clawft-core 0.5.1

//! Quality scorers for the pipeline (Stage 5).
//!
//! Provides two implementations:
//! - [`NoopScorer`] -- Level 0 baseline (returns 1.0 for everything)
//! - [`FitnessScorer`] -- Level 1 GEPA-inspired multi-objective scorer
//!
//! The active scorer is selected by configuration. Both implement
//! [`QualityScorer`].

use clawft_types::provider::{ContentBlock, LlmResponse, StopReason};

use super::traits::{ChatRequest, QualityScore, QualityScorer};

// ─── NoopScorer (Level 0) ─────────────────────────────────────────────

/// Level 0 no-op quality scorer.
///
/// Always returns perfect scores (1.0 for all dimensions).
/// This serves as a baseline for the pipeline and will be replaced
/// by heuristic or ML-based scorers at higher levels.
pub struct NoopScorer;

impl NoopScorer {
    /// Create a new no-op scorer.
    pub fn new() -> Self {
        Self
    }
}

impl Default for NoopScorer {
    fn default() -> Self {
        Self::new()
    }
}

impl QualityScorer for NoopScorer {
    fn score(&self, _request: &ChatRequest, _response: &LlmResponse) -> QualityScore {
        QualityScore {
            overall: 1.0,
            relevance: 1.0,
            coherence: 1.0,
        }
    }
}

// ─── FitnessScorer (Level 1 -- GEPA-inspired) ────────────────────────

/// Configurable weights for multi-objective fitness scoring.
#[derive(Debug, Clone)]
pub struct FitnessScorerWeights {
    /// Weight for task completion signal (0.0--1.0).
    pub task_completion: f32,
    /// Weight for token efficiency signal (0.0--1.0).
    pub efficiency: f32,
    /// Weight for tool accuracy signal (0.0--1.0).
    pub tool_accuracy: f32,
    /// Weight for coherence / readability signal (0.0--1.0).
    pub coherence: f32,
}

impl Default for FitnessScorerWeights {
    fn default() -> Self {
        Self {
            task_completion: 0.4,
            efficiency: 0.2,
            tool_accuracy: 0.2,
            coherence: 0.2,
        }
    }
}

/// Configuration for the fitness scorer.
#[derive(Debug, Clone)]
pub struct FitnessScorerConfig {
    /// Scoring weights.
    pub weights: FitnessScorerWeights,
    /// Token budget: responses using fewer tokens score higher on efficiency.
    /// Default: 4096.
    pub token_budget: u32,
    /// Minimum response length (in chars) below which task_completion drops.
    /// Default: 10.
    pub min_response_length: usize,
    /// Error indicator phrases that reduce quality scores.
    pub error_indicators: Vec<String>,
}

impl Default for FitnessScorerConfig {
    fn default() -> Self {
        Self {
            weights: FitnessScorerWeights::default(),
            token_budget: 4096,
            min_response_length: 10,
            error_indicators: vec![
                "I can't".into(),
                "I'm unable".into(),
                "I cannot".into(),
                "I don't have access".into(),
                "I'm not able".into(),
                "as an AI".into(),
            ],
        }
    }
}

/// Level 1 multi-objective fitness scorer (GEPA-inspired).
///
/// Evaluates responses across four dimensions:
/// - **Task completion**: Did the response address the request?
/// - **Efficiency**: Token usage relative to budget
/// - **Tool accuracy**: Correct tool call patterns
/// - **Coherence**: Readability and structure quality
///
/// Produces a weighted sum as the overall score. Each dimension
/// feeds into the relevant [`QualityScore`] field.
pub struct FitnessScorer {
    config: FitnessScorerConfig,
}

impl FitnessScorer {
    /// Create a new fitness scorer with default configuration.
    pub fn new() -> Self {
        Self {
            config: FitnessScorerConfig::default(),
        }
    }

    /// Create a new fitness scorer with custom configuration.
    pub fn with_config(config: FitnessScorerConfig) -> Self {
        Self { config }
    }

    /// Score task completion (0.0--1.0).
    ///
    /// Heuristics:
    /// - Penalize empty or very short responses
    /// - Penalize error indicator phrases
    /// - Penalize MaxTokens stop reason (likely truncated)
    /// - Reward responses that contain content relevant to the request
    fn score_task_completion(&self, request: &ChatRequest, response: &LlmResponse) -> f32 {
        let response_text = extract_text(response);
        let mut score: f32 = 1.0;

        // Penalize empty response
        if response_text.is_empty() {
            return 0.0;
        }

        // Penalize very short responses
        if response_text.len() < self.config.min_response_length {
            score -= 0.3;
        }

        // Penalize error indicator phrases
        let lower = response_text.to_lowercase();
        for indicator in &self.config.error_indicators {
            if lower.contains(&indicator.to_lowercase()) {
                score -= 0.2;
                break; // Only penalize once
            }
        }

        // Penalize truncated responses (MaxTokens stop)
        if response.stop_reason == StopReason::MaxTokens {
            score -= 0.15;
        }

        // Reward keyword overlap between request and response
        let request_words = extract_request_keywords(request);
        if !request_words.is_empty() {
            let overlap = request_words
                .iter()
                .filter(|w| lower.contains(&w.to_lowercase()))
                .count();
            let overlap_ratio = overlap as f32 / request_words.len() as f32;
            // Slight boost for relevance (0..0.15)
            score += overlap_ratio * 0.15;
        }

        score.clamp(0.0, 1.0)
    }

    /// Score token efficiency (0.0--1.0).
    ///
    /// Responses that use fewer tokens relative to the budget score
    /// higher, but extremely short responses (which may indicate
    /// failure) are penalized.
    fn score_efficiency(&self, response: &LlmResponse) -> f32 {
        let output_tokens = response.usage.output_tokens as f32;
        let budget = self.config.token_budget as f32;

        if budget <= 0.0 {
            return 1.0;
        }

        let ratio = output_tokens / budget;

        if output_tokens < 2.0 {
            // Suspiciously short -- likely a failure
            return 0.2;
        }

        // Sweet spot: 5-50% of budget. Over 80% may indicate truncation.
        if ratio <= 0.5 {
            1.0
        } else if ratio <= 0.8 {
            1.0 - (ratio - 0.5) * 0.5 // Linear decay 1.0 -> 0.85
        } else {
            0.7 - (ratio - 0.8) * 1.5 // Steeper decay after 80%
        }
        .clamp(0.0, 1.0)
    }

    /// Score tool accuracy (0.0--1.0).
    ///
    /// Checks whether tool calls were made when tools were available
    /// and whether the response contains tool results.
    fn score_tool_accuracy(&self, request: &ChatRequest, response: &LlmResponse) -> f32 {
        let has_tools = !request.tools.is_empty();
        let has_tool_use = response.content.iter().any(|b| {
            matches!(b, ContentBlock::ToolUse { .. })
        });

        if !has_tools {
            // No tools defined -- full marks (not applicable)
            return 1.0;
        }

        if has_tool_use {
            // Tools were available and used -- good
            1.0
        } else {
            // Tools available but not used -- mild penalty
            // (the model may have correctly decided not to use tools)
            0.7
        }
    }

    /// Score coherence (0.0--1.0).
    ///
    /// Heuristic analysis of response structure and readability.
    fn score_coherence(&self, response: &LlmResponse) -> f32 {
        let text = extract_text(response);
        if text.is_empty() {
            return 0.0;
        }

        let mut score: f32 = 1.0;

        // Penalize extremely long single-line responses (wall of text)
        let lines: Vec<&str> = text.lines().collect();
        if lines.len() == 1 && text.len() > 500 {
            score -= 0.15;
        }

        // Reward structured responses (markdown headers, bullet points, code blocks)
        let has_structure = text.contains('#')
            || text.contains("- ")
            || text.contains("* ")
            || text.contains("```")
            || text.contains("1.");
        if has_structure && text.len() > 100 {
            score += 0.1;
        }

        // Penalize excessive repetition (naive check: repeated sentences)
        let sentences: Vec<&str> = text.split(". ").collect();
        if sentences.len() > 3 {
            let unique_count = {
                let mut seen = std::collections::HashSet::new();
                sentences.iter().filter(|s| seen.insert(s.to_lowercase())).count()
            };
            let uniqueness = unique_count as f32 / sentences.len() as f32;
            if uniqueness < 0.5 {
                score -= 0.3; // Heavy repetition
            }
        }

        score.clamp(0.0, 1.0)
    }
}

impl Default for FitnessScorer {
    fn default() -> Self {
        Self::new()
    }
}

impl QualityScorer for FitnessScorer {
    fn score(&self, request: &ChatRequest, response: &LlmResponse) -> QualityScore {
        let task_completion = self.score_task_completion(request, response);
        let efficiency = self.score_efficiency(response);
        let tool_accuracy = self.score_tool_accuracy(request, response);
        let coherence = self.score_coherence(response);

        let w = &self.config.weights;
        let overall = (task_completion * w.task_completion
            + efficiency * w.efficiency
            + tool_accuracy * w.tool_accuracy
            + coherence * w.coherence)
            .clamp(0.0, 1.0);

        QualityScore {
            overall,
            relevance: task_completion,
            coherence,
        }
    }
}

// ─── Helpers ──────────────────────────────────────────────────────────

/// Extract all text content from an LLM response.
fn extract_text(response: &LlmResponse) -> String {
    response
        .content
        .iter()
        .filter_map(|block| {
            if let ContentBlock::Text { text } = block {
                Some(text.as_str())
            } else {
                None
            }
        })
        .collect::<Vec<_>>()
        .join("\n")
}

/// Extract meaningful keywords from the request messages for
/// relevance checking.
fn extract_request_keywords(request: &ChatRequest) -> Vec<String> {
    let stop_words: &[&str] = &[
        "the", "a", "an", "is", "are", "was", "were", "be", "been", "being",
        "have", "has", "had", "do", "does", "did", "will", "would", "could",
        "should", "may", "might", "can", "shall", "to", "of", "in", "for",
        "on", "with", "at", "by", "from", "as", "into", "through", "during",
        "before", "after", "above", "below", "and", "but", "or", "nor", "not",
        "so", "yet", "both", "either", "neither", "each", "every", "all",
        "any", "few", "more", "most", "other", "some", "such", "no", "only",
        "own", "same", "than", "too", "very", "just", "because", "if", "when",
        "i", "me", "my", "you", "your", "it", "its", "we", "us", "they",
        "them", "this", "that", "these", "those", "what", "which", "who",
        "how", "please", "help",
    ];

    request
        .messages
        .iter()
        .filter(|m| m.role == "user")
        .flat_map(|m| {
            m.content
                .split_whitespace()
                .map(|w| w.trim_matches(|c: char| !c.is_alphanumeric()).to_lowercase())
                .filter(|w| w.len() > 2 && !stop_words.contains(&w.as_str()))
                .collect::<Vec<_>>()
        })
        .collect()
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::pipeline::traits::LlmMessage;
    use clawft_types::provider::{ContentBlock, StopReason, Usage};
    use std::collections::HashMap;

    fn make_request() -> ChatRequest {
        ChatRequest {
            messages: vec![LlmMessage {
                role: "user".into(),
                content: "hello".into(),
                tool_call_id: None,
                tool_calls: None,
            }],
            tools: vec![],
            model: None,
            max_tokens: None,
            temperature: None,
            auth_context: None,
            complexity_boost: 0.0,
        }
    }

    fn make_request_with_tools() -> ChatRequest {
        ChatRequest {
            messages: vec![LlmMessage {
                role: "user".into(),
                content: "Search for rust documentation".into(),
                tool_call_id: None,
                tool_calls: None,
            }],
            tools: vec![serde_json::json!({"type": "function", "name": "web_search"})],
            model: None,
            max_tokens: None,
            temperature: None,
            auth_context: None,
            complexity_boost: 0.0,
        }
    }

    fn make_response() -> LlmResponse {
        LlmResponse {
            id: "resp-1".into(),
            content: vec![ContentBlock::Text {
                text: "Hi there! I'd be happy to help you with that.".into(),
            }],
            stop_reason: StopReason::EndTurn,
            usage: Usage {
                input_tokens: 5,
                output_tokens: 15,
                total_tokens: 0,
            },
            metadata: HashMap::new(),
        }
    }

    fn make_empty_response() -> LlmResponse {
        LlmResponse {
            id: "resp-empty".into(),
            content: vec![],
            stop_reason: StopReason::EndTurn,
            usage: Usage {
                input_tokens: 5,
                output_tokens: 0,
                total_tokens: 0,
            },
            metadata: HashMap::new(),
        }
    }

    fn make_truncated_response() -> LlmResponse {
        LlmResponse {
            id: "resp-trunc".into(),
            content: vec![ContentBlock::Text {
                text: "This response was cut off because it reached the maximum".into(),
            }],
            stop_reason: StopReason::MaxTokens,
            usage: Usage {
                input_tokens: 5,
                output_tokens: 4000,
                total_tokens: 0,
            },
            metadata: HashMap::new(),
        }
    }

    fn make_error_response() -> LlmResponse {
        LlmResponse {
            id: "resp-err".into(),
            content: vec![ContentBlock::Text {
                text: "I'm unable to help with that request.".into(),
            }],
            stop_reason: StopReason::EndTurn,
            usage: Usage {
                input_tokens: 5,
                output_tokens: 10,
                total_tokens: 0,
            },
            metadata: HashMap::new(),
        }
    }

    // ── NoopScorer tests ──────────────────────────────────────────────

    #[test]
    fn noop_scorer_returns_perfect_scores() {
        let scorer = NoopScorer::new();
        let score = scorer.score(&make_request(), &make_response());
        assert!((score.overall - 1.0).abs() < f32::EPSILON);
        assert!((score.relevance - 1.0).abs() < f32::EPSILON);
        assert!((score.coherence - 1.0).abs() < f32::EPSILON);
    }

    #[test]
    fn noop_scorer_ignores_request_content() {
        let scorer = NoopScorer::new();
        let req = ChatRequest {
            messages: vec![
                LlmMessage {
                    role: "system".into(),
                    content: "You are a code reviewer.".into(),
                    tool_call_id: None,
                    tool_calls: None,
                },
                LlmMessage {
                    role: "user".into(),
                    content: "Review my code: fn main() {}".into(),
                    tool_call_id: None,
                    tool_calls: None,
                },
            ],
            tools: vec![serde_json::json!({"type": "function"})],
            model: Some("gpt-4o".into()),
            max_tokens: Some(4096),
            temperature: Some(0.0),
            auth_context: None,
            complexity_boost: 0.0,
        };
        let score = scorer.score(&req, &make_response());
        assert!((score.overall - 1.0).abs() < f32::EPSILON);
    }

    #[test]
    fn noop_scorer_ignores_response_content() {
        let scorer = NoopScorer::new();
        let score = scorer.score(&make_request(), &make_empty_response());
        assert!((score.overall - 1.0).abs() < f32::EPSILON);
    }

    #[test]
    fn noop_scorer_consistent_across_calls() {
        let scorer = NoopScorer::new();
        let score1 = scorer.score(&make_request(), &make_response());
        let score2 = scorer.score(&make_request(), &make_response());
        assert!((score1.overall - score2.overall).abs() < f32::EPSILON);
        assert!((score1.relevance - score2.relevance).abs() < f32::EPSILON);
        assert!((score1.coherence - score2.coherence).abs() < f32::EPSILON);
    }

    #[test]
    fn noop_default_trait_impl() {
        let scorer = NoopScorer;
        let score = scorer.score(&make_request(), &make_response());
        assert!((score.overall - 1.0).abs() < f32::EPSILON);
    }

    // ── FitnessScorer tests ───────────────────────────────────────────

    #[test]
    fn fitness_scorer_scores_good_response() {
        let scorer = FitnessScorer::new();
        let score = scorer.score(&make_request(), &make_response());

        assert!(score.overall > 0.5, "good response should score > 0.5, got {}", score.overall);
        assert!(score.relevance > 0.5);
        assert!(score.coherence > 0.5);
    }

    #[test]
    fn fitness_scorer_penalizes_empty_response() {
        let scorer = FitnessScorer::new();
        let score = scorer.score(&make_request(), &make_empty_response());

        // Empty response: task_completion=0, coherence=0
        assert!(score.overall < 0.5, "empty response should score < 0.5, got {}", score.overall);
    }

    #[test]
    fn fitness_scorer_penalizes_error_response() {
        let scorer = FitnessScorer::new();
        let score = scorer.score(&make_request(), &make_error_response());

        let good_score = scorer.score(&make_request(), &make_response());
        assert!(
            score.overall < good_score.overall,
            "error response ({}) should score lower than good response ({})",
            score.overall, good_score.overall
        );
    }

    #[test]
    fn fitness_scorer_penalizes_truncated_response() {
        let scorer = FitnessScorer::new();
        let score = scorer.score(&make_request(), &make_truncated_response());

        let good_score = scorer.score(&make_request(), &make_response());
        assert!(
            score.overall < good_score.overall,
            "truncated response ({}) should score lower than good response ({})",
            score.overall, good_score.overall
        );
    }

    #[test]
    fn fitness_scorer_tool_accuracy_with_no_tools() {
        let scorer = FitnessScorer::new();
        // No tools in request -> tool accuracy should be 1.0
        let tool_score = scorer.score_tool_accuracy(&make_request(), &make_response());
        assert!((tool_score - 1.0).abs() < f32::EPSILON);
    }

    #[test]
    fn fitness_scorer_tool_accuracy_without_tool_use() {
        let scorer = FitnessScorer::new();
        // Tools defined but not used -> mild penalty
        let tool_score = scorer.score_tool_accuracy(&make_request_with_tools(), &make_response());
        assert!(tool_score < 1.0);
        assert!(tool_score > 0.5);
    }

    #[test]
    fn fitness_scorer_efficiency_moderate_usage() {
        let scorer = FitnessScorer::new();
        let efficiency = scorer.score_efficiency(&make_response());
        // 15 tokens out of 4096 budget -- very efficient
        assert!(
            efficiency > 0.9,
            "low token usage should be efficient, got {}",
            efficiency
        );
    }

    #[test]
    fn fitness_scorer_efficiency_suspiciously_short() {
        let scorer = FitnessScorer::new();
        let resp = LlmResponse {
            id: "resp-tiny".into(),
            content: vec![ContentBlock::Text { text: "Ok".into() }],
            stop_reason: StopReason::EndTurn,
            usage: Usage {
                input_tokens: 5,
                output_tokens: 1,
                total_tokens: 0,
            },
            metadata: HashMap::new(),
        };
        let efficiency = scorer.score_efficiency(&resp);
        assert!(efficiency < 0.5, "suspiciously short should score low, got {}", efficiency);
    }

    #[test]
    fn fitness_scorer_custom_weights() {
        let config = FitnessScorerConfig {
            weights: FitnessScorerWeights {
                task_completion: 1.0,
                efficiency: 0.0,
                tool_accuracy: 0.0,
                coherence: 0.0,
            },
            ..Default::default()
        };
        let scorer = FitnessScorer::with_config(config);
        let score = scorer.score(&make_request(), &make_response());

        // With only task_completion weighted, overall should equal relevance
        assert!(
            (score.overall - score.relevance).abs() < 0.01,
            "overall ({}) should match relevance ({}) with task_completion-only weights",
            score.overall, score.relevance
        );
    }

    #[test]
    fn fitness_scorer_scores_between_zero_and_one() {
        let scorer = FitnessScorer::new();

        // Test with various response types
        let responses = vec![
            make_response(),
            make_empty_response(),
            make_truncated_response(),
            make_error_response(),
        ];

        for resp in &responses {
            let score = scorer.score(&make_request(), resp);
            assert!(
                score.overall >= 0.0 && score.overall <= 1.0,
                "overall must be in [0,1], got {}",
                score.overall
            );
            assert!(
                score.relevance >= 0.0 && score.relevance <= 1.0,
                "relevance must be in [0,1], got {}",
                score.relevance
            );
            assert!(
                score.coherence >= 0.0 && score.coherence <= 1.0,
                "coherence must be in [0,1], got {}",
                score.coherence
            );
        }
    }

    #[test]
    fn fitness_scorer_coherence_penalizes_wall_of_text() {
        let scorer = FitnessScorer::new();
        let wall = "a ".repeat(300);
        let resp = LlmResponse {
            id: "resp-wall".into(),
            content: vec![ContentBlock::Text { text: wall }],
            stop_reason: StopReason::EndTurn,
            usage: Usage {
                input_tokens: 5,
                output_tokens: 300,
                total_tokens: 0,
            },
            metadata: HashMap::new(),
        };
        let coherence = scorer.score_coherence(&resp);
        assert!(coherence < 1.0, "wall of text should reduce coherence, got {}", coherence);
    }

    #[test]
    fn fitness_scorer_coherence_rewards_structure() {
        let scorer = FitnessScorer::new();
        let structured = "# Title\n\n- Point 1\n- Point 2\n\nSome explanation that is long enough to qualify for the structure bonus and demonstrate good formatting.";
        let resp = LlmResponse {
            id: "resp-struct".into(),
            content: vec![ContentBlock::Text {
                text: structured.into(),
            }],
            stop_reason: StopReason::EndTurn,
            usage: Usage {
                input_tokens: 5,
                output_tokens: 30,
                total_tokens: 0,
            },
            metadata: HashMap::new(),
        };
        let coherence = scorer.score_coherence(&resp);
        assert!(coherence >= 1.0, "structured response should score high, got {}", coherence);
    }
}