base_url);
        let mut body = serde_json::Map::new();
        body.insert("model".into(), Value::String(self.primary_model.clone()));
        body.insert(
            "messages".into(),
            Value::Array(Self::messages_to_openai(&messages)?),
        );
        body.insert("stream".into(), Value::Bool(false));
        if !tools.is_empty() {
            body.insert(
                "tools".into(),
                serde_json::to_value(&tools).context("serializing tools")?,
            );
        }
        for (k, v) in self.build_options() {
            body.insert(k.into(), v);
        }

        log::info!(
            "OpenRouter chat_with_tools: model={} messages={} tools={}",
            self.primary_model,
            messages.len(),
            tools.len()
        );

        let mut request = self
            .authed(self.client.post(&url))
            .json(&Value::Object(body));
        if let Some(s) = span {
            request = crate::otel::with_traceparent(request, s);
        }
        let resp = match request.send().await {
            Ok(r) => r,
            Err(e) => {
                if let Some(s) = span {
                    s.set_status(Status::error("OpenRouter request failed"));
                }
                return Err(e).with_context(|| format!("POST {} failed", url));
            }
        };

        if !resp.status().is_success() {
            let status = resp.status();
            crate::otel::record_http_failure(
                span,
                status.as_u16(),
                &format!("OpenRouter chat request failed: {status}"),
            );
            let body = resp.text().await.unwrap_or_default();
            bail!("OpenRouter chat request failed: {} — {}", status, body);
        }
        crate::otel::set_http_status(span, resp.status().as_u16());

        let parsed: Value = match resp.json().await {
            Ok(v) => v,
            Err(e) => {
                if let Some(s) = span {
                    s.set_status(Status::error("parsing chat response failed"));
                }
                return Err(e).context("parsing chat response");
            }
        };
        let choice = parsed
            .get("choices")
            .and_then(|v| v.as_array())
            .and_then(|a| a.first())
            .ok_or_else(|| {
                anyhow!(
                    "response missing choices[0]: {}",
                    extract_openrouter_error_detail(&parsed)
                )
            })?;
        let msg = choice.get("message").ok_or_else(|| {
            anyhow!(
                "choices[0] missing message: {}",
                extract_openrouter_error_detail(&parsed)
            )
        })?;
        let chat_msg = Self::openai_message_to_chat(msg)?;

        let usage = parsed.get("usage");
        let prompt_tokens = usage
            .and_then(|u| u.get("prompt_tokens"))
            .and_then(|v| v.as_i64())
            .map(|n| n as i32);
        let completion_tokens = usage
            .and_then(|u| u.get("completion_tokens"))
            .and_then(|v| v.as_i64())
            .map(|n| n as i32);
        // OpenRouter reports per-request USD cost in `usage.cost`.
        if let Some(s) = span {
            if let Some(pt) = prompt_tokens {
                s.set_attribute("llm.tokens.input", pt as i64);
            }
            if let Some(ct) = completion_tokens {
                s.set_attribute("llm.tokens.output", ct as i64);
            }
            if let Some(cost) = usage.and_then(|u| u.get("cost")).and_then(|c| c.as_f64()) {
                s.set_attribute("llm.cost_usd", cost);
            }
            s.set_status(Status::Ok);
        }

        Ok((chat_msg, prompt_tokens, completion_tokens))
    }
}

/// Extract a diagnostic fragment from an OpenRouter response body that
/// doesn't match the expected `{choices: [...]}` shape. OpenRouter will
/// sometimes return 200 OK with `{"error": {"message": "...", "code": ...}}`
/// when the upstream provider (Anthropic/OpenAI/Google/etc) errored out
/// — rate limits, content moderation, model overload, provider timeout.
/// Surface the structured error if present; otherwise fall back to a
/// truncated raw-JSON view so the log line is actionable.
fn extract_openrouter_error_detail(parsed: &Value) -> String {
    if let Some(err) = parsed.get("error") {
        let message = err
            .get("message")
            .and_then(|v| v.as_str())
            .unwrap_or("(no message)");
        let code = err
            .get("code")
            .map(|v| match v {
                Value::String(s) => s.clone(),
                other => other.to_string(),
            })
            .unwrap_or_else(|| "?".to_string());
        let short_message: String = message.chars().take(240).collect();
        return format!("error code={} message=\"{}\"", code, short_message);
    }
    let raw = parsed.to_string();
    raw.chars().take(300).collect()
}

/// Find the byte offset of the first `\n\n` (end of an SSE frame) in `buf`.
/// Returns the index of the first `\n` of the pair, so the full separator is
/// `buf[idx..=idx+1]`. Also handles `\r\n\r\n` since some servers emit it.
fn find_double_newline(buf: &[u8]) -> Option<usize> {
    for i in 0..buf.len().saturating_sub(1) {
        if buf[i] == b'\n' && buf[i + 1] == b'\n' {
            return Some(i);
        }
        // \r\n\r\n: the second \n of this pattern is at i+2; flag at i so the
        // drain call (which consumes ..sep+2) takes exactly the frame.
        if i + 3 < buf.len()
            && buf[i] == b'\r'
            && buf[i + 1] == b'\n'
            && buf[i + 2] == b'\r'
            && buf[i + 3] == b'\n'
        {
            return Some(i + 1);
        }
    }
    None
}

fn parse_model_capabilities(m: &Value) -> ModelCapabilities {
    let name = m
        .get("id")
        .and_then(|v| v.as_str())
        .unwrap_or_default()
        .to_string();
    let has_tool_calling = m
        .get("supported_parameters")
        .and_then(|v| v.as_array())
        .map(|arr| arr.iter().any(|x| x.as_str() == Some("tools")))
        .unwrap_or(false);
    let has_vision = m
        .get("architecture")
        .and_then(|v| v.get("input_modalities"))
        .and_then(|v| v.as_array())
        .map(|arr| arr.iter().any(|x| x.as_str() == Some("image")))
        .unwrap_or(false);
    ModelCapabilities {
        name,
        has_vision,
        has_tool_calling,
        context_window: None,
    }
}

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

    #[test]
    fn tool_call_arguments_stringified_on_send() {
        let mut msg = ChatMessage {
            role: "assistant".into(),
            content: String::new(),
            tool_calls: Some(vec![ToolCall {
                id: Some("call_abc".into()),
                function: ToolCallFunction {
                    name: "search_sms".into(),
                    arguments: json!({"query": "hello", "limit": 5}),
                },
            }]),
            images: None,
        };
        msg.tool_calls.as_mut().unwrap()[0].function.arguments =
            json!({"query": "hello", "limit": 5});

        let wire = OpenRouterClient::messages_to_openai(&[msg]).unwrap();
        let tcs = wire[0]
            .get("tool_calls")
            .and_then(|v| v.as_array())
            .expect("tool_calls present");
        let args = tcs[0]
            .get("function")
            .and_then(|f| f.get("arguments"))
            .and_then(|a| a.as_str())
            .expect("arguments stringified");
        let parsed: Value = serde_json::from_str(args).unwrap();
        assert_eq!(parsed["query"], "hello");
        assert_eq!(parsed["limit"], 5);
    }

    #[test]
    fn tool_call_arguments_parsed_on_receive() {
        let response_msg = json!({
            "role": "assistant",
            "content": "",
            "tool_calls": [{
                "id": "call_xyz",
                "type": "function",
                "function": {
                    "name": "get_weather",
                    "arguments": "{\"city\":\"Boston\",\"units\":\"celsius\"}"
                }
            }]
        });

        let parsed = OpenRouterClient::openai_message_to_chat(&response_msg).unwrap();
        let tcs = parsed.tool_calls.unwrap();
        assert_eq!(tcs.len(), 1);
        assert_eq!(tcs[0].function.name, "get_weather");
        assert_eq!(tcs[0].function.arguments["city"], "Boston");
        assert_eq!(tcs[0].function.arguments["units"], "celsius");
        assert_eq!(tcs[0].id.as_deref(), Some("call_xyz"));
    }

    #[test]
    fn tool_call_arguments_accept_native_json_on_receive() {
        // Some providers return arguments as an object directly; accept both.
        let response_msg = json!({
            "role": "assistant",
            "content": "",
            "tool_calls": [{
                "id": "call_1",
                "type": "function",
                "function": {
                    "name": "foo",
                    "arguments": {"nested": {"k": 1}}
                }
            }]
        });
        let parsed = OpenRouterClient::openai_message_to_chat(&response_msg).unwrap();
        let tc = &parsed.tool_calls.unwrap()[0];
        assert_eq!(tc.function.arguments["nested"]["k"], 1);
    }

    #[test]
    fn any_image_anywhere_in_the_transcript_is_refused() {
        // Not just the latest message: a replayed transcript whose first
        // user turn still holds the photo must be refused too.
        let mut first = ChatMessage::user("What is in this photo?");
        first.images = Some(vec!["BASE64DATA".into()]);
        let later = ChatMessage::user("and then?");
        let err = OpenRouterClient::messages_to_openai(&[first, later]).unwrap_err();
        assert!(err.to_string().contains("photos stay on the local network"));
    }

    #[test]
    fn an_empty_image_list_is_not_an_image() {
        let mut msg = ChatMessage::user("hi");
        msg.images = Some(Vec::new());
        assert!(OpenRouterClient::messages_to_openai(&[msg]).is_ok());
    }

    #[tokio::test]
    async fn describe_image_refuses_without_a_network_call() {
        // Points at a closed port: if the guard ever stopped refusing, this
        // would fail with a connection error instead of the guard's.
        let client =
            OpenRouterClient::new("key".into(), Some("http://127.0.0.1:9".into()), "m".into());
        let err = client.describe_image("BASE64DATA").await.unwrap_err();
        assert!(err.to_string().contains("photos stay on the local network"));
    }

    #[test]
    fn text_only_message_stays_string() {
        let msg = ChatMessage::user("hello");
        let wire = OpenRouterClient::messages_to_openai(&[msg]).unwrap();
        assert_eq!(wire[0]["content"], "hello");
        assert!(wire[0]["content"].as_str().is_some());
    }

    #[test]
    fn tool_result_inherits_tool_call_id_from_prior_assistant() {
        let assistant = ChatMessage {
            role: "assistant".into(),
            content: String::new(),
            tool_calls: Some(vec![ToolCall {
                id: Some("call_42".into()),
                function: ToolCallFunction {
                    name: "lookup".into(),
                    arguments: json!({}),
                },
            }]),
            images: None,
        };
        let tool_result = ChatMessage::tool_result("found it");

        let wire = OpenRouterClient::messages_to_openai(&[assistant, tool_result]).unwrap();
        assert_eq!(wire[1]["role"], "tool");
        assert_eq!(wire[1]["tool_call_id"], "call_42");
    }

    #[test]
    fn multiple_tool_results_map_to_sequential_call_ids() {
        let assistant = ChatMessage {
            role: "assistant".into(),
            content: String::new(),
            tool_calls: Some(vec![
                ToolCall {
                    id: Some("call_A".into()),
                    function: ToolCallFunction {
                        name: "a".into(),
                        arguments: json!({}),
                    },
                },
                ToolCall {
                    id: Some("call_B".into()),
                    function: ToolCallFunction {
                        name: "b".into(),
                        arguments: json!({}),
                    },
                },
            ]),
            images: None,
        };
        let r1 = ChatMessage::tool_result("a result");
        let r2 = ChatMessage::tool_result("b result");

        let wire = OpenRouterClient::messages_to_openai(&[assistant, r1, r2]).unwrap();
        assert_eq!(wire[1]["tool_call_id"], "call_A");
        assert_eq!(wire[2]["tool_call_id"], "call_B");
    }

    #[test]
    fn missing_tool_call_id_gets_synthetic_fallback() {
        let assistant = ChatMessage {
            role: "assistant".into(),
            content: String::new(),
            tool_calls: Some(vec![ToolCall {
                id: None,
                function: ToolCallFunction {
                    name: "noid".into(),
                    arguments: json!({}),
                },
            }]),
            images: None,
        };
        let wire = OpenRouterClient::messages_to_openai(&[assistant]).unwrap();
        let tcs = wire[0]
            .get("tool_calls")
            .and_then(|v| v.as_array())
            .unwrap();
        assert_eq!(tcs[0]["id"], "call_0");
    }

    #[test]
    fn parse_model_capabilities_extracts_tools_and_vision() {
        let m = json!({
            "id": "anthropic/claude-sonnet-4",
            "supported_parameters": ["temperature", "top_p", "tools", "max_tokens"],
            "architecture": {
                "input_modalities": ["text", "image"]
            }
        });
        let caps = parse_model_capabilities(&m);
        assert_eq!(caps.name, "anthropic/claude-sonnet-4");
        assert!(caps.has_tool_calling);
        assert!(caps.has_vision);
    }

    #[test]
    fn parse_model_capabilities_handles_missing_fields() {
        let m = json!({
            "id": "some/text-only-model"
        });
        let caps = parse_model_capabilities(&m);
        assert_eq!(caps.name, "some/text-only-model");
        assert!(!caps.has_tool_calling);
        assert!(!caps.has_vision);
    }
}