use secrecy::{ExposeSecret, SecretString};

use crate::config::helpers::optional_env;
use crate::error::ConfigError;
use crate::settings::Settings;

/// Embeddings provider configuration.
#[derive(Debug, Clone)]
pub struct EmbeddingsConfig {
    /// Whether embeddings are enabled.
    pub enabled: bool,
    /// Provider to use: "openai", "nearai", or "ollama"
    pub provider: String,
    /// OpenAI API key (for OpenAI provider).
    pub openai_api_key: Option<SecretString>,
    /// Model to use for embeddings.
    pub model: String,
    /// Ollama base URL (for Ollama provider). Defaults to http://localhost:11434.
    pub ollama_base_url: String,
    /// Embedding vector dimension. Inferred from the model name when not set explicitly.
    pub dimension: usize,
}

impl Default for EmbeddingsConfig {
    fn default() -> Self {
        let model = "text-embedding-3-small".to_string();
        let dimension = default_dimension_for_model(&model);
        Self {
            enabled: false,
            provider: "openai".to_string(),
            openai_api_key: None,
            model,
            ollama_base_url: "http://localhost:11434".to_string(),
            dimension,
        }
    }
}

/// Infer the embedding dimension from a well-known model name.
///
/// Falls back to 1536 (OpenAI text-embedding-3-small default) for unknown models.
fn default_dimension_for_model(model: &str) -> usize {
    match model {
        "text-embedding-3-small" => 1536,
        "text-embedding-3-large" => 3072,
        "text-embedding-ada-002" => 1536,
        "nomic-embed-text" => 768,
        "mxbai-embed-large" => 1024,
        "all-minilm" => 384,
        _ => 1536,
    }
}

impl EmbeddingsConfig {
    pub(crate) fn resolve(settings: &Settings) -> Result<Self, ConfigError> {
        let openai_api_key = optional_env("OPENAI_API_KEY")?.map(SecretString::from);

        let provider = optional_env("EMBEDDING_PROVIDER")?
            .unwrap_or_else(|| settings.embeddings.provider.clone());

        let model =
            optional_env("EMBEDDING_MODEL")?.unwrap_or_else(|| settings.embeddings.model.clone());

        let ollama_base_url = optional_env("OLLAMA_BASE_URL")?
            .or_else(|| settings.ollama_base_url.clone())
            .unwrap_or_else(|| "http://localhost:11434".to_string());

        let dimension = optional_env("EMBEDDING_DIMENSION")?
            .map(|s| s.parse::<usize>())
            .transpose()
            .map_err(|e| ConfigError::InvalidValue {
                key: "EMBEDDING_DIMENSION".to_string(),
                message: format!("must be a positive integer: {e}"),
            })?
            .unwrap_or_else(|| default_dimension_for_model(&model));

        let enabled = optional_env("EMBEDDING_ENABLED")?
            .map(|s| s.parse())
            .transpose()
            .map_err(|e| ConfigError::InvalidValue {
                key: "EMBEDDING_ENABLED".to_string(),
                message: format!("must be 'true' or 'false': {e}"),
            })?
            .unwrap_or(settings.embeddings.enabled);

        Ok(Self {
            enabled,
            provider,
            openai_api_key,
            model,
            ollama_base_url,
            dimension,
        })
    }

    /// Get the OpenAI API key if configured.
    pub fn openai_api_key(&self) -> Option<&str> {
        self.openai_api_key.as_ref().map(|s| s.expose_secret())
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::config::helpers::ENV_MUTEX;
    use crate::settings::{EmbeddingsSettings, Settings};

    /// Clear all embedding-related env vars.
    fn clear_embedding_env() {
        // SAFETY: Only called under ENV_MUTEX in tests.
        unsafe {
            std::env::remove_var("EMBEDDING_ENABLED");
            std::env::remove_var("EMBEDDING_PROVIDER");
            std::env::remove_var("EMBEDDING_MODEL");
            std::env::remove_var("OPENAI_API_KEY");
        }
    }

    #[test]
    fn embeddings_disabled_not_overridden_by_openai_key() {
        let _guard = ENV_MUTEX.lock().expect("env mutex poisoned");

        clear_embedding_env();
        // SAFETY: Under ENV_MUTEX, no concurrent env access.
        unsafe {
            std::env::set_var("OPENAI_API_KEY", "sk-test-key-for-issue-129");
        }

        let settings = Settings {
            embeddings: EmbeddingsSettings {
                enabled: false,
                ..Default::default()
            },
            ..Default::default()
        };

        let config = EmbeddingsConfig::resolve(&settings).expect("resolve should succeed");
        assert!(
            !config.enabled,
            "embeddings should remain disabled when settings.embeddings.enabled=false, \
             even when OPENAI_API_KEY is set (issue #129)"
        );

        // SAFETY: Under ENV_MUTEX.
        unsafe {
            std::env::remove_var("OPENAI_API_KEY");
        }
    }

    #[test]
    fn embeddings_enabled_from_settings() {
        let _guard = ENV_MUTEX.lock().expect("env mutex poisoned");
        clear_embedding_env();

        let settings = Settings {
            embeddings: EmbeddingsSettings {
                enabled: true,
                ..Default::default()
            },
            ..Default::default()
        };

        let config = EmbeddingsConfig::resolve(&settings).expect("resolve should succeed");
        assert!(
            config.enabled,
            "embeddings should be enabled when settings say so"
        );
    }

    #[test]
    fn embeddings_env_override_takes_precedence() {
        let _guard = ENV_MUTEX.lock().expect("env mutex poisoned");

        clear_embedding_env();
        // SAFETY: Under ENV_MUTEX.
        unsafe {
            std::env::set_var("EMBEDDING_ENABLED", "true");
        }

        let settings = Settings {
            embeddings: EmbeddingsSettings {
                enabled: false,
                ..Default::default()
            },
            ..Default::default()
        };

        let config = EmbeddingsConfig::resolve(&settings).expect("resolve should succeed");
        assert!(
            config.enabled,
            "EMBEDDING_ENABLED=true env var should override settings"
        );

        // SAFETY: Under ENV_MUTEX.
        unsafe {
            std::env::remove_var("EMBEDDING_ENABLED");
        }
    }
}