feat: first back recording and display (#12)

Record first backs, group them by item sets and show the most popular ones, with gold and %, in the frontend.

match_collector/src/champion_stat.ts

@@ -12,6 +12,13 @@ import {
   treeDeriveTags
 } from './item_tree'
 import { PLATFORM_KEYS } from './platform'
+import {
+  initItemDict as initFirstBackItemDict,
+  extractFirstBackFromMatch,
+  groupFirstBacksByItemSet,
+  FirstBackData,
+  FirstBackGroup
+} from './first_back'
 
 import { Match, Timeline, Participant, Frame } from './api'
 
@@ -65,6 +72,9 @@ type Build = {
   suppItems: Array<{ data: number; count: number }>
   boots: Array<{ data: number; count: number }>
   pickrate?: number
+  // First back data (collected during processing, grouped in finalize)
+  firstBacksRaw?: FirstBackData[]
+  firstBacks?: FirstBackGroup[]
 }
 
 type BuildWithStartItems = {
@@ -78,6 +88,8 @@ type BuildWithStartItems = {
   suppItems: Array<{ data: number; count: number }>
   boots: Array<{ data: number; count: number }>
   pickrate?: number
+  firstBacksRaw?: FirstBackData[]
+  firstBacks?: FirstBackGroup[]
 }
 
 type Builds = Build[]
@@ -225,7 +237,7 @@ function handleMatchBuilds(
   participantIndex: number,
   builds: Builds,
   platform?: string
-) {
+): Build {
   const timeline: Timeline = match.timeline
 
   // Find or create the build for this participant's rune configuration
@@ -316,6 +328,8 @@ function handleMatchBuilds(
   if (items.length > 0) {
     treeMerge(build.items, items)
   }
+
+  return build
 }
 
 function handleMatch(match: Match, champions: Map<number, ChampionData>, platform?: string) {
@@ -411,7 +425,16 @@ function handleMatch(match: Match, champions: Map<number, ChampionData>, platfor
     }
 
     // Items and runes (builds)
-    handleMatchBuilds(match, participant, participantIndex, lane.builds, platform)
+    const build = handleMatchBuilds(match, participant, participantIndex, lane.builds, platform)
+
+    // First back data - store at build level
+    const firstBackData = extractFirstBackFromMatch(match, participantIndex)
+    if (firstBackData) {
+      if (!build.firstBacksRaw) {
+        build.firstBacksRaw = []
+      }
+      build.firstBacksRaw.push(firstBackData)
+    }
   }
 }
 
@@ -473,7 +496,8 @@ function splitMergeOnStarterItem(build: Build, championName: string): BuildWithS
         startItems,
         suppItems: build.suppItems,
         boots: build.boots,
-        pickrate: build.pickrate
+        pickrate: build.pickrate,
+        firstBacksRaw: build.firstBacksRaw
       }
     ]
   } else {
@@ -489,7 +513,8 @@ function splitMergeOnStarterItem(build: Build, championName: string): BuildWithS
         count: c.count,
         startItems: [{ data: c.data!, count: c.count }],
         suppItems: build.suppItems,
-        boots: build.boots
+        boots: build.boots,
+        firstBacksRaw: build.firstBacksRaw
       })
       c.data = undefined
     }
@@ -573,6 +598,14 @@ function mergeBuildsForRunes(builds: BuildWithStartItems[]): BuildWithStartItems
     const runes = Array.from(runesMap.values())
     runes.sort((a, b) => b.count - a.count)
 
+    // Merge first backs raw data
+    const firstBacksRaw: FirstBackData[] = []
+    for (const build of allSimilarBuilds) {
+      if (build.firstBacksRaw) {
+        firstBacksRaw.push(...build.firstBacksRaw)
+      }
+    }
+
     merged.push({
       runeKeystone: runes[0].selections[0],
       runes: runes,
@@ -581,7 +614,8 @@ function mergeBuildsForRunes(builds: BuildWithStartItems[]): BuildWithStartItems
       count: totalCount,
       startItems: mergeItemCounts(allSimilarBuilds, b => b.startItems),
       suppItems: mergeItemCounts(allSimilarBuilds, b => b.suppItems),
-      boots: mergeItemCounts(allSimilarBuilds, b => b.boots)
+      boots: mergeItemCounts(allSimilarBuilds, b => b.boots),
+      firstBacksRaw: firstBacksRaw.length > 0 ? firstBacksRaw : undefined
     })
   }
 
@@ -659,6 +693,19 @@ async function finalizeChampionStats(champion: ChampionData, totalMatches: numbe
     // all along.
     lane.builds = mergeBuildsForRunes(lane.builds as BuildWithStartItems[])
     cleanupLaneBuilds(lane)
+
+    // Process first backs at build level - group by item set
+    for (const build of lane.builds) {
+      if (build.firstBacksRaw && build.firstBacksRaw.length > 0) {
+        build.firstBacks = groupFirstBacksByItemSet(build.firstBacksRaw)
+        // Keep only top 7 groups
+        if (build.firstBacks!.length > 7) {
+          build.firstBacks = build.firstBacks!.slice(0, 7)
+        }
+        // Clean up raw data to save space
+        delete build.firstBacksRaw
+      }
+    }
   }
 
   for (const lane of champion.lanes) {
@@ -723,6 +770,9 @@ async function makeChampionsStats(client: MongoClient, patch: string, platforms:
     itemDict.set(item.id, item)
   }
 
+  // Initialize first back item dictionary
+  await initFirstBackItemDict()
+
   const list = await championList()
   console.log('Generating stats for ' + list.length + ' champions')