use async_trait::async_trait;
use anyhow::Result;
use serde::{Deserialize, Serialize};
use futures::stream::BoxStream;

use crate::{
    models::UnifiedRequest,
    errors::AppError,
    config::AppConfig,
};
use super::{ProviderResponse, ProviderStreamChunk};

#[derive(Debug, Serialize)]
struct GeminiRequest {
    contents: Vec<GeminiContent>,
    generation_config: Option<GeminiGenerationConfig>,
}

#[derive(Debug, Serialize, Deserialize)]
struct GeminiContent {
    parts: Vec<GeminiPart>,
    role: String,
}

#[derive(Debug, Serialize, Deserialize)]
struct GeminiPart {
    #[serde(skip_serializing_if = "Option::is_none")]
    text: Option<String>,
    #[serde(skip_serializing_if = "Option::is_none")]
    inline_data: Option<GeminiInlineData>,
}

#[derive(Debug, Serialize, Deserialize)]
struct GeminiInlineData {
    mime_type: String,
    data: String,
}

#[derive(Debug, Serialize)]
struct GeminiGenerationConfig {
    temperature: Option<f64>,
    max_output_tokens: Option<u32>,
}

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

#[derive(Debug, Deserialize)]
struct GeminiUsageMetadata {
    prompt_token_count: u32,
    candidates_token_count: u32,
    total_token_count: u32,
}

#[derive(Debug, Deserialize)]
struct GeminiResponse {
    candidates: Vec<GeminiCandidate>,
    usage_metadata: Option<GeminiUsageMetadata>,
}



pub struct GeminiProvider {
    client: reqwest::Client,
    config: crate::config::GeminiConfig,
    api_key: String,
    pricing: Vec<crate::config::ModelPricing>,
}

impl GeminiProvider {
    pub fn new(config: &crate::config::GeminiConfig, app_config: &AppConfig) -> Result<Self> {
        let api_key = app_config.get_api_key("gemini")?;
        Self::new_with_key(config, app_config, api_key)
    }

    pub fn new_with_key(config: &crate::config::GeminiConfig, app_config: &AppConfig, api_key: String) -> Result<Self> {
        let client = reqwest::Client::builder()
            .timeout(std::time::Duration::from_secs(30))
            .build()?;
        
        Ok(Self {
            client,
            config: config.clone(),
            api_key,
            pricing: app_config.pricing.gemini.clone(),
        })
    }
}

#[async_trait]
impl super::Provider for GeminiProvider {
    fn name(&self) -> &str {
        "gemini"
    }

    fn supports_model(&self, model: &str) -> bool {
        model.starts_with("gemini-")
    }

    fn supports_multimodal(&self) -> bool {
        true  // Gemini supports vision
    }

    async fn chat_completion(
        &self,
        request: UnifiedRequest,
    ) -> Result<ProviderResponse, AppError> {
        // Convert UnifiedRequest to Gemini request
        let mut contents = Vec::with_capacity(request.messages.len());
        
        for msg in request.messages {
            let mut parts = Vec::with_capacity(msg.content.len());
            
            for part in msg.content {
                match part {
                    crate::models::ContentPart::Text { text } => {
                        parts.push(GeminiPart {
                            text: Some(text),
                            inline_data: None,
                        });
                    }
                    crate::models::ContentPart::Image(image_input) => {
                        let (base64_data, mime_type) = image_input.to_base64().await
                            .map_err(|e| AppError::ProviderError(format!("Failed to convert image: {}", e)))?;
                        
                        parts.push(GeminiPart {
                            text: None,
                            inline_data: Some(GeminiInlineData {
                                mime_type,
                                data: base64_data,
                            }),
                        });
                    }
                }
            }
            
            // Map role: "user" -> "user", "assistant" -> "model", "system" -> "user"
            let role = match msg.role.as_str() {
                "assistant" => "model".to_string(),
                _ => "user".to_string(),
            };
            
            contents.push(GeminiContent {
                parts,
                role,
            });
        }
        
        if contents.is_empty() {
            return Err(AppError::ProviderError("No valid text messages to send".to_string()));
        }
        
        // Build generation config
        let generation_config = if request.temperature.is_some() || request.max_tokens.is_some() {
            Some(GeminiGenerationConfig {
                temperature: request.temperature,
                max_output_tokens: request.max_tokens,
            })
        } else {
            None
        };
        
        let gemini_request = GeminiRequest {
            contents,
            generation_config,
        };
        
        // Build URL
        let url = format!("{}/models/{}:generateContent?key={}", 
            self.config.base_url, 
            request.model,
            self.api_key
        );
        
        // Send request
        let response = self.client
            .post(&url)
            .json(&gemini_request)
            .send()
            .await
            .map_err(|e| AppError::ProviderError(format!("HTTP request failed: {}", e)))?;
        
        // Check status
        let status = response.status();
        if !status.is_success() {
            let error_text = response.text().await.unwrap_or_default();
            return Err(AppError::ProviderError(format!("Gemini API error ({}): {}", status, error_text)));
        }
        
        let gemini_response: GeminiResponse = response
            .json()
            .await
            .map_err(|e| AppError::ProviderError(format!("Failed to parse response: {}", e)))?;
        
        // Extract content from first candidate
        let content = gemini_response.candidates
            .first()
            .and_then(|c| c.content.parts.first())
            .and_then(|p| p.text.clone())
            .unwrap_or_default();
        
        // Extract token usage
        let prompt_tokens = gemini_response.usage_metadata.as_ref().map(|u| u.prompt_token_count).unwrap_or(0);
        let completion_tokens = gemini_response.usage_metadata.as_ref().map(|u| u.candidates_token_count).unwrap_or(0);
        let total_tokens = gemini_response.usage_metadata.as_ref().map(|u| u.total_token_count).unwrap_or(0);
        
        Ok(ProviderResponse {
            content,
            reasoning_content: None, // Gemini doesn't use this field name
            prompt_tokens,
            completion_tokens,
            total_tokens,
            model: request.model,
        })
    }

    fn estimate_tokens(&self, request: &UnifiedRequest) -> Result<u32> {
        Ok(crate::utils::tokens::estimate_request_tokens(&request.model, request))
    }

    fn calculate_cost(&self, model: &str, prompt_tokens: u32, completion_tokens: u32, registry: &crate::models::registry::ModelRegistry) -> f64 {
        if let Some(metadata) = registry.find_model(model) {
            if let Some(cost) = &metadata.cost {
                return (prompt_tokens as f64 * cost.input / 1_000_000.0) + 
                       (completion_tokens as f64 * cost.output / 1_000_000.0);
            }
        }
        
        let (prompt_rate, completion_rate) = self.pricing.iter()
            .find(|p| model.contains(&p.model))
            .map(|p| (p.prompt_tokens_per_million, p.completion_tokens_per_million))
            .unwrap_or((0.075, 0.30)); // Default to Gemini 2.0 Flash price if not found
            
        (prompt_tokens as f64 * prompt_rate / 1_000_000.0) + (completion_tokens as f64 * completion_rate / 1_000_000.0)
    }

    async fn chat_completion_stream(
        &self,
        request: UnifiedRequest,
    ) -> Result<BoxStream<'static, Result<ProviderStreamChunk, AppError>>, AppError> {
        // Convert UnifiedRequest to Gemini request
        let mut contents = Vec::with_capacity(request.messages.len());
        
        for msg in request.messages {
            let mut parts = Vec::with_capacity(msg.content.len());
            
            for part in msg.content {
                match part {
                    crate::models::ContentPart::Text { text } => {
                        parts.push(GeminiPart {
                            text: Some(text),
                            inline_data: None,
                        });
                    }
                    crate::models::ContentPart::Image(image_input) => {
                        let (base64_data, mime_type) = image_input.to_base64().await
                            .map_err(|e| AppError::ProviderError(format!("Failed to convert image: {}", e)))?;
                        
                        parts.push(GeminiPart {
                            text: None,
                            inline_data: Some(GeminiInlineData {
                                mime_type,
                                data: base64_data,
                            }),
                        });
                    }
                }
            }
            
            // Map role
            let role = match msg.role.as_str() {
                "assistant" => "model".to_string(),
                _ => "user".to_string(),
            };
            
            contents.push(GeminiContent {
                parts,
                role,
            });
        }
        
        // Build generation config
        let generation_config = if request.temperature.is_some() || request.max_tokens.is_some() {
            Some(GeminiGenerationConfig {
                temperature: request.temperature,
                max_output_tokens: request.max_tokens,
            })
        } else {
            None
        };
        
        let gemini_request = GeminiRequest {
            contents,
            generation_config,
        };
        
        // Build URL for streaming
        let url = format!("{}/models/{}:streamGenerateContent?alt=sse&key={}", 
            self.config.base_url,
            request.model,
            self.api_key
        );
        
        // Create eventsource stream
        use reqwest_eventsource::{EventSource, Event};
        use futures::StreamExt;

        let es = EventSource::new(self.client.post(&url).json(&gemini_request))
            .map_err(|e| AppError::ProviderError(format!("Failed to create EventSource: {}", e)))?;
        
        let model = request.model.clone();
        
        let stream = async_stream::try_stream! {
            let mut es = es;
            while let Some(event) = es.next().await {
                match event {
                    Ok(Event::Message(msg)) => {
                        let gemini_response: GeminiResponse = serde_json::from_str(&msg.data)
                            .map_err(|e| AppError::ProviderError(format!("Failed to parse stream chunk: {}", e)))?;
                        
                        if let Some(candidate) = gemini_response.candidates.first() {
                            let content = candidate.content.parts.first()
                                .and_then(|p| p.text.clone())
                                .unwrap_or_default();
                            
                            yield ProviderStreamChunk {
                                content,
                                reasoning_content: None,
                                finish_reason: None, // Will be set in the last chunk
                                model: model.clone(),
                            };
                        }
                    }
                    Ok(_) => continue,
                    Err(e) => {
                        Err(AppError::ProviderError(format!("Stream error: {}", e)))?;
                    }
                }
            }
        };
        
        Ok(Box::pin(stream))
    }
}