use crate::providers::traits::{ChatMessage, ChatResponse, Provider};
use async_trait::async_trait;
use reqwest::Client;
use serde::{Deserialize, Serialize};

pub struct OpenRouterProvider {
    api_key: Option<String>,
    client: Client,
}

#[derive(Debug, Serialize)]
struct ChatRequest {
    model: String,
    messages: Vec<Message>,
    temperature: f64,
}

#[derive(Debug, Serialize)]
struct Message {
    role: String,
    content: String,
}

#[derive(Debug, Deserialize)]
struct ApiChatResponse {
    choices: Vec<Choice>,
}

#[derive(Debug, Deserialize)]
struct Choice {
    message: ResponseMessage,
}

#[derive(Debug, Deserialize)]
struct ResponseMessage {
    content: String,
}

impl OpenRouterProvider {
    pub fn new(api_key: Option<&str>) -> Self {
        Self {
            api_key: api_key.map(ToString::to_string),
            client: Client::builder()
                .timeout(std::time::Duration::from_secs(120))
                .connect_timeout(std::time::Duration::from_secs(10))
                .build()
                .unwrap_or_else(|_| Client::new()),
        }
    }
}

#[async_trait]
impl Provider for OpenRouterProvider {
    async fn warmup(&self) -> anyhow::Result<()> {
        // Hit a lightweight endpoint to establish TLS + HTTP/2 connection pool.
        // This prevents the first real chat request from timing out on cold start.
        if let Some(api_key) = self.api_key.as_ref() {
            self.client
                .get("https://openrouter.ai/api/v1/auth/key")
                .header("Authorization", format!("Bearer {api_key}"))
                .send()
                .await?
                .error_for_status()?;
        }
        Ok(())
    }

    async fn chat_with_system(
        &self,
        system_prompt: Option<&str>,
        message: &str,
        model: &str,
        temperature: f64,
    ) -> anyhow::Result<ChatResponse> {
        let api_key = self.api_key.as_ref()
            .ok_or_else(|| anyhow::anyhow!("OpenRouter API key not set. Run `zeroclaw onboard` or set OPENROUTER_API_KEY env var."))?;

        let mut messages = Vec::new();

        if let Some(sys) = system_prompt {
            messages.push(Message {
                role: "system".to_string(),
                content: sys.to_string(),
            });
        }

        messages.push(Message {
            role: "user".to_string(),
            content: message.to_string(),
        });

        let request = ChatRequest {
            model: model.to_string(),
            messages,
            temperature,
        };

        let response = self
            .client
            .post("https://openrouter.ai/api/v1/chat/completions")
            .header("Authorization", format!("Bearer {api_key}"))
            .header(
                "HTTP-Referer",
                "https://github.com/theonlyhennygod/zeroclaw",
            )
            .header("X-Title", "ZeroClaw")
            .json(&request)
            .send()
            .await?;

        if !response.status().is_success() {
            return Err(super::api_error("OpenRouter", response).await);
        }

        let chat_response: ApiChatResponse = response.json().await?;

        chat_response
            .choices
            .into_iter()
            .next()
            .map(|c| ChatResponse::with_text(c.message.content))
            .ok_or_else(|| anyhow::anyhow!("No response from OpenRouter"))
    }

    async fn chat_with_history(
        &self,
        messages: &[ChatMessage],
        model: &str,
        temperature: f64,
    ) -> anyhow::Result<ChatResponse> {
        let api_key = self.api_key.as_ref()
            .ok_or_else(|| anyhow::anyhow!("OpenRouter API key not set. Run `zeroclaw onboard` or set OPENROUTER_API_KEY env var."))?;

        let api_messages: Vec<Message> = messages
            .iter()
            .map(|m| Message {
                role: m.role.clone(),
                content: m.content.clone(),
            })
            .collect();

        let request = ChatRequest {
            model: model.to_string(),
            messages: api_messages,
            temperature,
        };

        let response = self
            .client
            .post("https://openrouter.ai/api/v1/chat/completions")
            .header("Authorization", format!("Bearer {api_key}"))
            .header(
                "HTTP-Referer",
                "https://github.com/theonlyhennygod/zeroclaw",
            )
            .header("X-Title", "ZeroClaw")
            .json(&request)
            .send()
            .await?;

        if !response.status().is_success() {
            return Err(super::api_error("OpenRouter", response).await);
        }

        let chat_response: ApiChatResponse = response.json().await?;

        chat_response
            .choices
            .into_iter()
            .next()
            .map(|c| ChatResponse::with_text(c.message.content))
            .ok_or_else(|| anyhow::anyhow!("No response from OpenRouter"))
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::providers::traits::{ChatMessage, Provider};

    #[test]
    fn creates_with_key() {
        let provider = OpenRouterProvider::new(Some("sk-or-123"));
        assert_eq!(provider.api_key.as_deref(), Some("sk-or-123"));
    }

    #[test]
    fn creates_without_key() {
        let provider = OpenRouterProvider::new(None);
        assert!(provider.api_key.is_none());
    }

    #[tokio::test]
    async fn warmup_without_key_is_noop() {
        let provider = OpenRouterProvider::new(None);
        let result = provider.warmup().await;
        assert!(result.is_ok());
    }

    #[tokio::test]
    async fn chat_with_system_fails_without_key() {
        let provider = OpenRouterProvider::new(None);
        let result = provider
            .chat_with_system(Some("system"), "hello", "openai/gpt-4o", 0.2)
            .await;

        assert!(result.is_err());
        assert!(result.unwrap_err().to_string().contains("API key not set"));
    }

    #[tokio::test]
    async fn chat_with_history_fails_without_key() {
        let provider = OpenRouterProvider::new(None);
        let messages = vec![
            ChatMessage {
                role: "system".into(),
                content: "be concise".into(),
            },
            ChatMessage {
                role: "user".into(),
                content: "hello".into(),
            },
        ];

        let result = provider
            .chat_with_history(&messages, "anthropic/claude-sonnet-4", 0.7)
            .await;

        assert!(result.is_err());
        assert!(result.unwrap_err().to_string().contains("API key not set"));
    }

    #[test]
    fn chat_request_serializes_with_system_and_user() {
        let request = ChatRequest {
            model: "anthropic/claude-sonnet-4".into(),
            messages: vec![
                Message {
                    role: "system".into(),
                    content: "You are helpful".into(),
                },
                Message {
                    role: "user".into(),
                    content: "Summarize this".into(),
                },
            ],
            temperature: 0.5,
        };

        let json = serde_json::to_string(&request).unwrap();

        assert!(json.contains("anthropic/claude-sonnet-4"));
        assert!(json.contains("\"role\":\"system\""));
        assert!(json.contains("\"role\":\"user\""));
        assert!(json.contains("\"temperature\":0.5"));
    }

    #[test]
    fn chat_request_serializes_history_messages() {
        let messages = [
            ChatMessage {
                role: "assistant".into(),
                content: "Previous answer".into(),
            },
            ChatMessage {
                role: "user".into(),
                content: "Follow-up".into(),
            },
        ];

        let request = ChatRequest {
            model: "google/gemini-2.5-pro".into(),
            messages: messages
                .iter()
                .map(|msg| Message {
                    role: msg.role.clone(),
                    content: msg.content.clone(),
                })
                .collect(),
            temperature: 0.0,
        };

        let json = serde_json::to_string(&request).unwrap();
        assert!(json.contains("\"role\":\"assistant\""));
        assert!(json.contains("\"role\":\"user\""));
        assert!(json.contains("google/gemini-2.5-pro"));
    }

    #[test]
    fn response_deserializes_single_choice() {
        let json = r#"{"choices":[{"message":{"content":"Hi from OpenRouter"}}]}"#;

        let response: ApiChatResponse = serde_json::from_str(json).unwrap();

        assert_eq!(response.choices.len(), 1);
        assert_eq!(response.choices[0].message.content, "Hi from OpenRouter");
    }

    #[test]
    fn response_deserializes_empty_choices() {
        let json = r#"{"choices":[]}"#;

        let response: ApiChatResponse = serde_json::from_str(json).unwrap();

        assert!(response.choices.is_empty());
    }
}