Add result caching to solar api months endpoint

src/solar_api/src/main.rs

@@ -1,6 +1,8 @@
 use chrono;
 use clap::Parser;
+use shared_api_lib::year_month::{YearMonth, YearMonthRange};
 use std::collections::HashMap;
+use std::sync::RwLock;
 use warp::Filter;
 use warp::http::Response;
 
@@ -98,6 +100,8 @@ async fn serve(configuration: &std::sync::Arc<CommandLineArgs>) {
             },
         );
 
+    let month_cache: std::sync::Arc<RwLock<Vec<CachedMonthsResponseItem>>> =
+        std::sync::Arc::new(RwLock::new(Vec::new()));
     let months = warp::get()
         .and(warp::path("months"))
         .and(warp::query::<HashMap<String, String>>())
@@ -105,8 +109,14 @@ async fn serve(configuration: &std::sync::Arc<CommandLineArgs>) {
             let configuration = configuration.clone();
             move || configuration.clone()
         }))
+        .and(warp::any().map({
+            let month_cache = month_cache.clone();
+            move || month_cache.clone()
+        }))
         .map(
-            |query: HashMap<String, String>, configuration: std::sync::Arc<CommandLineArgs>| {
+            |query: HashMap<String, String>,
+             configuration: std::sync::Arc<CommandLineArgs>,
+             month_cache| {
                 let maybe_start =
                     shared_api_lib::query_helpers::try_parse_query_month_year(query.get("start"));
                 if maybe_start.is_none() {
@@ -131,7 +141,8 @@ async fn serve(configuration: &std::sync::Arc<CommandLineArgs>) {
                     ));
                 }
 
-                let json = get_months_solar_json(&start, &stop, &configuration.database_path);
+                let json =
+                    get_months_solar_json(&start, &stop, &configuration.database_path, month_cache);
                 return Response::builder()
                     .header("Content-Type", "application/json")
                     .body(json);
@@ -241,23 +252,95 @@ struct DaysResponseItem {
 }
 
 fn get_months_solar_json(
-    start: &shared_api_lib::year_month::YearMonth,
-    stop: &shared_api_lib::year_month::YearMonth,
+    start: &YearMonth,
+    stop: &YearMonth,
     database_path: &str,
+    month_cache: std::sync::Arc<RwLock<Vec<CachedMonthsResponseItem>>>,
 ) -> String {
-    let summaries = database::get_month_solar_summaries(&start, &stop, &database_path);
     let mut response_model = MonthsResponse {
-        month_logs: Vec::new(),
+        month_logs: YearMonthRange::new(start, stop)
+            .unwrap()
+            .map(|ym| MonthsResponseItem {
+                year: ym.year,
+                month: ym.month,
+                envoy_total_watts: 0,
+                zever_total_watts: 0,
+            })
+            .collect(),
     };
 
-    for summary in summaries {
-        response_model.month_logs.push(MonthsResponseItem {
-            year: summary.year,
-            month: summary.month,
-            envoy_total_watts: summary.envoy_total_watts,
-            zever_total_watts: summary.zever_total_watts,
+    let cached_months = get_cached_months_solar_json(&start, &stop, &month_cache);
+    let mut missing_months;
+    if cached_months.len() > 0 {
+        missing_months = Vec::new();
+        let mut cached_month_next_index = 0;
+        for month in response_model.month_logs.iter_mut() {
+            if cached_month_next_index < cached_months.len() {
+                let cached_month = &cached_months[cached_month_next_index];
+                if month.year == cached_month.year && month.month == cached_month.month {
+                    month.envoy_total_watts = cached_month.envoy_total_watts;
+                    month.zever_total_watts = cached_month.zever_total_watts;
+
+                    cached_month_next_index += 1;
+                    continue;
+                }
+            }
+
+            missing_months.push(YearMonth {
+                year: month.year,
+                month: month.month,
             });
         }
+    } else {
+        missing_months = response_model
+            .month_logs
+            .iter()
+            .map(|i| YearMonth {
+                year: i.year,
+                month: i.month,
+            })
+            .collect();
+    }
+
+    if missing_months.len() > 0 {
+        let missing_ranges = compact_missing_dates_to_ranges(&missing_months);
+        for range in missing_ranges {
+            let range_start = range.start();
+            let summaries =
+                get_month_summary_range_from_database(&range_start, &range.stop(), &database_path);
+
+            let mut response_item_index = response_model
+                .month_logs
+                .iter()
+                .enumerate()
+                .find_map(|(index, item)| {
+                    if item.year == range_start.year && item.month == range_start.month {
+                        return Some(index);
+                    }
+
+                    return None;
+                })
+                .unwrap();
+            for summary in summaries.iter() {
+                let mut response_model_item = &mut response_model.month_logs[response_item_index];
+                // Database may return only partial results, i.e. not all dates
+                // for the range may be returned. Hence we need to check if the
+                // database result is for the same year month.
+                while summary.year != response_model_item.year
+                    || summary.month != response_model_item.month
+                {
+                    response_item_index += 1;
+                    response_model_item = &mut response_model.month_logs[response_item_index];
+                }
+
+                response_model_item.envoy_total_watts = summary.envoy_total_watts;
+                response_model_item.zever_total_watts = summary.zever_total_watts;
+                response_item_index += 1;
+            }
+
+            add_missing_entries_to_month_cache(&summaries, &month_cache);
+        }
+    }
 
     match serde_json::to_string(&response_model) {
         Ok(json) => json,
@@ -273,6 +356,153 @@ fn get_months_solar_json(
     }
 }
 
+fn get_month_summary_range_from_database(
+    start: &YearMonth,
+    stop: &YearMonth,
+    database_path: &str,
+) -> Vec<MonthsResponseItem> {
+    let mut results = Vec::new();
+    let summaries = database::get_month_solar_summaries(&start, &stop, &database_path);
+    for summary in summaries.iter() {
+        results.push(MonthsResponseItem {
+            year: summary.year,
+            month: summary.month,
+            envoy_total_watts: summary.envoy_total_watts,
+            zever_total_watts: summary.zever_total_watts,
+        });
+    }
+
+    return results;
+}
+
+fn get_cached_months_solar_json(
+    start: &YearMonth,
+    stop: &YearMonth,
+    month_cache: &std::sync::Arc<RwLock<Vec<CachedMonthsResponseItem>>>,
+) -> Vec<MonthsResponseItem> {
+    if let Ok(cache) = month_cache.read() {
+        let mut results = Vec::new();
+        for item in cache
+            .iter()
+            .filter(|i| i.year_month >= *start && i.year_month <= *stop)
+        {
+            results.push(MonthsResponseItem {
+                year: item.year_month.year,
+                month: item.year_month.month,
+                envoy_total_watts: item.envoy_total_watts,
+                zever_total_watts: item.zever_total_watts,
+            });
+        }
+
+        log::info!(
+            "Retrieved {} entries by month summary cache for {} to {} range",
+            results.len(),
+            start,
+            stop
+        );
+        return results;
+    } else {
+        log::error!("Failed to acquire read lock for month cache");
+        return Vec::new();
+    }
+}
+
+fn compact_missing_dates_to_ranges(missing_year_months: &[YearMonth]) -> Vec<YearMonthRange> {
+    let mut results = Vec::new();
+    if missing_year_months.len() < 1 {
+        return results;
+    }
+
+    let mut start_index = 0;
+    let mut current_year_month = missing_year_months[start_index].clone();
+    for (index, next_year_month) in missing_year_months.iter().skip(1).enumerate() {
+        if current_year_month.get_next_month() != *next_year_month {
+            results.push(
+                YearMonthRange::new(&missing_year_months[start_index], &current_year_month)
+                    .unwrap(),
+            );
+
+            start_index = index;
+        }
+
+        current_year_month = next_year_month.clone();
+    }
+
+    let maybe_last_result_entry = results.last();
+    if maybe_last_result_entry.is_none()
+        || maybe_last_result_entry.unwrap().stop() < *missing_year_months.last().unwrap()
+    {
+        results.push(
+            YearMonthRange::new(&missing_year_months[start_index], &current_year_month).unwrap(),
+        );
+    }
+
+    return results;
+}
+
+fn add_missing_entries_to_month_cache(
+    summaries: &[MonthsResponseItem],
+    month_cache: &RwLock<Vec<CachedMonthsResponseItem>>,
+) {
+    if summaries.len() < 1 {
+        return;
+    }
+
+    if let Ok(mut cache) = month_cache.write() {
+        let first_summary_year_month = YearMonth {
+            year: summaries[0].year,
+            month: summaries[0].month,
+        };
+        let mut summary_insertion_index = cache
+            .iter()
+            .enumerate()
+            .find_map(|(index, item)| {
+                if item.year_month > first_summary_year_month {
+                    return Some(index - 1);
+                }
+
+                return None;
+            })
+            .unwrap_or(0);
+        let current_year_month = YearMonth::today();
+
+        for summary in summaries.iter() {
+            let summary_year_month = YearMonth {
+                year: summary.year,
+                month: summary.month,
+            };
+            // Do not cache results that are subject to change, such as the
+            // current month or any future month
+            if summary_year_month >= current_year_month {
+                break;
+            }
+
+            let to_insert = CachedMonthsResponseItem {
+                year_month: summary_year_month,
+                envoy_total_watts: summary.envoy_total_watts,
+                zever_total_watts: summary.zever_total_watts,
+            };
+            if summary_insertion_index < cache.len() {
+                while cache[summary_insertion_index].year_month < summary_year_month {
+                    summary_insertion_index += 1;
+                }
+
+                if summary_insertion_index < cache.len() {
+                    cache.insert(summary_insertion_index, to_insert);
+                    summary_insertion_index += 1;
+                } else {
+                    cache.push(to_insert);
+                }
+            } else {
+                cache.push(to_insert);
+                summary_insertion_index += 1;
+            }
+        }
+    } else {
+        log::error!("Failed to acquire write lock for month cache");
+    }
+}
+
 #[derive(serde::Serialize)]
 #[serde(rename_all = "camelCase")]
 struct MonthsResponse {
@@ -287,3 +517,10 @@ struct MonthsResponseItem {
     envoy_total_watts: i32,
     zever_total_watts: i32,
 }
+
+#[derive(Clone)]
+struct CachedMonthsResponseItem {
+    year_month: YearMonth,
+    envoy_total_watts: i32,
+    zever_total_watts: i32,
+}