use crate::config::paths::Paths;
use anyhow::{anyhow, Context, Result};
use async_trait::async_trait;
use axum::http;
use chrono::{DateTime, Utc};
use reqwest::Client;
use serde::{Deserialize, Serialize};
use serde_json::Value;
use std::cell::RefCell;
use std::collections::HashMap;
use std::path::PathBuf;
use std::time::Duration;

use super::base::{Provider, ProviderMetadata, ProviderUsage, Usage};
use super::errors::ProviderError;
use super::formats::openai::{create_request, get_usage, response_to_message};
use super::retry::ProviderRetry;
use super::utils::{get_model, handle_response_openai_compat, ImageFormat, RequestLog};

use crate::config::{Config, ConfigError};
use crate::conversation::message::Message;

use crate::model::ModelConfig;
use crate::providers::base::ConfigKey;
use rmcp::model::Tool;

pub const GITHUB_COPILOT_DEFAULT_MODEL: &str = "gpt-4.1";
pub const GITHUB_COPILOT_KNOWN_MODELS: &[&str] = &[
    "gpt-4.1",
    "gpt-5-mini",
    "gpt-5",
    "gpt-4o",
    "grok-code-fast-1",
    "gpt-5-codex",
    "claude-sonnet-4",
    "claude-sonnet-4.5",
    "claude-haiku-4.5",
    "gemini-2.5-pro",
];

pub const GITHUB_COPILOT_STREAM_MODELS: &[&str] = &[
    "gpt-4.1",
    "gpt-5",
    "gpt-5-mini",
    "gpt-5-codex",
    "claude-sonnet-4",
    "claude-sonnet-4.5",
    "claude-haiku-4.5",
    "gemini-2.5-pro",
    "grok-code-fast-1",
];

const GITHUB_COPILOT_DOC_URL: &str =
    "https://docs.github.com/en/copilot/using-github-copilot/ai-models";
const GITHUB_COPILOT_CLIENT_ID: &str = "Iv1.b507a08c87ecfe98";
const GITHUB_COPILOT_DEVICE_CODE_URL: &str = "https://github.com/login/device/code";
const GITHUB_COPILOT_ACCESS_TOKEN_URL: &str = "https://github.com/login/oauth/access_token";
const GITHUB_COPILOT_API_KEY_URL: &str = "https://api.github.com/copilot_internal/v2/token";

#[derive(Debug, Deserialize)]
struct DeviceCodeInfo {
    device_code: String,
    user_code: String,
    verification_uri: String,
}

#[derive(Debug, Serialize, Deserialize, Clone)]
struct CopilotTokenEndpoints {
    api: String,
    #[serde(flatten)]
    _extra: HashMap<String, Value>,
}

#[derive(Debug, Serialize, Deserialize, Clone)]
#[allow(dead_code)] // useful for debugging
struct CopilotTokenInfo {
    token: String,
    expires_at: i64,
    refresh_in: i64,
    endpoints: CopilotTokenEndpoints,
    #[serde(flatten)]
    _extra: HashMap<String, Value>,
}

#[derive(Debug, Serialize, Deserialize, Clone)]
struct CopilotState {
    expires_at: DateTime<Utc>,
    info: CopilotTokenInfo,
}

#[derive(Debug)]
struct DiskCache {
    cache_path: PathBuf,
}

impl DiskCache {
    fn new() -> Self {
        let cache_path = Paths::in_config_dir("githubcopilot/info.json");
        Self { cache_path }
    }

    async fn load(&self) -> Option<CopilotState> {
        if let Ok(contents) = tokio::fs::read_to_string(&self.cache_path).await {
            if let Ok(info) = serde_json::from_str::<CopilotState>(&contents) {
                return Some(info);
            }
        }
        None
    }

    async fn save(&self, info: &CopilotState) -> Result<()> {
        if let Some(parent) = self.cache_path.parent() {
            tokio::fs::create_dir_all(parent).await?;
        }
        let contents = serde_json::to_string(info)?;
        tokio::fs::write(&self.cache_path, contents).await?;
        Ok(())
    }
}

#[derive(Debug, serde::Serialize)]
pub struct GithubCopilotProvider {
    #[serde(skip)]
    client: Client,
    #[serde(skip)]
    cache: DiskCache,
    #[serde(skip)]
    mu: tokio::sync::Mutex<RefCell<Option<CopilotState>>>,
    model: ModelConfig,
    #[serde(skip)]
    name: String,
}

impl GithubCopilotProvider {
    fn payload_contains_image(payload: &Value) -> bool {
        payload
            .get("messages")
            .and_then(|m| m.as_array())
            .is_some_and(|messages| {
                messages.iter().any(|msg| {
                    msg.get("content").is_some_and(|content| {
                        content
                            .as_array()
                            .map(|arr| arr.iter().collect::<Vec<_>>())
                            .unwrap_or_else(|| vec![content])
                            .iter()
                            .any(|item| {
                                matches!(
                                    item.get("type").and_then(|v| v.as_str()),
                                    Some("image_url") | Some("image")
                                )
                            })
                    })
                })
            })
    }

    pub async fn from_env(model: ModelConfig) -> Result<Self> {
        let client = Client::builder()
            .timeout(Duration::from_secs(600))
            .build()?;
        let cache = DiskCache::new();
        let mu = tokio::sync::Mutex::new(RefCell::new(None));
        Ok(Self {
            client,
            cache,
            mu,
            model,
            name: Self::metadata().name,
        })
    }

    async fn post(&self, payload: &mut Value) -> Result<Value, ProviderError> {
        use crate::providers::utils_universal_openai_stream::{OAIStreamChunk, OAIStreamCollector};
        use futures::StreamExt;
        // Detect gpt-4.1 and stream
        let model_name = payload.get("model").and_then(|v| v.as_str()).unwrap_or("");
        let stream_only_model = GITHUB_COPILOT_STREAM_MODELS
            .iter()
            .any(|prefix| model_name.starts_with(prefix));
        if stream_only_model {
            payload
                .as_object_mut()
                .unwrap()
                .insert("stream".to_string(), serde_json::Value::Bool(true));
        }
        let (endpoint, token) = self.get_api_info().await?;
        let url = url::Url::parse(&format!("{}/chat/completions", endpoint))
            .map_err(|e| ProviderError::RequestFailed(format!("Invalid base URL: {e}")))?;

        let headers = self.get_github_headers();

        let mut request = self
            .client
            .post(url)
            .headers(headers)
            .header("Authorization", format!("Bearer {}", token));

        if Self::payload_contains_image(payload) {
            request = request.header("Copilot-Vision-Request", "true");
        }

        let response = request.json(payload).send().await?;

        if stream_only_model {
            let mut collector = OAIStreamCollector::new();
            let mut stream = response.bytes_stream();
            while let Some(chunk) = stream.next().await {
                let chunk = chunk.map_err(|e| ProviderError::RequestFailed(e.to_string()))?;
                let text = String::from_utf8_lossy(&chunk);
                for line in text.lines() {
                    let tline = line.trim();
                    if !tline.starts_with("data: ") {
                        continue;
                    }
                    let Some(payload) = tline.get(6..) else {
                        continue;
                    };
                    if payload == "[DONE]" {
                        break;
                    }
                    match serde_json::from_str::<OAIStreamChunk>(payload) {
                        Ok(ch) => collector.add_chunk(&ch),
                        Err(_) => continue,
                    }
                }
            }
            let final_response = collector.build_response();
            let value = serde_json::to_value(final_response)
                .map_err(|e| ProviderError::RequestFailed(e.to_string()))?;
            Ok(value)
        } else {
            handle_response_openai_compat(response).await
        }
    }

    async fn get_api_info(&self) -> Result<(String, String)> {
        let guard = self.mu.lock().await;

        if let Some(state) = guard.borrow().as_ref() {
            if state.expires_at > Utc::now() {
                return Ok((state.info.endpoints.api.clone(), state.info.token.clone()));
            }
        }

        if let Some(state) = self.cache.load().await {
            if guard.borrow().is_none() {
                guard.replace(Some(state.clone()));
            }
            if state.expires_at > Utc::now() {
                return Ok((state.info.endpoints.api, state.info.token));
            }
        }

        const MAX_ATTEMPTS: i32 = 3;
        for attempt in 0..MAX_ATTEMPTS {
            tracing::trace!("attempt {} to refresh api info", attempt + 1);
            let info = match self.refresh_api_info().await {
                Ok(data) => data,
                Err(err) => {
                    tracing::warn!("failed to refresh api info: {}", err);
                    continue;
                }
            };
            let expires_at = Utc::now() + chrono::Duration::seconds(info.refresh_in);
            let new_state = CopilotState { info, expires_at };
            self.cache.save(&new_state).await?;
            guard.replace(Some(new_state.clone()));
            return Ok((new_state.info.endpoints.api, new_state.info.token));
        }
        Err(anyhow!("failed to get api info after 3 attempts"))
    }

    async fn refresh_api_info(&self) -> Result<CopilotTokenInfo> {
        let config = Config::global();
        let token = match config.get_secret::<String>("GITHUB_COPILOT_TOKEN") {
            Ok(token) => token,
            Err(err) => match err {
                ConfigError::NotFound(_) => {
                    let token = self
                        .get_access_token()
                        .await
                        .context("unable to login into github")?;
                    config.set_secret("GITHUB_COPILOT_TOKEN", &token)?;
                    token
                }
                _ => return Err(err.into()),
            },
        };
        let resp = self
            .client
            .get(GITHUB_COPILOT_API_KEY_URL)
            .headers(self.get_github_headers())
            .header(http::header::AUTHORIZATION, format!("bearer {}", &token))
            .send()
            .await?
            .error_for_status()?
            .text()
            .await?;
        tracing::trace!("copilot token response: {}", resp);
        let info: CopilotTokenInfo = serde_json::from_str(&resp)?;
        Ok(info)
    }

    async fn get_access_token(&self) -> Result<String> {
        for attempt in 0..3 {
            tracing::trace!("attempt {} to get access token", attempt + 1);
            match self.login().await {
                Ok(token) => return Ok(token),
                Err(err) => tracing::warn!("failed to get access token: {}", err),
            }
        }
        Err(anyhow!("failed to get access token after 3 attempts"))
    }

    async fn login(&self) -> Result<String> {
        let device_code_info = self.get_device_code().await?;

        println!(
            "Please visit {} and enter code {}",
            device_code_info.verification_uri, device_code_info.user_code
        );

        self.poll_for_access_token(&device_code_info.device_code)
            .await
    }

    async fn get_device_code(&self) -> Result<DeviceCodeInfo> {
        #[derive(Serialize)]
        struct DeviceCodeRequest {
            client_id: String,
            scope: String,
        }
        self.client
            .post(GITHUB_COPILOT_DEVICE_CODE_URL)
            .headers(self.get_github_headers())
            .json(&DeviceCodeRequest {
                client_id: GITHUB_COPILOT_CLIENT_ID.to_string(),
                scope: "read:user".to_string(),
            })
            .send()
            .await
            .context("failed to send request to get device code")?
            .error_for_status()
            .context("failed to get device code")?
            .json::<DeviceCodeInfo>()
            .await
            .context("failed to parse device code response")
    }

    async fn poll_for_access_token(&self, device_code: &str) -> Result<String> {
        #[derive(Serialize)]
        struct AccessTokenRequest {
            client_id: String,
            device_code: String,
            grant_type: String,
        }
        #[derive(Debug, Deserialize)]
        struct AccessTokenResponse {
            access_token: Option<String>,
            error: Option<String>,
            #[serde(flatten)]
            _extra: HashMap<String, Value>,
        }

        const MAX_ATTEMPTS: i32 = 36;
        for attempt in 0..MAX_ATTEMPTS {
            let resp = self
                .client
                .post(GITHUB_COPILOT_ACCESS_TOKEN_URL)
                .headers(self.get_github_headers())
                .json(&AccessTokenRequest {
                    client_id: GITHUB_COPILOT_CLIENT_ID.to_string(),
                    device_code: device_code.to_string(),
                    grant_type: "urn:ietf:params:oauth:grant-type:device_code".to_string(),
                })
                .send()
                .await
                .context("failed to make request while polling for access token")?
                .error_for_status()
                .context("error polling for access token")?
                .json::<AccessTokenResponse>()
                .await
                .context("failed to parse response while polling for access token")?;
            if resp.access_token.is_some() {
                tracing::trace!("successful authorization: {:#?}", resp,);
            }
            if let Some(access_token) = resp.access_token {
                return Ok(access_token);
            } else if resp
                .error
                .as_ref()
                .is_some_and(|err| err == "authorization_pending")
            {
                tracing::debug!(
                    "authorization pending (attempt {}/{})",
                    attempt + 1,
                    MAX_ATTEMPTS
                );
            } else {
                tracing::debug!("unexpected response: {:#?}", resp);
            }
            tokio::time::sleep(tokio::time::Duration::from_secs(5)).await;
        }
        Err(anyhow!("failed to get access token"))
    }

    fn get_github_headers(&self) -> http::HeaderMap {
        let mut headers = http::HeaderMap::new();
        headers.insert(http::header::ACCEPT, "application/json".parse().unwrap());
        headers.insert(
            http::header::CONTENT_TYPE,
            "application/json".parse().unwrap(),
        );
        headers.insert(
            http::header::USER_AGENT,
            "GithubCopilot/1.155.0".parse().unwrap(),
        );
        headers.insert("editor-version", "vscode/1.85.1".parse().unwrap());
        headers.insert("editor-plugin-version", "copilot/1.155.0".parse().unwrap());
        headers
    }
}

#[async_trait]
impl Provider for GithubCopilotProvider {
    fn metadata() -> ProviderMetadata {
        ProviderMetadata::new(
            "github_copilot",
            "GitHub Copilot",
            "GitHub Copilot. Run `goose configure` and select copilot to set up.",
            GITHUB_COPILOT_DEFAULT_MODEL,
            GITHUB_COPILOT_KNOWN_MODELS.to_vec(),
            GITHUB_COPILOT_DOC_URL,
            vec![ConfigKey::new_oauth(
                "GITHUB_COPILOT_TOKEN",
                true,
                true,
                None,
            )],
        )
    }

    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(
            model_config,
            system,
            messages,
            tools,
            &ImageFormat::OpenAi,
            false,
        )?;
        let mut log = RequestLog::start(model_config, &payload)?;

        // Make request with retry
        let response = self
            .with_retry(|| async {
                let mut payload_clone = payload.clone();
                self.post(&mut 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 GitHub Copliot; returns Err on failure, Ok(None) if not present
    async fn fetch_supported_models(&self) -> Result<Option<Vec<String>>, ProviderError> {
        let (endpoint, token) = self.get_api_info().await?;
        let url = format!("{}/models", endpoint);

        let mut headers = http::HeaderMap::new();
        headers.insert(http::header::ACCEPT, "application/json".parse().unwrap());
        headers.insert(
            http::header::CONTENT_TYPE,
            "application/json".parse().unwrap(),
        );
        headers.insert("Copilot-Integration-Id", "vscode-chat".parse().unwrap());
        headers.insert(
            http::header::AUTHORIZATION,
            format!("Bearer {}", token).parse().unwrap(),
        );

        let response = self.client.get(url).headers(headers).send().await?;

        let json: serde_json::Value = response.json().await?;

        let arr = match json.get("data").and_then(|v| v.as_array()) {
            Some(arr) => arr,
            None => return Ok(None),
        };
        let mut models: Vec<String> = arr
            .iter()
            .filter_map(|m| {
                if let Some(s) = m.as_str() {
                    Some(s.to_string())
                } else if let Some(obj) = m.as_object() {
                    obj.get("id").and_then(|v| v.as_str()).map(str::to_string)
                } else {
                    None
                }
            })
            .collect();
        models.sort();
        Ok(Some(models))
    }

    async fn configure_oauth(&self) -> Result<(), ProviderError> {
        let config = Config::global();

        // Check if token already exists and is valid
        if config.get_secret::<String>("GITHUB_COPILOT_TOKEN").is_ok() {
            // Try to refresh API info to validate the token
            match self.refresh_api_info().await {
                Ok(_) => return Ok(()), // Token is valid
                Err(_) => {
                    // Token is invalid, continue with OAuth flow
                    tracing::debug!("Existing token is invalid, starting OAuth flow");
                }
            }
        }

        // Start OAuth device code flow
        let token = self
            .get_access_token()
            .await
            .map_err(|e| ProviderError::Authentication(format!("OAuth flow failed: {}", e)))?;

        // Save the token
        config
            .set_secret("GITHUB_COPILOT_TOKEN", &token)
            .map_err(|e| ProviderError::ExecutionError(format!("Failed to save token: {}", e)))?;

        Ok(())
    }
}