dissolve-python 0.3.0

// Copyright (C) 2024 Jelmer Vernooij <jelmer@samba.org>
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! Performance optimizations including caching and string interning

use rustpython_ast as ast;
use std::collections::HashMap;
use std::hash::Hash;
use std::sync::{Arc, Mutex, RwLock};

/// String interning system for reducing memory usage
pub struct StringInterner {
    strings: RwLock<HashMap<String, Arc<str>>>,
}

impl StringInterner {
    pub fn new() -> Self {
        Self {
            strings: RwLock::new(HashMap::new()),
        }
    }

    /// Intern a string, returning an Arc to the shared copy
    pub fn intern(&self, s: &str) -> Arc<str> {
        // First try to read and see if we already have it
        if let Ok(map) = self.strings.read() {
            if let Some(interned) = map.get(s) {
                return Arc::clone(interned);
            }
        }

        // Need to insert it - get write lock
        let mut map = self.strings.write().unwrap();
        if let Some(interned) = map.get(s) {
            // Someone else might have inserted it while we were waiting for write lock
            Arc::clone(interned)
        } else {
            let arc: Arc<str> = Arc::from(s);
            map.insert(s.to_string(), Arc::clone(&arc));
            arc
        }
    }

    /// Get statistics about the interner
    pub fn stats(&self) -> InternerStats {
        let map = self.strings.read().unwrap();
        InternerStats {
            unique_strings: map.len(),
            total_bytes_saved: map.iter().map(|(k, _)| k.len()).sum::<usize>()
                * (std::mem::size_of::<String>() - std::mem::size_of::<Arc<str>>()),
        }
    }
}

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

#[derive(Debug, Clone)]
pub struct InternerStats {
    pub unique_strings: usize,
    pub total_bytes_saved: usize,
}

/// Cache for parsed ASTs to avoid re-parsing the same files
pub struct AstCache {
    cache: RwLock<HashMap<String, CacheEntry>>,
    max_entries: usize,
}

#[derive(Clone)]
struct CacheEntry {
    ast: ast::Mod,
    last_modified: std::time::SystemTime,
    hit_count: usize,
}

impl AstCache {
    pub fn new(max_entries: usize) -> Self {
        Self {
            cache: RwLock::new(HashMap::new()),
            max_entries,
        }
    }

    /// Get an AST from cache if it exists and is up to date
    pub fn get(&self, file_path: &str, file_modified: std::time::SystemTime) -> Option<ast::Mod> {
        let mut cache = self.cache.write().ok()?;

        if let Some(entry) = cache.get_mut(file_path) {
            if entry.last_modified >= file_modified {
                entry.hit_count += 1;
                return Some(entry.ast.clone());
            } else {
                // File was modified, remove stale entry
                cache.remove(file_path);
            }
        }
        None
    }

    /// Store an AST in the cache
    pub fn insert(&self, file_path: String, ast: ast::Mod, file_modified: std::time::SystemTime) {
        let mut cache = self.cache.write().unwrap();

        // If we're at capacity, remove the least recently used entry
        if cache.len() >= self.max_entries {
            if let Some(lru_key) = cache
                .iter()
                .min_by_key(|(_, entry)| entry.hit_count)
                .map(|(k, _)| k.clone())
            {
                cache.remove(&lru_key);
            }
        }

        cache.insert(
            file_path,
            CacheEntry {
                ast,
                last_modified: file_modified,
                hit_count: 0,
            },
        );
    }

    /// Get cache statistics
    pub fn stats(&self) -> CacheStats {
        let cache = self.cache.read().unwrap();
        let total_hits: usize = cache.values().map(|e| e.hit_count).sum();

        CacheStats {
            entries: cache.len(),
            total_hits,
            hit_ratio: if cache.len() > 0 {
                total_hits as f64 / cache.len() as f64
            } else {
                0.0
            },
        }
    }

    /// Clear the cache
    pub fn clear(&self) {
        self.cache.write().unwrap().clear();
    }
}

#[derive(Debug, Clone)]
pub struct CacheStats {
    pub entries: usize,
    pub total_hits: usize,
    pub hit_ratio: f64,
}

/// Cache for type information to reduce LSP queries
pub struct TypeCache {
    cache: RwLock<HashMap<TypeQuery, TypeInfo>>,
    max_entries: usize,
}

#[derive(Debug, Clone, Hash, PartialEq, Eq)]
pub struct TypeQuery {
    pub file_path: String,
    pub line: usize,
    pub column: usize,
    pub expression: String,
}

#[derive(Debug, Clone)]
pub struct TypeInfo {
    pub type_name: String,
    pub is_callable: bool,
    pub cached_at: std::time::Instant,
    pub ttl: std::time::Duration, // Time to live
}

impl TypeCache {
    pub fn new(max_entries: usize) -> Self {
        Self {
            cache: RwLock::new(HashMap::new()),
            max_entries,
        }
    }

    pub fn get(&self, query: &TypeQuery) -> Option<TypeInfo> {
        let mut cache = self.cache.write().ok()?;

        if let Some(info) = cache.get(query) {
            // Check if the entry has expired
            if info.cached_at.elapsed() < info.ttl {
                return Some(info.clone());
            } else {
                // Entry expired, remove it
                cache.remove(query);
            }
        }
        None
    }

    pub fn insert(&self, query: TypeQuery, info: TypeInfo) {
        let mut cache = self.cache.write().unwrap();

        // If we're at capacity, remove some expired entries first
        if cache.len() >= self.max_entries {
            let now = std::time::Instant::now();
            cache.retain(|_, info| now.duration_since(info.cached_at) < info.ttl);

            // If still at capacity, remove oldest entries
            if cache.len() >= self.max_entries {
                let oldest_keys: Vec<_> = cache
                    .iter()
                    .map(|(k, v)| (k.clone(), v.cached_at))
                    .collect::<Vec<_>>()
                    .into_iter()
                    .sorted_by_key(|(_, cached_at)| *cached_at)
                    .take(cache.len() - self.max_entries + 1)
                    .map(|(k, _)| k)
                    .collect();

                for key in oldest_keys {
                    cache.remove(&key);
                }
            }
        }

        cache.insert(query, info);
    }

    pub fn stats(&self) -> CacheStats {
        let cache = self.cache.read().unwrap();
        CacheStats {
            entries: cache.len(),
            total_hits: 0, // We don't track hits for type cache yet
            hit_ratio: 0.0,
        }
    }
}

/// Performance monitoring and statistics
pub struct PerformanceMonitor {
    pub string_interner: Arc<StringInterner>,
    pub ast_cache: Arc<AstCache>,
    pub type_cache: Arc<TypeCache>,
    start_time: std::time::Instant,
    files_processed: Arc<Mutex<usize>>,
    total_parse_time: Arc<Mutex<std::time::Duration>>,
    total_migration_time: Arc<Mutex<std::time::Duration>>,
}

impl PerformanceMonitor {
    pub fn new(max_ast_entries: usize, max_type_entries: usize) -> Self {
        Self {
            string_interner: Arc::new(StringInterner::new()),
            ast_cache: Arc::new(AstCache::new(max_ast_entries)),
            type_cache: Arc::new(TypeCache::new(max_type_entries)),
            start_time: std::time::Instant::now(),
            files_processed: Arc::new(Mutex::new(0)),
            total_parse_time: Arc::new(Mutex::new(std::time::Duration::ZERO)),
            total_migration_time: Arc::new(Mutex::new(std::time::Duration::ZERO)),
        }
    }

    pub fn record_file_processed(&self) {
        *self.files_processed.lock().unwrap() += 1;
    }

    pub fn record_parse_time(&self, duration: std::time::Duration) {
        *self.total_parse_time.lock().unwrap() += duration;
    }

    pub fn record_migration_time(&self, duration: std::time::Duration) {
        *self.total_migration_time.lock().unwrap() += duration;
    }

    pub fn summary(&self) -> PerformanceSummary {
        let files_processed = *self.files_processed.lock().unwrap();
        let total_parse_time = *self.total_parse_time.lock().unwrap();
        let total_migration_time = *self.total_migration_time.lock().unwrap();
        let total_time = self.start_time.elapsed();

        PerformanceSummary {
            total_time,
            files_processed,
            files_per_second: if total_time.as_secs() > 0 {
                files_processed as f64 / total_time.as_secs_f64()
            } else {
                0.0
            },
            total_parse_time,
            total_migration_time,
            average_parse_time: if files_processed > 0 {
                total_parse_time / files_processed as u32
            } else {
                std::time::Duration::ZERO
            },
            average_migration_time: if files_processed > 0 {
                total_migration_time / files_processed as u32
            } else {
                std::time::Duration::ZERO
            },
            interner_stats: self.string_interner.stats(),
            ast_cache_stats: self.ast_cache.stats(),
            type_cache_stats: self.type_cache.stats(),
        }
    }
}

#[derive(Debug, Clone)]
pub struct PerformanceSummary {
    pub total_time: std::time::Duration,
    pub files_processed: usize,
    pub files_per_second: f64,
    pub total_parse_time: std::time::Duration,
    pub total_migration_time: std::time::Duration,
    pub average_parse_time: std::time::Duration,
    pub average_migration_time: std::time::Duration,
    pub interner_stats: InternerStats,
    pub ast_cache_stats: CacheStats,
    pub type_cache_stats: CacheStats,
}

impl std::fmt::Display for PerformanceSummary {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        writeln!(f, "Performance Summary:")?;
        writeln!(f, "  Total time: {:.2?}", self.total_time)?;
        writeln!(f, "  Files processed: {}", self.files_processed)?;
        writeln!(f, "  Files per second: {:.2}", self.files_per_second)?;
        writeln!(f, "  Total parse time: {:.2?}", self.total_parse_time)?;
        writeln!(
            f,
            "  Total migration time: {:.2?}",
            self.total_migration_time
        )?;
        writeln!(f, "  Average parse time: {:.2?}", self.average_parse_time)?;
        writeln!(
            f,
            "  Average migration time: {:.2?}",
            self.average_migration_time
        )?;
        writeln!(
            f,
            "  String interner: {} unique strings",
            self.interner_stats.unique_strings
        )?;
        writeln!(
            f,
            "  AST cache: {} entries, {:.1}% hit rate",
            self.ast_cache_stats.entries,
            self.ast_cache_stats.hit_ratio * 100.0
        )?;
        writeln!(f, "  Type cache: {} entries", self.type_cache_stats.entries)?;
        Ok(())
    }
}

/// Helper trait for sorting - we need this because we can't use itertools
trait SortedIterator: Iterator {
    fn sorted_by_key<K, F>(self, f: F) -> std::vec::IntoIter<Self::Item>
    where
        Self: Sized,
        F: FnMut(&Self::Item) -> K,
        K: Ord,
    {
        let mut v: Vec<Self::Item> = self.collect();
        v.sort_by_key(f);
        v.into_iter()
    }
}

impl<I: Iterator> SortedIterator for I {}

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

    #[test]
    fn test_string_interner() {
        let interner = StringInterner::new();

        let s1 = interner.intern("hello");
        let s2 = interner.intern("hello");
        let s3 = interner.intern("world");

        // Same string should return same Arc
        assert!(Arc::ptr_eq(&s1, &s2));
        assert!(!Arc::ptr_eq(&s1, &s3));

        let stats = interner.stats();
        assert_eq!(stats.unique_strings, 2);
    }

    #[test]
    fn test_ast_cache() {
        let cache = AstCache::new(2);
        let now = std::time::SystemTime::now();

        // Create a dummy AST
        let module = ast::Mod::Module(ast::ModModule {
            body: vec![],
            type_ignores: vec![],
            range: Default::default(),
        });

        // Insert and retrieve
        cache.insert("test.py".to_string(), module.clone(), now);
        let retrieved = cache.get("test.py", now);
        assert!(retrieved.is_some());

        // Should miss for modified file
        let later = now + std::time::Duration::from_secs(1);
        let missed = cache.get("test.py", later);
        assert!(missed.is_none());
    }

    #[test]
    fn test_type_cache() {
        let cache = TypeCache::new(10);

        let query = TypeQuery {
            file_path: "test.py".to_string(),
            line: 10,
            column: 5,
            expression: "func()".to_string(),
        };

        let info = TypeInfo {
            type_name: "str".to_string(),
            is_callable: false,
            cached_at: std::time::Instant::now(),
            ttl: std::time::Duration::from_secs(60),
        };

        cache.insert(query.clone(), info);
        let retrieved = cache.get(&query);
        assert!(retrieved.is_some());
    }
}