use std::fmt;
use std::sync::Arc;

use config::AppConfig;
use rig::providers::openai;

use crate::error::{AiError, AiResult};

fn validate_required(scope: &str, field: &str, value: &str) -> AiResult<()> {
    if value.trim().is_empty() {
        return Err(AiError::Config(format!("{scope} {field} is required")));
    }
    Ok(())
}

fn config_error(error: impl fmt::Display) -> AiError {
    AiError::Config(error.to_string())
}

#[derive(Clone)]
pub struct EndpointConfig {
    pub base_url: String,
    pub api_key: String,
}

impl EndpointConfig {
    pub fn new(base_url: impl Into<String>, api_key: impl Into<String>) -> AiResult<Self> {
        let config = Self {
            base_url: base_url.into(),
            api_key: api_key.into(),
        };
        config.validate("endpoint")?;
        Ok(config)
    }

    fn validate(&self, scope: &str) -> AiResult<()> {
        validate_required(scope, "base_url", &self.base_url)?;
        validate_required(scope, "api_key", &self.api_key)?;
        if !self.base_url.trim().starts_with("http://")
            && !self.base_url.trim().starts_with("https://")
        {
            return Err(AiError::Config(format!(
                "{scope} base_url must start with http:// or https://"
            )));
        }
        Ok(())
    }

    pub fn build_client(&self) -> AiResult<openai::Client> {
        openai::Client::builder()
            .api_key(&self.api_key)
            .base_url(self.base_url.trim())
            .build()
            .map_err(|e| AiError::Config(format!("failed to build rig OpenAI client: {e}")))
    }
}

impl fmt::Debug for EndpointConfig {
    fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
        formatter
            .debug_struct("EndpointConfig")
            .field("base_url", &self.base_url)
            .field("api_key", &"<redacted>")
            .finish()
    }
}

#[derive(Clone, Debug)]
pub struct EmbedConfig {
    pub endpoint: EndpointConfig,
    pub model: String,
    pub dimensions: u64,
}

impl EmbedConfig {
    pub fn new(
        endpoint: EndpointConfig,
        model: impl Into<String>,
        dimensions: u64,
    ) -> AiResult<Self> {
        let config = Self {
            endpoint,
            model: model.into(),
            dimensions,
        };
        config.validate()?;
        Ok(config)
    }

    fn validate(&self) -> AiResult<()> {
        self.endpoint.validate("embed endpoint")?;
        validate_required("embed", "model", &self.model)?;
        if self.dimensions == 0 {
            return Err(AiError::Config(
                "embed dimensions must be greater than 0".to_string(),
            ));
        }
        Ok(())
    }
}

#[derive(Clone, Debug)]
pub struct AiClientConfig {
    pub llm: EndpointConfig,
    pub embed: EmbedConfig,
}

impl AiClientConfig {
    pub fn new(llm: EndpointConfig, embed: EmbedConfig) -> AiResult<Self> {
        let config = Self { llm, embed };
        config.validate()?;
        Ok(config)
    }

    pub fn validate(&self) -> AiResult<()> {
        self.llm.validate("llm endpoint")?;
        self.embed.validate()?;
        Ok(())
    }
}

impl TryFrom<&AppConfig> for AiClientConfig {
    type Error = AiError;

    fn try_from(config: &AppConfig) -> Result<Self, Self::Error> {
        let llm = EndpointConfig::new(
            config.ai_basic_url().map_err(config_error)?,
            config.ai_api_key().map_err(config_error)?,
        )?;

        let embed_endpoint = EndpointConfig::new(
            config.get_embed_model_base_url().map_err(config_error)?,
            config.get_embed_model_api_key().map_err(config_error)?,
        )?;

        let embed = EmbedConfig::new(
            embed_endpoint,
            config.get_embed_model_name().map_err(config_error)?,
            config.get_embed_model_dimensions().map_err(config_error)?,
        )?;

        Self::new(llm, embed)
    }
}

#[derive(Clone, Debug)]
pub struct AiClient {
    pub(super) llm_client: openai::Client,
    pub(super) embed_client: openai::Client,
    pub(super) config: Arc<AiClientConfig>,
}

impl AiClient {
    pub fn new(config: AiClientConfig) -> AiResult<Self> {
        config.validate()?;

        Ok(Self {
            llm_client: config.llm.build_client()?,
            embed_client: config.embed.endpoint.build_client()?,
            config: Arc::new(config),
        })
    }

    pub fn from_app_config(config: &AppConfig) -> AiResult<Self> {
        Self::new(AiClientConfig::try_from(config)?)
    }

    pub fn llm_client(&self) -> &openai::Client {
        &self.llm_client
    }

    pub fn embed_client(&self) -> &openai::Client {
        &self.embed_client
    }

    pub fn config(&self) -> &AiClientConfig {
        &self.config
    }

    pub fn llm_config(&self) -> &EndpointConfig {
        &self.config.llm
    }

    pub fn embed_config(&self) -> &EmbedConfig {
        &self.config.embed
    }

    pub fn embed_model(&self) -> &str {
        self.config.embed.model.as_str()
    }

    pub fn embed_dimensions(&self) -> u64 {
        self.config.embed.dimensions
    }

    pub fn embed_dimensions_u32(&self) -> u32 {
        u32::try_from(self.config.embed.dimensions).unwrap_or(u32::MAX)
    }
}

pub fn build_http_client() -> Result<reqwest::Client, AiError> {
    let mut builder = reqwest::Client::builder();

    if let Ok(proxy_url) = std::env::var("HTTPS_PROXY")
        .or_else(|_| std::env::var("https_proxy"))
        .or_else(|_| std::env::var("HTTP_PROXY"))
        .or_else(|_| std::env::var("http_proxy"))
    {
        let proxy_url = proxy_url.trim().trim_matches('"').trim_matches('\'');
        let proxy = reqwest::Proxy::all(proxy_url).map_err(|e| {
            AiError::Config(format!("Invalid proxy URL '{}': {}", proxy_url, e))
        })?;
        builder = builder.proxy(proxy);
    }

    builder.build().map_err(|e| {
        AiError::Config(format!("Failed to build HTTP client: {}", e))
    })
}