static accumulateDelta()

in lib/AssistantStream.ts [723:803]
69 lines of code
22 McCabe index (conditional complexity)

  static accumulateDelta(
    acc: Record<string, any>,
    delta: Record<string, any>,
  ): Record<string, any> {
    for (const [key, deltaValue] of Object.entries(delta)) {
      if (!acc.hasOwnProperty(key)) {
        acc[key] = deltaValue;
        continue;
      }

      let accValue = acc[key];
      if (accValue === null || accValue === undefined) {
        acc[key] = deltaValue;
        continue;
      }

      // We don't accumulate these special properties
      if (key === "index" || key === "type") {
        acc[key] = deltaValue;
        continue;
      }

      // Type-specific accumulation logic
      if (typeof accValue === "string" && typeof deltaValue === "string") {
        accValue += deltaValue;
      } else if (
        typeof accValue === "number" && typeof deltaValue === "number"
      ) {
        accValue += deltaValue;
      } else if (Core.isObj(accValue) && Core.isObj(deltaValue)) {
        accValue = this.accumulateDelta(
          accValue as Record<string, any>,
          deltaValue as Record<string, any>,
        );
      } else if (Array.isArray(accValue) && Array.isArray(deltaValue)) {
        if (
          accValue.every((x) => typeof x === "string" || typeof x === "number")
        ) {
          accValue.push(...deltaValue); // Use spread syntax for efficient addition
          continue;
        }

        for (const deltaEntry of deltaValue) {
          if (!Core.isObj(deltaEntry)) {
            throw new Error(
              `Expected array delta entry to be an object but got: ${deltaEntry}`,
            );
          }

          const index = deltaEntry["index"];
          if (index == null) {
            console.error(deltaEntry);
            throw new Error(
              "Expected array delta entry to have an `index` property",
            );
          }

          if (typeof index !== "number") {
            throw new Error(
              `Expected array delta entry \`index\` property to be a number but got ${index}`,
            );
          }

          const accEntry = accValue[index];
          if (accEntry == null) {
            accValue.push(deltaEntry);
          } else {
            accValue[index] = this.accumulateDelta(accEntry, deltaEntry);
          }
        }
        continue;
      } else {
        throw Error(
          `Unhandled record type: ${key}, deltaValue: ${deltaValue}, accValue: ${accValue}`,
        );
      }
      acc[key] = accValue;
    }

    return acc;
  }