import type OpenAI from "openai";
import type {
	Tool as OpenAITool,
	ResponseCreateParamsStreaming,
	ResponseFunctionToolCall,
	ResponseInput,
	ResponseInputContent,
	ResponseInputImage,
	ResponseInputText,
	ResponseOutputMessage,
	ResponseReasoningItem,
	ResponseStreamEvent,
} from "openai/resources/responses/responses.js";
import { calculateCost } from "../models.js";
import type {
	Api,
	AssistantMessage,
	Context,
	ImageContent,
	Model,
	StopReason,
	TextContent,
	TextSignatureV1,
	ThinkingContent,
	Tool,
	ToolCall,
	Usage,
} from "../types.js";
import type { AssistantMessageEventStream } from "../utils/event-stream.js";
import { shortHash } from "../utils/hash.js";
import { parseStreamingJson } from "../utils/json-parse.js";
import { sanitizeSurrogates } from "../utils/sanitize-unicode.js";
import { transformMessages } from "./transform-messages.js";

// =============================================================================
// Utilities
// =============================================================================

function encodeTextSignatureV1(id: string, phase?: TextSignatureV1["phase"]): string {
	const payload: TextSignatureV1 = { v: 1, id };
	if (phase) payload.phase = phase;
	return JSON.stringify(payload);
}

function parseTextSignature(
	signature: string | undefined,
): { id: string; phase?: TextSignatureV1["phase"] } | undefined {
	if (!signature) return undefined;
	if (signature.startsWith("{")) {
		try {
			const parsed = JSON.parse(signature) as Partial<TextSignatureV1>;
			if (parsed.v === 1 && typeof parsed.id === "string") {
				if (parsed.phase === "commentary" || parsed.phase === "final_answer") {
					return { id: parsed.id, phase: parsed.phase };
				}
				return { id: parsed.id };
			}
		} catch {
			// Fall through to legacy plain-string handling.
		}
	}
	return { id: signature };
}

export interface OpenAIResponsesStreamOptions {
	serviceTier?: ResponseCreateParamsStreaming["service_tier"];
	applyServiceTierPricing?: (
		usage: Usage,
		serviceTier: ResponseCreateParamsStreaming["service_tier"] | undefined,
	) => void;
}

export interface ConvertResponsesMessagesOptions {
	includeSystemPrompt?: boolean;
}

export interface ConvertResponsesToolsOptions {
	strict?: boolean | null;
}

// =============================================================================
// Message conversion
// =============================================================================

export function convertResponsesMessages<TApi extends Api>(
	model: Model<TApi>,
	context: Context,
	allowedToolCallProviders: ReadonlySet<string>,
	options?: ConvertResponsesMessagesOptions,
): ResponseInput {
	const messages: ResponseInput = [];

	const normalizeToolCallId = (id: string): string => {
		if (!allowedToolCallProviders.has(model.provider)) return id;
		if (!id.includes("|")) return id;
		const [callId, itemId] = id.split("|");
		const sanitizedCallId = callId.replace(/[^a-zA-Z0-9_-]/g, "_");
		let sanitizedItemId = itemId.replace(/[^a-zA-Z0-9_-]/g, "_");
		// OpenAI Responses API requires item id to start with "fc"
		if (!sanitizedItemId.startsWith("fc")) {
			sanitizedItemId = `fc_${sanitizedItemId}`;
		}
		// Truncate to 64 chars and strip trailing underscores (OpenAI Codex rejects them)
		let normalizedCallId = sanitizedCallId.length > 64 ? sanitizedCallId.slice(0, 64) : sanitizedCallId;
		let normalizedItemId = sanitizedItemId.length > 64 ? sanitizedItemId.slice(0, 64) : sanitizedItemId;
		normalizedCallId = normalizedCallId.replace(/_+$/, "");
		normalizedItemId = normalizedItemId.replace(/_+$/, "");
		return `${normalizedCallId}|${normalizedItemId}`;
	};

	const transformedMessages = transformMessages(context.messages, model, normalizeToolCallId);

	const includeSystemPrompt = options?.includeSystemPrompt ?? true;
	if (includeSystemPrompt && context.systemPrompt) {
		const role = model.reasoning ? "developer" : "system";
		messages.push({
			role,
			content: sanitizeSurrogates(context.systemPrompt),
		});
	}

	let msgIndex = 0;
	for (const msg of transformedMessages) {
		if (msg.role === "user") {
			if (typeof msg.content === "string") {
				messages.push({
					role: "user",
					content: [{ type: "input_text", text: sanitizeSurrogates(msg.content) }],
				});
			} else {
				const content: ResponseInputContent[] = msg.content.map((item): ResponseInputContent => {
					if (item.type === "text") {
						return {
							type: "input_text",
							text: sanitizeSurrogates(item.text),
						} satisfies ResponseInputText;
					}
					return {
						type: "input_image",
						detail: "auto",
						image_url: `data:${item.mimeType};base64,${item.data}`,
					} satisfies ResponseInputImage;
				});
				const filteredContent = !model.input.includes("image")
					? content.filter((c) => c.type !== "input_image")
					: content;
				if (filteredContent.length === 0) continue;
				messages.push({
					role: "user",
					content: filteredContent,
				});
			}
		} else if (msg.role === "assistant") {
			const output: ResponseInput = [];
			const assistantMsg = msg as AssistantMessage;
			const isDifferentModel =
				assistantMsg.model !== model.id &&
				assistantMsg.provider === model.provider &&
				assistantMsg.api === model.api;

			for (const block of msg.content) {
				if (block.type === "thinking") {
					if (block.thinking.trim().length === 0) continue;
					if (block.thinkingSignature) {
						const reasoningItem = JSON.parse(block.thinkingSignature) as ResponseReasoningItem;
						output.push(reasoningItem);
					}
				} else if (block.type === "text") {
					const textBlock = block as TextContent;
					const parsedSignature = parseTextSignature(textBlock.textSignature);
					// OpenAI requires id to be max 64 characters
					let msgId = parsedSignature?.id;
					if (!msgId) {
						msgId = `msg_${msgIndex}`;
					} else if (msgId.length > 64) {
						msgId = `msg_${shortHash(msgId)}`;
					}
					output.push({
						type: "message",
						role: "assistant",
						content: [{ type: "output_text", text: sanitizeSurrogates(textBlock.text), annotations: [] }],
						status: "completed",
						id: msgId,
						phase: parsedSignature?.phase,
					} satisfies ResponseOutputMessage);
				} else if (block.type === "toolCall") {
					const toolCall = block as ToolCall;
					const [callId, itemIdRaw] = toolCall.id.split("|");
					let itemId: string | undefined = itemIdRaw;

					// For different-model messages, set id to undefined to avoid pairing validation.
					// OpenAI tracks which fc_xxx IDs were paired with rs_xxx reasoning items.
					// By omitting the id, we avoid triggering that validation (like cross-provider does).
					if (isDifferentModel && itemId?.startsWith("fc_")) {
						itemId = undefined;
					}

					output.push({
						type: "function_call",
						id: itemId,
						call_id: callId,
						name: toolCall.name,
						arguments: JSON.stringify(toolCall.arguments),
					});
				}
			}
			if (output.length === 0) continue;
			messages.push(...output);
		} else if (msg.role === "toolResult") {
			// Extract text and image content
			const textResult = msg.content
				.filter((c): c is TextContent => c.type === "text")
				.map((c) => c.text)
				.join("\n");
			const hasImages = msg.content.some((c): c is ImageContent => c.type === "image");

			// Always send function_call_output with text (or placeholder if only images)
			const hasText = textResult.length > 0;
			const [callId] = msg.toolCallId.split("|");
			messages.push({
				type: "function_call_output",
				call_id: callId,
				output: sanitizeSurrogates(hasText ? textResult : "(see attached image)"),
			});

			// If there are images and model supports them, send a follow-up user message with images
			if (hasImages && model.input.includes("image")) {
				const contentParts: ResponseInputContent[] = [];

				// Add text prefix
				contentParts.push({
					type: "input_text",
					text: "Attached image(s) from tool result:",
				} satisfies ResponseInputText);

				// Add images
				for (const block of msg.content) {
					if (block.type === "image") {
						contentParts.push({
							type: "input_image",
							detail: "auto",
							image_url: `data:${block.mimeType};base64,${block.data}`,
						} satisfies ResponseInputImage);
					}
				}

				messages.push({
					role: "user",
					content: contentParts,
				});
			}
		}
		msgIndex++;
	}

	return messages;
}

// =============================================================================
// Tool conversion
// =============================================================================

export function convertResponsesTools(tools: Tool[], options?: ConvertResponsesToolsOptions): OpenAITool[] {
	const strict = options?.strict === undefined ? false : options.strict;
	return tools.map((tool) => ({
		type: "function",
		name: tool.name,
		description: tool.description,
		parameters: tool.parameters as any, // TypeBox already generates JSON Schema
		strict,
	}));
}

// =============================================================================
// Stream processing
// =============================================================================

export async function processResponsesStream<TApi extends Api>(
	openaiStream: AsyncIterable<ResponseStreamEvent>,
	output: AssistantMessage,
	stream: AssistantMessageEventStream,
	model: Model<TApi>,
	options?: OpenAIResponsesStreamOptions,
): Promise<void> {
	let currentItem: ResponseReasoningItem | ResponseOutputMessage | ResponseFunctionToolCall | null = null;
	let currentBlock: ThinkingContent | TextContent | (ToolCall & { partialJson: string }) | null = null;
	const blocks = output.content;
	const blockIndex = () => blocks.length - 1;

	for await (const event of openaiStream) {
		if (event.type === "response.output_item.added") {
			const item = event.item;
			if (item.type === "reasoning") {
				currentItem = item;
				currentBlock = { type: "thinking", thinking: "" };
				output.content.push(currentBlock);
				stream.push({ type: "thinking_start", contentIndex: blockIndex(), partial: output });
			} else if (item.type === "message") {
				currentItem = item;
				currentBlock = { type: "text", text: "" };
				output.content.push(currentBlock);
				stream.push({ type: "text_start", contentIndex: blockIndex(), partial: output });
			} else if (item.type === "function_call") {
				currentItem = item;
				currentBlock = {
					type: "toolCall",
					id: `${item.call_id}|${item.id}`,
					name: item.name,
					arguments: {},
					partialJson: item.arguments || "",
				};
				output.content.push(currentBlock);
				stream.push({ type: "toolcall_start", contentIndex: blockIndex(), partial: output });
			}
		} else if (event.type === "response.reasoning_summary_part.added") {
			if (currentItem && currentItem.type === "reasoning") {
				currentItem.summary = currentItem.summary || [];
				currentItem.summary.push(event.part);
			}
		} else if (event.type === "response.reasoning_summary_text.delta") {
			if (currentItem?.type === "reasoning" && currentBlock?.type === "thinking") {
				currentItem.summary = currentItem.summary || [];
				const lastPart = currentItem.summary[currentItem.summary.length - 1];
				if (lastPart) {
					currentBlock.thinking += event.delta;
					lastPart.text += event.delta;
					stream.push({
						type: "thinking_delta",
						contentIndex: blockIndex(),
						delta: event.delta,
						partial: output,
					});
				}
			}
		} else if (event.type === "response.reasoning_summary_part.done") {
			if (currentItem?.type === "reasoning" && currentBlock?.type === "thinking") {
				currentItem.summary = currentItem.summary || [];
				const lastPart = currentItem.summary[currentItem.summary.length - 1];
				if (lastPart) {
					currentBlock.thinking += "\n\n";
					lastPart.text += "\n\n";
					stream.push({
						type: "thinking_delta",
						contentIndex: blockIndex(),
						delta: "\n\n",
						partial: output,
					});
				}
			}
		} else if (event.type === "response.content_part.added") {
			if (currentItem?.type === "message") {
				currentItem.content = currentItem.content || [];
				// Filter out ReasoningText, only accept output_text and refusal
				if (event.part.type === "output_text" || event.part.type === "refusal") {
					currentItem.content.push(event.part);
				}
			}
		} else if (event.type === "response.output_text.delta") {
			if (currentItem?.type === "message" && currentBlock?.type === "text") {
				if (!currentItem.content || currentItem.content.length === 0) {
					continue;
				}
				const lastPart = currentItem.content[currentItem.content.length - 1];
				if (lastPart?.type === "output_text") {
					currentBlock.text += event.delta;
					lastPart.text += event.delta;
					stream.push({
						type: "text_delta",
						contentIndex: blockIndex(),
						delta: event.delta,
						partial: output,
					});
				}
			}
		} else if (event.type === "response.refusal.delta") {
			if (currentItem?.type === "message" && currentBlock?.type === "text") {
				if (!currentItem.content || currentItem.content.length === 0) {
					continue;
				}
				const lastPart = currentItem.content[currentItem.content.length - 1];
				if (lastPart?.type === "refusal") {
					currentBlock.text += event.delta;
					lastPart.refusal += event.delta;
					stream.push({
						type: "text_delta",
						contentIndex: blockIndex(),
						delta: event.delta,
						partial: output,
					});
				}
			}
		} else if (event.type === "response.function_call_arguments.delta") {
			if (currentItem?.type === "function_call" && currentBlock?.type === "toolCall") {
				currentBlock.partialJson += event.delta;
				currentBlock.arguments = parseStreamingJson(currentBlock.partialJson);
				stream.push({
					type: "toolcall_delta",
					contentIndex: blockIndex(),
					delta: event.delta,
					partial: output,
				});
			}
		} else if (event.type === "response.function_call_arguments.done") {
			if (currentItem?.type === "function_call" && currentBlock?.type === "toolCall") {
				currentBlock.partialJson = event.arguments;
				currentBlock.arguments = parseStreamingJson(currentBlock.partialJson);
			}
		} else if (event.type === "response.output_item.done") {
			const item = event.item;

			if (item.type === "reasoning" && currentBlock?.type === "thinking") {
				currentBlock.thinking = item.summary?.map((s) => s.text).join("\n\n") || "";
				currentBlock.thinkingSignature = JSON.stringify(item);
				stream.push({
					type: "thinking_end",
					contentIndex: blockIndex(),
					content: currentBlock.thinking,
					partial: output,
				});
				currentBlock = null;
			} else if (item.type === "message" && currentBlock?.type === "text") {
				currentBlock.text = item.content.map((c) => (c.type === "output_text" ? c.text : c.refusal)).join("");
				currentBlock.textSignature = encodeTextSignatureV1(item.id, item.phase ?? undefined);
				stream.push({
					type: "text_end",
					contentIndex: blockIndex(),
					content: currentBlock.text,
					partial: output,
				});
				currentBlock = null;
			} else if (item.type === "function_call") {
				const args =
					currentBlock?.type === "toolCall" && currentBlock.partialJson
						? parseStreamingJson(currentBlock.partialJson)
						: parseStreamingJson(item.arguments || "{}");
				const toolCall: ToolCall = {
					type: "toolCall",
					id: `${item.call_id}|${item.id}`,
					name: item.name,
					arguments: args,
				};

				currentBlock = null;
				stream.push({ type: "toolcall_end", contentIndex: blockIndex(), toolCall, partial: output });
			}
		} else if (event.type === "response.completed") {
			const response = event.response;
			if (response?.usage) {
				const cachedTokens = response.usage.input_tokens_details?.cached_tokens || 0;
				output.usage = {
					// OpenAI includes cached tokens in input_tokens, so subtract to get non-cached input
					input: (response.usage.input_tokens || 0) - cachedTokens,
					output: response.usage.output_tokens || 0,
					cacheRead: cachedTokens,
					cacheWrite: 0,
					totalTokens: response.usage.total_tokens || 0,
					cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
				};
			}
			calculateCost(model, output.usage);
			if (options?.applyServiceTierPricing) {
				const serviceTier = response?.service_tier ?? options.serviceTier;
				options.applyServiceTierPricing(output.usage, serviceTier);
			}
			// Map status to stop reason
			output.stopReason = mapStopReason(response?.status);
			if (output.content.some((b) => b.type === "toolCall") && output.stopReason === "stop") {
				output.stopReason = "toolUse";
			}
		} else if (event.type === "error") {
			throw new Error(`Error Code ${event.code}: ${event.message}` || "Unknown error");
		} else if (event.type === "response.failed") {
			throw new Error("Unknown error");
		}
	}
}

function mapStopReason(status: OpenAI.Responses.ResponseStatus | undefined): StopReason {
	if (!status) return "stop";
	switch (status) {
		case "completed":
			return "stop";
		case "incomplete":
			return "length";
		case "failed":
		case "cancelled":
			return "error";
		// These two are wonky ...
		case "in_progress":
		case "queued":
			return "stop";
		default: {
			const _exhaustive: never = status;
			throw new Error(`Unhandled stop reason: ${_exhaustive}`);
		}
	}
}