import { subscriptions, computeCid, type Subscription, type SubscriptionResult } from "./xrpc.ts";
import { type IndexerEvent } from "./indexer.ts";
import { getSafeField, matchDocAgainstQuery } from "./live-utils.ts";

interface ClientDelta {
  documents: Record<string, { cid: string; doc: Record<string, unknown> }>;
  queries: Record<string, { ecid: string; result: string[] }>;
}

function extractSortValues(doc: Record<string, any>, sortClause: any[]): unknown[] {
  const values: unknown[] = [];
  for (const sortField of sortClause) {
    const key = Object.keys(sortField)[0];
    const value = getSafeField(doc, key);
    values.push(value);
  }
  return values;
}

function compareItems(aSorts: unknown[], bSorts: unknown[], sortClause: any[]): number {
  for (let i = 0; i < sortClause.length; i++) {
    const direction = Object.values(sortClause[i])[0];
    const valA = aSorts[i];
    const valB = bSorts[i];

    if (valA === valB) continue;

    if (valA === undefined || valA === null) return 1;
    if (valB === undefined || valB === null) return -1;
    
    let comparison = 0;
    if (valA < valB) {
      comparison = -1;
    } else if (valA > valB) {
      comparison = 1;
    }
    
    if (comparison !== 0) {
      return direction === 'desc' ? -comparison : comparison;
    }
  }
  return 0;
}

function findInsertIndex(sortedArray: Subscription['result'], newItem: SubscriptionResult, sortClause: any[]): number {
    let low = 0;
    let high = sortedArray.length;

    while (low < high) {
        const mid = Math.floor((low + high) / 2);
        const comparison = compareItems(newItem.sortValues, sortedArray[mid].sortValues, sortClause);
        if (comparison < 0) {
            high = mid;
        } else {
            low = mid + 1;
        }
    }
    return low;
}

export async function processEventForSync(event: IndexerEvent) {
  const requiredDocuments = new Set<string>();
  
  const changedQueries: {
      queryId: string;
      newEcid: string;
      newRichResult: SubscriptionResult[]; 
      newResultUris: string[];
      sub: Subscription;
  }[] = [];

  for (const [queryId, sub] of subscriptions.entries()) {
    let newRichResult: SubscriptionResult[] | undefined = undefined;
    const sortClause = (sub.esQuery as any).sort;

    if (event.type === 'index') {
      const queryClause = (sub.esQuery as any).query ?? {};
      const doesMatch = matchDocAgainstQuery(event.data, queryClause);
      const currentIndex = sub.result.findIndex(item => item.uri === event.uri);
      const wasInResult = currentIndex !== -1;

      if (doesMatch && !wasInResult) {
        const newItem = {
          uri: event.uri,
          sortValues: extractSortValues(event.data, sortClause),
        };
        const insertIndex = findInsertIndex(sub.result, newItem, sortClause);
        
        newRichResult = [...sub.result];
        newRichResult.splice(insertIndex, 0, newItem);
        requiredDocuments.add(event.uri);

      } else if (!doesMatch && wasInResult) {
        newRichResult = sub.result.filter(item => item.uri !== event.uri);

      } else if (doesMatch && wasInResult) {
        const newItem = {
          uri: event.uri,
          sortValues: extractSortValues(event.data, sortClause),
        };
        if (compareItems(newItem.sortValues, sub.result[currentIndex].sortValues, sortClause) !== 0) {
            const tempResult = sub.result.filter(item => item.uri !== event.uri);
            const insertIndex = findInsertIndex(tempResult, newItem, sortClause);
            
            newRichResult = [...tempResult];
            newRichResult.splice(insertIndex, 0, newItem);
        }
        requiredDocuments.add(event.uri);
      }
    } else if (event.type === 'delete') {
      if (sub.result.some(item => item.uri === event.uri)) {
        newRichResult = sub.result.filter(item => item.uri !== event.uri);
      }
    }

    if (newRichResult) {
      const newResultUris = newRichResult.map(item => item.uri);
      const newEcid = await computeCid(newResultUris);
      
      if (newEcid !== sub.ecid) {
          changedQueries.push({
              queryId,
              newEcid,
              newRichResult,
              newResultUris,
              sub
          });
      }
    }
  }

  for (const { queryId, newEcid, newRichResult } of changedQueries) {
    const sub = subscriptions.get(queryId);
    if (sub) {
        sub.ecid = newEcid;
        sub.result = newRichResult;
    }
  }

  const documentsPayload: Record<string, { cid: string; doc: Record<string, unknown> }> = {};
  if (event.type === 'index') {
    for (const uri of requiredDocuments) {
        documentsPayload[uri] = {
            cid: event.data["$metadata.cid"] as string,
            doc: event.data as Record<string, unknown>,
        };
    }
  }

  if (changedQueries.length > 0 || Object.keys(documentsPayload).length > 0) {
    const affectedClients = new Set<WebSocket>();
    changedQueries.forEach(cq => cq.sub.clients.forEach(c => affectedClients.add(c)));
    
    if (Object.keys(documentsPayload).length > 0 && event.type === 'index') {
        for (const [, sub] of subscriptions.entries()) {
            if (sub.result.some(item => item.uri === event.uri)) {
                sub.clients.forEach(c => affectedClients.add(c));
            }
        }
    }

    for (const client of affectedClients) {
        const delta: ClientDelta = {
            documents: documentsPayload,
            queries: {},
        };

        for (const { queryId, newEcid, newResultUris, sub } of changedQueries) {
            if (sub.clients.has(client)) {
                delta.queries[queryId] = { ecid: newEcid, result: newResultUris };
            }
        }
        
        if (Object.keys(delta.queries).length > 0 || Object.keys(documentsPayload).length > 0) {
            if (client.readyState === WebSocket.OPEN) {
                try {
                    client.send(JSON.stringify({ type: 'query-delta', ...delta }));
                } catch (err) {
                    console.error("Failed to send delta to client:", err);
                }
            }
        }
    }
  }
}