use super::traits::{Memory, MemoryEntry};

/// Minimum message length (chars) to trigger keyword expansion query.
const MIN_EXPANSION_LENGTH: usize = 30;

/// Minimum word length to keep in keyword extraction.
const MIN_KEYWORD_LENGTH: usize = 4;

/// Enhanced memory retrieval with multi-query expansion.
///
/// 1. Runs the primary recall with the full query.
/// 2. For long messages, extracts significant keywords and runs a second recall,
///    merging results (deduplicated by key, keeping the higher score).
/// 3. Returns the top `limit` entries sorted by score descending.
pub async fn enhanced_recall(
    mem: &dyn Memory,
    query: &str,
    limit: usize,
    session_id: Option<&str>,
) -> Vec<MemoryEntry> {
    // Primary recall with full query
    let mut results = mem.recall(query, limit, session_id).await.unwrap_or_default();

    // Multi-query expansion for long messages
    if query.len() >= MIN_EXPANSION_LENGTH {
        let keywords = extract_keywords(query);
        if !keywords.is_empty() && keywords != query.trim() {
            if let Ok(extra) = mem.recall(&keywords, limit, session_id).await {
                merge_entries(&mut results, extra);
            }
        }
    }

    // Sort by score descending, take top `limit`
    results.sort_by(|a, b| {
        b.score
            .unwrap_or(0.0)
            .partial_cmp(&a.score.unwrap_or(0.0))
            .unwrap_or(std::cmp::Ordering::Equal)
    });
    results.truncate(limit);

    results
}

/// Extract significant keywords (length >= 4) from a message.
fn extract_keywords(msg: &str) -> String {
    msg.split_whitespace()
        .filter_map(|w| {
            let clean = w.trim_matches(|c: char| !c.is_alphanumeric());
            if clean.len() >= MIN_KEYWORD_LENGTH {
                Some(clean)
            } else {
                None
            }
        })
        .collect::<Vec<_>>()
        .join(" ")
}

/// Merge extra entries into results, deduplicating by key (keep highest score).
fn merge_entries(results: &mut Vec<MemoryEntry>, extra: Vec<MemoryEntry>) {
    for entry in extra {
        if let Some(existing) = results.iter_mut().find(|r| r.key == entry.key) {
            if entry.score.unwrap_or(0.0) > existing.score.unwrap_or(0.0) {
                existing.score = entry.score;
            }
        } else {
            results.push(entry);
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::memory::traits::MemoryCategory;
    use async_trait::async_trait;

    #[test]
    fn extract_keywords_filters_short_words() {
        assert_eq!(
            extract_keywords("I want to use PostgreSQL for the database"),
            "want PostgreSQL database"
        );
    }

    #[test]
    fn extract_keywords_strips_punctuation() {
        // trim_matches strips non-alphanumeric from both ends:
        // "config?" -> "config", "settings." -> "settings", "what's" stays (apostrophe is internal)
        assert_eq!(
            extract_keywords("what's the config? check settings."),
            "what's config check settings"
        );
    }

    #[test]
    fn extract_keywords_empty_for_short_words() {
        assert_eq!(extract_keywords("I am ok"), "");
    }

    #[test]
    fn merge_entries_deduplicates_by_key_keeping_higher_score() {
        let mut results = vec![MemoryEntry {
            id: "1".into(),
            key: "db".into(),
            content: "PostgreSQL".into(),
            category: MemoryCategory::Core,
            timestamp: "now".into(),
            session_id: None,
            score: Some(0.6),
        }];
        let extra = vec![
            MemoryEntry {
                id: "1b".into(),
                key: "db".into(),
                content: "PostgreSQL".into(),
                category: MemoryCategory::Core,
                timestamp: "now".into(),
                session_id: None,
                score: Some(0.9), // higher
            },
            MemoryEntry {
                id: "2".into(),
                key: "lang".into(),
                content: "Rust".into(),
                category: MemoryCategory::Core,
                timestamp: "now".into(),
                session_id: None,
                score: Some(0.7),
            },
        ];
        merge_entries(&mut results, extra);
        assert_eq!(results.len(), 2);
        assert_eq!(results[0].score, Some(0.9)); // upgraded
        assert_eq!(results[1].key, "lang"); // new entry added
    }

    struct MockMemory {
        primary: Vec<MemoryEntry>,
        keyword: Vec<MemoryEntry>,
        call_count: std::sync::atomic::AtomicUsize,
    }

    #[async_trait]
    impl Memory for MockMemory {
        async fn store(
            &self, _k: &str, _c: &str, _cat: MemoryCategory, _s: Option<&str>,
        ) -> anyhow::Result<()> {
            Ok(())
        }
        async fn recall(
            &self, _query: &str, _limit: usize, _s: Option<&str>,
        ) -> anyhow::Result<Vec<MemoryEntry>> {
            // First call returns primary results, second call returns keyword results
            let n = self.call_count.fetch_add(1, std::sync::atomic::Ordering::SeqCst);
            if n == 0 {
                Ok(self.primary.clone())
            } else {
                Ok(self.keyword.clone())
            }
        }
        async fn get(&self, _k: &str) -> anyhow::Result<Option<MemoryEntry>> {
            Ok(None)
        }
        async fn list(
            &self, _c: Option<&MemoryCategory>, _s: Option<&str>,
        ) -> anyhow::Result<Vec<MemoryEntry>> {
            Ok(vec![])
        }
        async fn forget(&self, _k: &str) -> anyhow::Result<bool> {
            Ok(true)
        }
        async fn count(&self) -> anyhow::Result<usize> {
            Ok(0)
        }
        async fn health_check(&self) -> bool {
            true
        }
        fn name(&self) -> &str {
            "mock"
        }
    }

    #[tokio::test]
    async fn enhanced_recall_merges_primary_and_keyword_results() {
        let mem = MockMemory {
            primary: vec![MemoryEntry {
                id: "1".into(),
                key: "db".into(),
                content: "PostgreSQL".into(),
                category: MemoryCategory::Core,
                timestamp: "now".into(),
                session_id: None,
                score: Some(0.7),
            }],
            keyword: vec![MemoryEntry {
                id: "2".into(),
                key: "lang".into(),
                content: "Rust".into(),
                category: MemoryCategory::Conversation,
                timestamp: "now".into(),
                session_id: None,
                score: Some(0.6),
            }],
            call_count: std::sync::atomic::AtomicUsize::new(0),
        };

        // Long query triggers expansion
        let query = "what database and programming language should we use for this project";
        let results = enhanced_recall(&mem, query, 5, None).await;

        assert_eq!(results.len(), 2);
        // "db" has higher score (0.7), ranked first
        assert_eq!(results[0].key, "db");
        assert_eq!(results[0].score, Some(0.7));
        // "lang" from keyword expansion
        assert_eq!(results[1].key, "lang");
        assert_eq!(results[1].score, Some(0.6));
    }

    #[tokio::test]
    async fn enhanced_recall_skips_expansion_for_short_query() {
        let mem = MockMemory {
            primary: vec![MemoryEntry {
                id: "1".into(),
                key: "db".into(),
                content: "PostgreSQL".into(),
                category: MemoryCategory::Core,
                timestamp: "now".into(),
                session_id: None,
                score: Some(0.7),
            }],
            keyword: vec![MemoryEntry {
                id: "2".into(),
                key: "lang".into(),
                content: "Rust".into(),
                category: MemoryCategory::Conversation,
                timestamp: "now".into(),
                session_id: None,
                score: Some(0.6),
            }],
            call_count: std::sync::atomic::AtomicUsize::new(0),
        };

        // Short query — no expansion, so "keyword" recall is what gets returned
        // (because our mock returns keyword results for short queries)
        let results = enhanced_recall(&mem, "database?", 5, None).await;

        // Only keyword results returned (mock behavior), no merge
        assert_eq!(results.len(), 1);
    }

    #[tokio::test]
    async fn enhanced_recall_respects_limit() {
        let mem = MockMemory {
            primary: (0..10)
                .map(|i| MemoryEntry {
                    id: format!("{i}"),
                    key: format!("key_{i}"),
                    content: format!("val_{i}"),
                    category: MemoryCategory::Conversation,
                    timestamp: "now".into(),
                    session_id: None,
                    score: Some(0.5 + i as f64 * 0.01),
                })
                .collect(),
            keyword: vec![],
            call_count: std::sync::atomic::AtomicUsize::new(0),
        };

        let results = enhanced_recall(
            &mem,
            "a very long query that definitely triggers keyword expansion for testing purposes",
            3,
            None,
        )
        .await;

        assert_eq!(results.len(), 3);
    }
}