use crate::{
    config::ProviderConfig,
    message::{Message, Role},
    providers::{Model, Provider, ProviderError},
};
use async_trait::async_trait;
use futures::{stream::BoxStream, StreamExt};
use serde::{Deserialize, Serialize};

pub struct OpenAICompatibleProvider {
    config: ProviderConfig,
    client: reqwest::Client,
}

impl OpenAICompatibleProvider {
    pub fn new(config: ProviderConfig) -> Self {
        Self {
            config,
            client: reqwest::Client::new(),
        }
    }

    fn api_url(&self, path: &str) -> String {
        let base = self.config.base_url.trim_end_matches('/');
        format!("{}{}", base, path)
    }
}

#[async_trait]
impl Provider for OpenAICompatibleProvider {
    fn name(&self) -> &str {
        &self.config.name
    }

    fn config(&self) -> &ProviderConfig {
        &self.config
    }

    async fn list_models(&self) -> Result<Vec<Model>, ProviderError> {
        let response = self
            .client
            .get(self.api_url("/v1/models"))
            .header("Authorization", format!("Bearer {}", self.config.api_key))
            .send()
            .await?;

        if !response.status().is_success() {
            let text = response.text().await.unwrap_or_default();
            return Err(ProviderError::Api { message: text });
        }

        let data: ModelsResponse = response.json().await?;
        Ok(data
            .data
            .into_iter()
            .map(|m| Model {
                id: m.id.clone(),
                name: m.id,
            })
            .collect())
    }

    async fn chat_stream(
        &self,
        model: &str,
        messages: &[Message],
    ) -> Result<BoxStream<'_, Result<String, ProviderError>>, ProviderError> {
        let body = ChatCompletionRequest {
            model: model.to_string(),
            messages: messages.iter().map(|m| ChatMessage::from(m.clone())).collect(),
            stream: true,
        };

        let response = self
            .client
            .post(self.api_url("/v1/chat/completions"))
            .header("Authorization", format!("Bearer {}", self.config.api_key))
            .header("Content-Type", "application/json")
            .json(&body)
            .send()
            .await?;

        if !response.status().is_success() {
            let text = response.text().await.unwrap_or_default();
            return Err(ProviderError::Api { message: text });
        }

        let stream = response.bytes_stream().map(move |result| {
            result.map_err(ProviderError::Http)
        });

        let parsed = stream
            .flat_map(|result| {
                futures::stream::iter(match result {
                    Ok(bytes) => parse_sse_chunk(&bytes),
                    Err(e) => vec![Err(e)],
                })
            })
            .boxed();

        Ok(parsed)
    }
}

fn parse_sse_chunk(bytes: &[u8]) -> Vec<Result<String, ProviderError>> {
    let text = String::from_utf8_lossy(bytes);
    let mut results = Vec::new();

    for line in text.lines() {
        let line = line.trim();
        if !line.starts_with("data: ") {
            continue;
        }
        let data = &line[6..];
        if data == "[DONE]" {
            break;
        }
        match serde_json::from_str::<ChatCompletionChunk>(data) {
            Ok(chunk) => {
                if let Some(choice) = chunk.choices.first() {
                    if let Some(content) = &choice.delta.content {
                        if !content.is_empty() {
                            results.push(Ok(content.clone()));
                        }
                    }
                }
            }
            Err(e) => {
                results.push(Err(ProviderError::StreamParse(e.to_string())));
            }
        }
    }

    results
}

#[derive(Debug, Deserialize)]
struct ModelsResponse {
    data: Vec<ModelData>,
}

#[derive(Debug, Deserialize)]
struct ModelData {
    id: String,
}

#[derive(Debug, Serialize)]
struct ChatCompletionRequest {
    model: String,
    messages: Vec<ChatMessage>,
    stream: bool,
}

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

impl From<Message> for ChatMessage {
    fn from(msg: Message) -> Self {
        Self {
            role: match msg.role {
                Role::System => "system".to_string(),
                Role::User => "user".to_string(),
                Role::Assistant => "assistant".to_string(),
            },
            content: msg.content,
        }
    }
}

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

#[derive(Debug, Deserialize)]
struct Choice {
    delta: Delta,
}

#[derive(Debug, Deserialize)]
struct Delta {
    content: Option<String>,
}