//! AI client trait and metadata definitions.

pub mod bedrock;
pub mod claude;
pub mod claude_cli;
pub mod openai;

use std::future::Future;
use std::pin::Pin;
use std::time::Duration;

use anyhow::{Context, Result};
use reqwest::Client;
use serde_json::Value;

use crate::claude::error::ClaudeError;
use crate::claude::model_config::get_model_registry;

/// HTTP request timeout for AI API calls.
///
/// Set to 5 minutes to accommodate large prompts and long model responses
/// (up to 64k output tokens) while preventing indefinite hangs.
pub(crate) const REQUEST_TIMEOUT: Duration = Duration::from_secs(300);

/// Metadata about an AI client implementation.
#[derive(Clone, Debug)]
pub struct AiClientMetadata {
    /// Service provider name.
    pub provider: String,
    /// Model identifier.
    pub model: String,
    /// Maximum context length supported.
    pub max_context_length: usize,
    /// Maximum token response length supported.
    pub max_response_length: usize,
    /// Active beta header, if any: (key, value).
    pub active_beta: Option<(String, String)>,
}

/// Prompt formatting families for AI providers.
///
/// Determines provider-specific prompt behaviour (e.g., how template
/// instructions are phrased). Parse once at the boundary via
/// [`AiClientMetadata::prompt_style`] and match on the enum downstream.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum PromptStyle {
    /// Claude models handle "literal template" instructions correctly.
    Claude,
    /// OpenAI-compatible models (OpenAI, Ollama) need different formatting.
    OpenAi,
}

impl AiClientMetadata {
    /// Derives the prompt style from the provider name.
    ///
    /// Matches against the exact strings set by each [`AiClient`] implementation:
    /// - `"OpenAI"` and `"Ollama"` → [`PromptStyle::OpenAi`]
    /// - `"Anthropic"` and `"Anthropic Bedrock"` → [`PromptStyle::Claude`]
    ///
    /// Unrecognised provider strings default to [`PromptStyle::Claude`].
    #[must_use]
    pub fn prompt_style(&self) -> PromptStyle {
        match self.provider.as_str() {
            "OpenAI" | "Ollama" => PromptStyle::OpenAi,
            _ => PromptStyle::Claude,
        }
    }
}

// ── Shared helpers for AI client implementations ────────────────────

/// Builds an HTTP client with the standard request timeout.
pub(crate) fn build_http_client() -> Result<Client> {
    Client::builder()
        .timeout(REQUEST_TIMEOUT)
        .build()
        .context("Failed to build HTTP client")
}

/// Returns the maximum output tokens for a model from the registry,
/// respecting beta overrides.
#[must_use]
pub(crate) fn registry_max_output_tokens(
    model: &str,
    active_beta: &Option<(String, String)>,
) -> i32 {
    let registry = get_model_registry();
    if let Some((_, value)) = active_beta {
        registry.get_max_output_tokens_with_beta(model, value) as i32
    } else {
        registry.get_max_output_tokens(model) as i32
    }
}

/// Returns the (input context length, max response length) for a model
/// from the registry, respecting beta overrides.
#[must_use]
pub(crate) fn registry_model_limits(
    model: &str,
    active_beta: &Option<(String, String)>,
) -> (usize, usize) {
    let registry = get_model_registry();
    match active_beta {
        Some((_, value)) => (
            registry.get_input_context_with_beta(model, value),
            registry.get_max_output_tokens_with_beta(model, value),
        ),
        None => (
            registry.get_input_context(model),
            registry.get_max_output_tokens(model),
        ),
    }
}

/// Checks an HTTP response for error status and returns a structured error
/// if non-success.
///
/// On success, returns the response unchanged for further processing.
/// On failure, reads the error body and returns a
/// [`ClaudeError::ApiRequestFailed`].
pub(crate) async fn check_error_response(response: reqwest::Response) -> Result<reqwest::Response> {
    if response.status().is_success() {
        return Ok(response);
    }
    let status = response.status();
    let error_text = response.text().await.unwrap_or_else(|e| {
        tracing::debug!("Failed to read error response body: {e}");
        String::new()
    });
    Err(ClaudeError::ApiRequestFailed(format!("HTTP {status}: {error_text}")).into())
}

/// Logs successful text extraction from an AI API response.
pub(crate) fn log_response_success(provider: &str, result: &Result<String>) {
    if let Ok(text) = result {
        tracing::debug!(
            response_len = text.len(),
            "Successfully extracted text content from {} API response",
            provider
        );
        tracing::debug!(
            response_content = %text,
            "{} API response content",
            provider
        );
    }
}

/// Capabilities advertised by an [`AiClient`] implementation.
///
/// Used by call sites to decide whether to attach a structured-response
/// schema (or other backend-specific request options) before dispatching.
/// The default value is the conservative ''nothing supported'' baseline so
/// new fields can be added without forcing existing implementations to
/// update.
#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
pub struct AiClientCapabilities {
    /// Whether the backend can enforce a JSON Schema on its response.
    ///
    /// When `true`, the call site may set
    /// [`RequestOptions::response_schema`]; the backend will hand the schema
    /// to its underlying API (e.g. `claude -p --json-schema <file>`) and the
    /// API re-prompts until the model produces a validating response.
    pub supports_response_schema: bool,
}

/// Whether the response should be formatted as YAML (default) or JSON
/// matching a schema.
///
/// Used by the prompts module to swap the format-specific portion of a
/// structured prompt without rewriting the semantic instructions.
#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
pub enum ResponseFormat {
    /// Plain YAML, with the prompt asking the model to emit a fenced or
    /// bare YAML document.
    #[default]
    Yaml,
    /// JSON object that matches a schema attached via
    /// [`RequestOptions::response_schema`]. The prompt drops the YAML
    /// structure literal and tells the model to return only the JSON
    /// object.
    JsonSchema,
}

impl ResponseFormat {
    /// Returns the response format that should be used given a backend's
    /// capabilities.
    #[must_use]
    pub fn from_capabilities(caps: &AiClientCapabilities) -> Self {
        if caps.supports_response_schema {
            Self::JsonSchema
        } else {
            Self::Yaml
        }
    }
}

/// Per-request options passed to [`AiClient::send_request_with_options`].
///
/// Schema and other knobs live on the request, not the client, so a shared
/// client cannot leak settings between concurrent calls. Backends that do
/// not support an option are expected to ignore it (and the call site is
/// expected to consult [`AiClient::capabilities`] before setting it).
#[derive(Clone, Debug, Default)]
pub struct RequestOptions {
    /// Optional JSON Schema (as a `serde_json::Value`) constraining the
    /// model's response. Only honoured by backends whose
    /// [`AiClientCapabilities::supports_response_schema`] is `true`.
    pub response_schema: Option<Value>,
}

impl RequestOptions {
    /// Returns a new [`RequestOptions`] with [`Self::response_schema`] set.
    #[must_use]
    pub fn with_response_schema(mut self, schema: Value) -> Self {
        self.response_schema = Some(schema);
        self
    }
}

/// Trait for AI service clients.
pub trait AiClient: Send + Sync {
    /// Sends a request to the AI service and returns the raw response.
    fn send_request<'a>(
        &'a self,
        system_prompt: &'a str,
        user_prompt: &'a str,
    ) -> Pin<Box<dyn Future<Output = Result<String>> + Send + 'a>>;

    /// Returns metadata about the AI client implementation.
    fn get_metadata(&self) -> AiClientMetadata;

    /// Returns the optional capabilities advertised by this backend.
    ///
    /// The default implementation returns the all-disabled baseline so
    /// existing backends remain source-compatible. Backends that gain new
    /// capabilities (e.g. structured-output enforcement) should override
    /// this method.
    fn capabilities(&self) -> AiClientCapabilities {
        AiClientCapabilities::default()
    }

    /// Sends a request with optional per-request settings.
    ///
    /// The default implementation drops `options` and dispatches via
    /// [`Self::send_request`]. Backends that honour any field in
    /// [`RequestOptions`] (e.g. `response_schema`) override this method.
    /// Backends that don't honour an option must ignore it; call sites
    /// should consult [`capabilities`](Self::capabilities) before setting
    /// options that not all backends support.
    fn send_request_with_options<'a>(
        &'a self,
        system_prompt: &'a str,
        user_prompt: &'a str,
        _options: RequestOptions,
    ) -> Pin<Box<dyn Future<Output = Result<String>> + Send + 'a>> {
        self.send_request(system_prompt, user_prompt)
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    fn meta(provider: &str) -> AiClientMetadata {
        AiClientMetadata {
            provider: provider.to_string(),
            model: "test-model".to_string(),
            max_context_length: 1024,
            max_response_length: 1024,
            active_beta: None,
        }
    }

    #[test]
    fn prompt_style_openai() {
        assert_eq!(meta("OpenAI").prompt_style(), PromptStyle::OpenAi);
    }

    #[test]
    fn prompt_style_ollama() {
        assert_eq!(meta("Ollama").prompt_style(), PromptStyle::OpenAi);
    }

    #[test]
    fn prompt_style_anthropic() {
        assert_eq!(meta("Anthropic").prompt_style(), PromptStyle::Claude);
    }

    #[test]
    fn prompt_style_bedrock() {
        assert_eq!(
            meta("Anthropic Bedrock").prompt_style(),
            PromptStyle::Claude
        );
    }

    #[test]
    fn prompt_style_unknown_defaults_to_claude() {
        assert_eq!(meta("SomeNewProvider").prompt_style(), PromptStyle::Claude);
    }

    /// Ensure case-sensitive matching: "openai" (lowercase) is not a known provider
    /// string and must not silently match as OpenAI.
    #[test]
    fn prompt_style_case_sensitive() {
        assert_eq!(meta("openai").prompt_style(), PromptStyle::Claude);
        assert_eq!(meta("ollama").prompt_style(), PromptStyle::Claude);
    }

    #[test]
    fn capabilities_default_is_all_disabled() {
        let caps = AiClientCapabilities::default();
        assert!(!caps.supports_response_schema);
    }

    #[test]
    fn response_format_default_is_yaml() {
        assert_eq!(ResponseFormat::default(), ResponseFormat::Yaml);
    }

    #[test]
    fn response_format_from_capabilities_disabled_picks_yaml() {
        let caps = AiClientCapabilities::default();
        assert_eq!(
            ResponseFormat::from_capabilities(&caps),
            ResponseFormat::Yaml
        );
    }

    #[test]
    fn response_format_from_capabilities_enabled_picks_json_schema() {
        let caps = AiClientCapabilities {
            supports_response_schema: true,
        };
        assert_eq!(
            ResponseFormat::from_capabilities(&caps),
            ResponseFormat::JsonSchema
        );
    }

    #[test]
    fn request_options_with_response_schema_sets_field() {
        let value = serde_json::json!({"type": "object"});
        let opts = RequestOptions::default().with_response_schema(value.clone());
        assert_eq!(opts.response_schema, Some(value));
    }

    #[test]
    fn request_options_default_has_no_schema() {
        let opts = RequestOptions::default();
        assert!(opts.response_schema.is_none());
    }
}
