use anyhow::{Error, Result};
use async_trait::async_trait;
use serde_json::{json, Value};

use super::api_client::{ApiClient, AuthMethod};
use super::base::{ConfigKey, Provider, ProviderMetadata, ProviderUsage, Usage};
use super::errors::ProviderError;
use super::retry::ProviderRetry;
use super::utils::{
    get_model, handle_response_google_compat, handle_response_openai_compat, is_google_model,
    RequestLog,
};
use crate::conversation::message::Message;

use crate::model::ModelConfig;
use crate::providers::formats::openai::{create_request, get_usage, response_to_message};
use rmcp::model::Tool;

pub const OPENROUTER_DEFAULT_MODEL: &str = "anthropic/claude-sonnet-4";
pub const OPENROUTER_DEFAULT_FAST_MODEL: &str = "google/gemini-flash-2.5";
pub const OPENROUTER_MODEL_PREFIX_ANTHROPIC: &str = "anthropic";

// OpenRouter can run many models, we suggest the default
pub const OPENROUTER_KNOWN_MODELS: &[&str] = &[
    "anthropic/claude-sonnet-4.5",
    "anthropic/claude-sonnet-4",
    "anthropic/claude-opus-4.1",
    "anthropic/claude-opus-4",
    "anthropic/claude-3.7-sonnet",
    "google/gemini-2.5-pro",
    "google/gemini-2.5-flash",
    "deepseek/deepseek-r1-0528",
    "qwen/qwen3-coder",
    "moonshotai/kimi-k2",
];
pub const OPENROUTER_DOC_URL: &str = "https://openrouter.ai/models";

#[derive(serde::Serialize)]
pub struct OpenRouterProvider {
    #[serde(skip)]
    api_client: ApiClient,
    model: ModelConfig,
    #[serde(skip)]
    name: String,
}

impl OpenRouterProvider {
    pub async fn from_env(model: ModelConfig) -> Result<Self> {
        let model = model.with_fast(OPENROUTER_DEFAULT_FAST_MODEL.to_string());

        let config = crate::config::Config::global();
        let api_key: String = config.get_secret("OPENROUTER_API_KEY")?;
        let host: String = config
            .get_param("OPENROUTER_HOST")
            .unwrap_or_else(|_| "https://openrouter.ai".to_string());

        let auth = AuthMethod::BearerToken(api_key);
        let api_client = ApiClient::new(host, auth)?
            .with_header("HTTP-Referer", "https://block.github.io/goose")?
            .with_header("X-Title", "goose")?;

        Ok(Self {
            api_client,
            model,
            name: Self::metadata().name,
        })
    }

    async fn post(&self, payload: &Value) -> Result<Value, ProviderError> {
        let response = self
            .api_client
            .response_post("api/v1/chat/completions", payload)
            .await?;

        // Handle Google-compatible model responses differently
        if is_google_model(payload) {
            return handle_response_google_compat(response).await;
        }

        // For OpenAI-compatible models, parse the response body to JSON
        let response_body = handle_response_openai_compat(response)
            .await
            .map_err(|e| ProviderError::RequestFailed(format!("Failed to parse response: {e}")))?;

        let _debug = format!(
            "OpenRouter request with payload: {} and response: {}",
            serde_json::to_string_pretty(payload).unwrap_or_else(|_| "Invalid JSON".to_string()),
            serde_json::to_string_pretty(&response_body)
                .unwrap_or_else(|_| "Invalid JSON".to_string())
        );

        // OpenRouter can return errors in 200 OK responses, so we have to check for errors explicitly
        // https://openrouter.ai/docs/api-reference/errors
        if let Some(error_obj) = response_body.get("error") {
            // If there's an error object, extract the error message and code
            let error_message = error_obj
                .get("message")
                .and_then(|m| m.as_str())
                .unwrap_or("Unknown OpenRouter error");

            let error_code = error_obj.get("code").and_then(|c| c.as_u64()).unwrap_or(0);

            // Check for context length errors in the error message
            if error_code == 400 && error_message.contains("maximum context length") {
                return Err(ProviderError::ContextLengthExceeded(
                    error_message.to_string(),
                ));
            }

            // Return appropriate error based on the OpenRouter error code
            match error_code {
                401 | 403 => return Err(ProviderError::Authentication(error_message.to_string())),
                429 => {
                    return Err(ProviderError::RateLimitExceeded {
                        details: error_message.to_string(),
                        retry_delay: None,
                    })
                }
                500 | 503 => return Err(ProviderError::ServerError(error_message.to_string())),
                _ => return Err(ProviderError::RequestFailed(error_message.to_string())),
            }
        }

        // No error detected, return the response body
        Ok(response_body)
    }
}

/// Update the request when using anthropic model.
/// For anthropic model, we can enable prompt caching to save cost. Since openrouter is the OpenAI compatible
/// endpoint, we need to modify the open ai request to have anthropic cache control field.
fn update_request_for_anthropic(original_payload: &Value) -> Value {
    let mut payload = original_payload.clone();

    if let Some(messages_spec) = payload
        .as_object_mut()
        .and_then(|obj| obj.get_mut("messages"))
        .and_then(|messages| messages.as_array_mut())
    {
        // Add "cache_control" to the last and second-to-last "user" messages.
        // During each turn, we mark the final message with cache_control so the conversation can be
        // incrementally cached. The second-to-last user message is also marked for caching with the
        // cache_control parameter, so that this checkpoint can read from the previous cache.
        let mut user_count = 0;
        for message in messages_spec.iter_mut().rev() {
            if message.get("role") == Some(&json!("user")) {
                if let Some(content) = message.get_mut("content") {
                    if let Some(content_str) = content.as_str() {
                        *content = json!([{
                            "type": "text",
                            "text": content_str,
                            "cache_control": { "type": "ephemeral" }
                        }]);
                    }
                }
                user_count += 1;
                if user_count >= 2 {
                    break;
                }
            }
        }

        // Update the system message to have cache_control field.
        if let Some(system_message) = messages_spec
            .iter_mut()
            .find(|msg| msg.get("role") == Some(&json!("system")))
        {
            if let Some(content) = system_message.get_mut("content") {
                if let Some(content_str) = content.as_str() {
                    *system_message = json!({
                        "role": "system",
                        "content": [{
                            "type": "text",
                            "text": content_str,
                            "cache_control": { "type": "ephemeral" }
                        }]
                    });
                }
            }
        }
    }

    if let Some(tools_spec) = payload
        .as_object_mut()
        .and_then(|obj| obj.get_mut("tools"))
        .and_then(|tools| tools.as_array_mut())
    {
        // Add "cache_control" to the last tool spec, if any. This means that all tool definitions,
        // will be cached as a single prefix.
        if let Some(last_tool) = tools_spec.last_mut() {
            if let Some(function) = last_tool.get_mut("function") {
                function
                    .as_object_mut()
                    .unwrap()
                    .insert("cache_control".to_string(), json!({ "type": "ephemeral" }));
            }
        }
    }
    payload
}

async fn create_request_based_on_model(
    provider: &OpenRouterProvider,
    system: &str,
    messages: &[Message],
    tools: &[Tool],
) -> anyhow::Result<Value, Error> {
    let mut payload = create_request(
        &provider.model,
        system,
        messages,
        tools,
        &super::utils::ImageFormat::OpenAi,
    )?;

    if provider.supports_cache_control().await {
        payload = update_request_for_anthropic(&payload);
    }

    // Always add transforms: ["middle-out"] for OpenRouter to handle prompts > context size
    payload
        .as_object_mut()
        .unwrap()
        .insert("transforms".to_string(), json!(["middle-out"]));

    Ok(payload)
}

#[async_trait]
impl Provider for OpenRouterProvider {
    fn metadata() -> ProviderMetadata {
        ProviderMetadata::new(
            "openrouter",
            "OpenRouter",
            "Router for many model providers",
            OPENROUTER_DEFAULT_MODEL,
            OPENROUTER_KNOWN_MODELS.to_vec(),
            OPENROUTER_DOC_URL,
            vec![
                ConfigKey::new("OPENROUTER_API_KEY", true, true, None),
                ConfigKey::new(
                    "OPENROUTER_HOST",
                    false,
                    false,
                    Some("https://openrouter.ai"),
                ),
            ],
        )
    }

    fn get_name(&self) -> &str {
        &self.name
    }

    fn get_model_config(&self) -> ModelConfig {
        self.model.clone()
    }

    #[tracing::instrument(
        skip(self, model_config, system, messages, tools),
        fields(model_config, input, output, input_tokens, output_tokens, total_tokens)
    )]
    async fn complete_with_model(
        &self,
        model_config: &ModelConfig,
        system: &str,
        messages: &[Message],
        tools: &[Tool],
    ) -> Result<(Message, ProviderUsage), ProviderError> {
        let payload = create_request_based_on_model(self, system, messages, tools).await?;
        let mut log = RequestLog::start(model_config, &payload)?;

        // Make request
        let response = self
            .with_retry(|| async {
                let payload_clone = payload.clone();
                self.post(&payload_clone).await
            })
            .await?;

        // Parse response
        let message = response_to_message(&response)?;
        let usage = response.get("usage").map(get_usage).unwrap_or_else(|| {
            tracing::debug!("Failed to get usage data");
            Usage::default()
        });
        let response_model = get_model(&response);
        log.write(&response, Some(&usage))?;
        Ok((message, ProviderUsage::new(response_model, usage)))
    }

    /// Fetch supported models from OpenRouter API (only models with tool support)
    async fn fetch_supported_models(&self) -> Result<Option<Vec<String>>, ProviderError> {
        // Handle request failures gracefully
        // If the request fails, fall back to manual entry
        let response = match self.api_client.response_get("api/v1/models").await {
            Ok(response) => response,
            Err(e) => {
                tracing::warn!("Failed to fetch models from OpenRouter API: {}, falling back to manual model entry", e);
                return Ok(None);
            }
        };

        // Handle JSON parsing failures gracefully
        let json: serde_json::Value = match response.json().await {
            Ok(json) => json,
            Err(e) => {
                tracing::warn!("Failed to parse OpenRouter API response as JSON: {}, falling back to manual model entry", e);
                return Ok(None);
            }
        };

        // Check for error in response
        if let Some(err_obj) = json.get("error") {
            let msg = err_obj
                .get("message")
                .and_then(|v| v.as_str())
                .unwrap_or("unknown error");
            tracing::warn!("OpenRouter API returned an error: {}", msg);
            return Ok(None);
        }

        let data = json.get("data").and_then(|v| v.as_array()).ok_or_else(|| {
            ProviderError::UsageError("Missing data field in JSON response".into())
        })?;

        let mut models: Vec<String> = data
            .iter()
            .filter_map(|model| {
                // Get the model ID
                let id = model.get("id").and_then(|v| v.as_str())?;

                // Check if the model supports tools
                let supported_params =
                    match model.get("supported_parameters").and_then(|v| v.as_array()) {
                        Some(params) => params,
                        None => {
                            // If supported_parameters is missing, skip this model (assume no tool support)
                            tracing::debug!(
                                "Model '{}' missing supported_parameters field, skipping",
                                id
                            );
                            return None;
                        }
                    };

                let has_tool_support = supported_params
                    .iter()
                    .any(|param| param.as_str() == Some("tools"));

                if has_tool_support {
                    Some(id.to_string())
                } else {
                    None
                }
            })
            .collect();

        // If no models with tool support were found, fall back to manual entry
        if models.is_empty() {
            tracing::warn!("No models with tool support found in OpenRouter API response, falling back to manual model entry");
            return Ok(None);
        }

        models.sort();
        Ok(Some(models))
    }

    async fn supports_cache_control(&self) -> bool {
        self.model
            .model_name
            .starts_with(OPENROUTER_MODEL_PREFIX_ANTHROPIC)
    }
}