//! OpenAI provider. Authenticates via Bearer token.

use crate::traits::{ChatMessage, ChatRequest, ChatResponse, ModelProvider, TokenUsage, ToolCall};
use async_trait::async_trait;
use nenjo_tools::ToolSpec;
use reqwest::Client;
use serde::{Deserialize, Serialize};

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

#[derive(Debug, Serialize)]
struct NativeChatRequest {
    model: String,
    messages: Vec<NativeMessage>,
    #[serde(skip_serializing_if = "Option::is_none")]
    temperature: Option<f64>,
    #[serde(skip_serializing_if = "Option::is_none")]
    max_completion_tokens: Option<u32>,
    #[serde(skip_serializing_if = "Option::is_none")]
    tools: Option<Vec<NativeToolSpec>>,
    #[serde(skip_serializing_if = "Option::is_none")]
    tool_choice: Option<String>,
}

#[derive(Debug, Serialize)]
struct NativeMessage {
    role: String,
    #[serde(skip_serializing_if = "Option::is_none")]
    content: Option<String>,
    #[serde(skip_serializing_if = "Option::is_none")]
    tool_call_id: Option<String>,
    #[serde(skip_serializing_if = "Option::is_none")]
    tool_calls: Option<Vec<NativeToolCall>>,
}

#[derive(Debug, Serialize)]
struct NativeToolSpec {
    #[serde(rename = "type")]
    kind: String,
    function: NativeToolFunctionSpec,
}

#[derive(Debug, Serialize)]
struct NativeToolFunctionSpec {
    name: String,
    description: String,
    parameters: serde_json::Value,
}

#[derive(Debug, Serialize, Deserialize)]
struct NativeToolCall {
    #[serde(skip_serializing_if = "Option::is_none")]
    id: Option<String>,
    #[serde(rename = "type", skip_serializing_if = "Option::is_none")]
    kind: Option<String>,
    function: NativeFunctionCall,
}

#[derive(Debug, Serialize, Deserialize)]
struct NativeFunctionCall {
    name: String,
    arguments: String,
}

#[derive(Debug, Deserialize)]
struct NativeUsage {
    #[serde(default)]
    prompt_tokens: u64,
    #[serde(default)]
    completion_tokens: u64,
}

#[derive(Debug, Deserialize)]
struct NativeChatResponse {
    choices: Vec<NativeChoice>,
    #[serde(default)]
    usage: Option<NativeUsage>,
}

#[derive(Debug, Deserialize)]
struct NativeChoice {
    message: NativeResponseMessage,
}

#[derive(Debug, Deserialize)]
struct NativeResponseMessage {
    #[serde(default)]
    content: Option<String>,
    #[serde(default)]
    tool_calls: Option<Vec<NativeToolCall>>,
}

impl OpenAiProvider {
    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()),
        }
    }

    fn is_reasoning_model(model: &str) -> bool {
        let m = model.to_lowercase();
        m.starts_with("o1") || m.starts_with("o3") || m.starts_with("o4")
    }

    fn convert_tools(tools: Option<&[ToolSpec]>) -> Option<Vec<NativeToolSpec>> {
        tools.map(|items| {
            items
                .iter()
                .map(|tool| NativeToolSpec {
                    kind: "function".to_string(),
                    function: NativeToolFunctionSpec {
                        name: crate::sanitize_tool_name(&tool.name),
                        description: tool.description.clone(),
                        parameters: tool.parameters.clone(),
                    },
                })
                .collect()
        })
    }

    fn convert_messages(messages: &[ChatMessage]) -> Vec<NativeMessage> {
        messages
            .iter()
            .map(|m| {
                if m.role == "assistant"
                    && let Ok(value) = serde_json::from_str::<serde_json::Value>(&m.content)
                    && let Some(tool_calls_value) = value.get("tool_calls")
                    && let Ok(parsed_calls) =
                        serde_json::from_value::<Vec<ToolCall>>(tool_calls_value.clone())
                {
                    let tool_calls = parsed_calls
                        .into_iter()
                        .map(|tc| NativeToolCall {
                            id: Some(tc.id),
                            kind: Some("function".to_string()),
                            function: NativeFunctionCall {
                                name: tc.name,
                                arguments: tc.arguments,
                            },
                        })
                        .collect::<Vec<_>>();
                    let content = value
                        .get("content")
                        .and_then(serde_json::Value::as_str)
                        .map(ToString::to_string);
                    return NativeMessage {
                        role: "assistant".to_string(),
                        content,
                        tool_call_id: None,
                        tool_calls: Some(tool_calls),
                    };
                }

                if m.role == "tool"
                    && let Ok(value) = serde_json::from_str::<serde_json::Value>(&m.content)
                {
                    let tool_call_id = value
                        .get("tool_call_id")
                        .and_then(serde_json::Value::as_str)
                        .map(ToString::to_string);
                    let content = value
                        .get("content")
                        .and_then(serde_json::Value::as_str)
                        .map(ToString::to_string);
                    return NativeMessage {
                        role: "tool".to_string(),
                        content,
                        tool_call_id,
                        tool_calls: None,
                    };
                }

                NativeMessage {
                    role: m.role.clone(),
                    content: Some(m.content.clone()),
                    tool_call_id: None,
                    tool_calls: None,
                }
            })
            .collect()
    }

    fn parse_native_response(message: NativeResponseMessage) -> ChatResponse {
        let tool_calls = message
            .tool_calls
            .unwrap_or_default()
            .into_iter()
            .map(|tc| ToolCall {
                id: tc.id.unwrap_or_else(|| uuid::Uuid::new_v4().to_string()),
                name: tc.function.name,
                arguments: tc.function.arguments,
            })
            .collect::<Vec<_>>();

        ChatResponse {
            text: message.content,
            tool_calls,
            usage: TokenUsage::default(),
        }
    }
}

#[async_trait]
impl ModelProvider for OpenAiProvider {
    async fn chat(
        &self,
        request: ChatRequest<'_>,
        model: &str,
        temperature: f64,
    ) -> anyhow::Result<ChatResponse> {
        let api_key = self.api_key.as_ref().ok_or_else(|| {
            anyhow::anyhow!("OpenAI API key not set. Set OPENAI_API_KEY or edit config.toml.")
        })?;

        let is_reasoning = Self::is_reasoning_model(model);
        let tools = Self::convert_tools(request.tools);
        let native_request = NativeChatRequest {
            model: model.to_string(),
            messages: Self::convert_messages(request.messages),
            // Reasoning models (o1/o3/o4) require temperature=1; omit it to use the default.
            temperature: if is_reasoning {
                None
            } else {
                Some(temperature)
            },
            max_completion_tokens: Some(if is_reasoning { 65536 } else { 16384 }),
            tool_choice: tools.as_ref().map(|_| "auto".to_string()),
            tools,
        };

        let response = self
            .client
            .post("https://api.openai.com/v1/chat/completions")
            .header("Authorization", format!("Bearer {api_key}"))
            .json(&native_request)
            .send()
            .await?;

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

        let native_response: NativeChatResponse = response.json().await?;
        let usage = native_response
            .usage
            .map(|u| TokenUsage {
                input_tokens: u.prompt_tokens,
                output_tokens: u.completion_tokens,
            })
            .unwrap_or_default();
        let message = native_response
            .choices
            .into_iter()
            .next()
            .map(|c| c.message)
            .ok_or_else(|| anyhow::anyhow!("No response from OpenAI"))?;
        let mut result = Self::parse_native_response(message);
        result.usage = usage;
        Ok(result)
    }

    fn context_window(&self, model: &str) -> Option<usize> {
        let m = model.to_lowercase();
        Some(if m.contains("gpt-5") {
            // GPT-5.x: 1M
            1_000_000
        } else if m.contains("o1") || m.contains("o3") || m.contains("o4") {
            // Reasoning models: 200K
            200_000
        } else if m.contains("gpt-4o") {
            // GPT-4o / GPT-4o-mini: 128K
            128_000
        } else {
            128_000
        })
    }

    fn supports_native_tools(&self) -> bool {
        true
    }

    fn supports_developer_role(&self, model: &str) -> bool {
        Self::is_reasoning_model(model)
    }
}

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

    #[test]
    fn creates_with_key() {
        let p = OpenAiProvider::new(Some("sk-proj-abc123"));
        assert_eq!(p.api_key.as_deref(), Some("sk-proj-abc123"));
    }

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

    #[test]
    fn creates_with_empty_key() {
        let p = OpenAiProvider::new(Some(""));
        assert_eq!(p.api_key.as_deref(), Some(""));
    }

    #[tokio::test]
    async fn chat_fails_without_key() {
        let p = OpenAiProvider::new(None);
        let messages = vec![ChatMessage::user("hello")];
        let request = ChatRequest {
            messages: &messages,
            tools: None,
        };
        let result = p.chat(request, "gpt-4o", 0.7).await;
        assert!(result.is_err());
        assert!(result.unwrap_err().to_string().contains("API key not set"));
    }

    #[tokio::test]
    async fn chat_with_system_fails_without_key() {
        let p = OpenAiProvider::new(None);
        let messages = vec![
            ChatMessage::system("You are Nenjo"),
            ChatMessage::user("test"),
        ];
        let request = ChatRequest {
            messages: &messages,
            tools: None,
        };
        let result = p.chat(request, "gpt-4o", 0.5).await;
        assert!(result.is_err());
    }
}
