/**
 * Utility for inserting a block into a content array relative to tool_result
 * blocks. Used by the API layer to position supplementary content (e.g.,
 * cache editing directives) correctly within user messages.
 *
 * Placement rules:
 * - If tool_result blocks exist: insert after the last one
 * - Otherwise: insert before the last block
 * - If the inserted block would be the final element, a text continuation
 * block is appended (some APIs require the prompt not to end with
 * non-text content)
 */

/**
 * Inserts a block into the content array after the last tool_result block.
 * Mutates the array in place.
 *
 * @param content - The content array to modify
 * @param block - The block to insert
 */
export function insertBlockAfterToolResults(
 content: unknown[],
 block: unknown,
): void {
 // Find position after the last tool_result block
 let lastToolResultIndex = -1
 for (let i = 0; i < content.length; i++) {
 const item = content[i]
 if (
 item &&
 typeof item === 'object' &&
 'type' in item &&
 (item as { type: string }).type === 'tool_result'
 ) {
 lastToolResultIndex = i
 }
 }

 if (lastToolResultIndex >= 0) {
 const insertPos = lastToolResultIndex + 1
 content.splice(insertPos, 0, block)
 // Append a text continuation if the inserted block is now last
 if (insertPos === content.length - 1) {
 content.push({ type: 'text', text: '.' })
 }
 } else {
 // No tool_result blocks — insert before the last block
 const insertIndex = Math.max(0, content.length - 1)
 content.splice(insertIndex, 0, block)
 }
}