import type { DynamicParallelStep, ParallelTaskItem } from "../../shared/settings.ts";
import type { ArtifactPaths, ChainOutputMap, JsonSchemaObject, SingleResult } from "../../shared/types.ts";
import { getSingleResultOutput } from "../../shared/utils.ts";
import { validateStructuredOutputValue } from "./structured-output.ts";

export class DynamicFanoutError extends Error {}

export interface DynamicFanoutConfig {
	maxItems?: number;
	allowRunnerFields?: boolean;
}

export interface DynamicMaterializedItem {
	index: number;
	key: string;
	idKey: string;
	item: unknown;
}

export interface DynamicCollectedResult {
	key: string;
	index: number;
	item: unknown;
	agent: string;
	exitCode: number | null;
	text: string;
	structured?: unknown;
	error?: string;
	timedOut?: boolean;
	outputPath?: string;
	artifactPaths?: ArtifactPaths;
}

export interface DynamicMaterializedGroup {
	items: DynamicMaterializedItem[];
	parallel: ParallelTaskItem[];
	collectedOnEmpty?: DynamicCollectedResult[];
}

const SAFE_OUTPUT_NAME_PATTERN = /^[A-Za-z_][A-Za-z0-9_]*$/;
const ITEM_NAME_PATTERN = /^[A-Za-z_][A-Za-z0-9_]*$/;
const ITEM_REF_PATTERN = /\{([A-Za-z_][A-Za-z0-9_]*)(?:\.([^{}]+))?\}/g;
const RESERVED_TEMPLATE_NAMES = new Set(["task", "previous", "chain_dir", "outputs"]);
const DYNAMIC_STEP_KEYS = new Set(["expand", "parallel", "collect", "concurrency", "failFast", "phase", "label", "acceptance"]);
const RUNNER_DYNAMIC_STEP_KEYS = new Set([...DYNAMIC_STEP_KEYS, "effectiveAcceptance", "sessionFiles", "thinkingOverrides"]);
const DYNAMIC_EXPAND_KEYS = new Set(["from", "item", "key", "maxItems", "onEmpty"]);
const DYNAMIC_EXPAND_FROM_KEYS = new Set(["output", "path"]);
const DYNAMIC_PARALLEL_KEYS = new Set(["agent", "task", "phase", "label", "outputSchema", "cwd", "output", "outputMode", "reads", "progress", "skill", "model", "toolBudget", "acceptance"]);
const RUNNER_DYNAMIC_PARALLEL_KEYS = new Set([
	...DYNAMIC_PARALLEL_KEYS,
	"outputName", "structured", "inheritProjectContext", "inheritSkills", "skills", "outputPath", "maxSubagentDepth",
	"structuredOutput", "structuredOutputSchema", "tools", "extensions", "subagentOnlyExtensions", "mcpDirectTools", "completionGuard", "systemPrompt",
	"systemPromptMode", "thinking", "modelCandidates", "sessionFile", "effectiveAcceptance", "parentSessionId",
]);
const DYNAMIC_COLLECT_KEYS = new Set(["as", "outputSchema"]);

export function isSafeOutputName(name: string): boolean {
	return SAFE_OUTPUT_NAME_PATTERN.test(name);
}

export function assertJsonPointer(pointer: string, label: string): void {
	if (pointer === "") return;
	if (!pointer.startsWith("/")) {
		throw new DynamicFanoutError(`${label} must be a JSON Pointer starting with '/'.`);
	}
	for (const segment of pointer.slice(1).split("/")) {
		if (/~(?![01])/.test(segment)) {
			throw new DynamicFanoutError(`${label} contains invalid JSON Pointer escape.`);
		}
	}
}

function decodePointerSegment(segment: string): string {
	return segment.replace(/~1/g, "/").replace(/~0/g, "~");
}

export function resolveJsonPointer(value: unknown, pointer: string, label: string): unknown {
	assertJsonPointer(pointer, label);
	if (pointer === "") return value;
	let current = value;
	for (const rawSegment of pointer.slice(1).split("/")) {
		const segment = decodePointerSegment(rawSegment);
		if (Array.isArray(current)) {
			if (!/^(0|[1-9][0-9]*)$/.test(segment)) {
				throw new DynamicFanoutError(`${label} segment '${segment}' does not address an array index.`);
			}
			const index = Number(segment);
			if (index >= current.length) throw new DynamicFanoutError(`${label} does not exist.`);
			current = current[index];
			continue;
		}
		if (!current || typeof current !== "object") {
			throw new DynamicFanoutError(`${label} does not exist.`);
		}
		const record = current as Record<string, unknown>;
		if (!Object.prototype.hasOwnProperty.call(record, segment)) {
			throw new DynamicFanoutError(`${label} does not exist.`);
		}
		current = record[segment];
	}
	return current;
}

function scalarToKey(value: unknown, label: string): string {
	if (typeof value === "string" || typeof value === "number" || typeof value === "boolean") {
		const key = String(value);
		if (!key.trim()) throw new DynamicFanoutError(`${label} resolved to an empty key.`);
		if (/[\u0000-\u001F\u007F]/.test(key)) throw new DynamicFanoutError(`${label} resolved to an unsafe key.`);
		if (key.length > 200) throw new DynamicFanoutError(`${label} resolved to a key longer than 200 characters.`);
		return key;
	}
	throw new DynamicFanoutError(`${label} must resolve to a string, number, or boolean.`);
}

export function normalizeItemKeyForId(key: string): string {
	const normalized = key
		.toLowerCase()
		.replace(/[^a-z0-9]+/g, "-")
		.replace(/^-+|-+$/g, "")
		.slice(0, 80);
	return normalized || "item";
}

function valueToTemplateText(value: unknown, reference: string): string {
	if (value === undefined) throw new DynamicFanoutError(`Unresolved item reference '${reference}'.`);
	if (typeof value === "string") return value;
	if (typeof value === "number" || typeof value === "boolean" || value === null) return String(value);
	return JSON.stringify(value);
}

function resolveItemPath(item: unknown, pathText: string | undefined, reference: string): unknown {
	if (!pathText) return item;
	const pointer = `/${pathText.split(".").map((segment) => segment.replace(/~/g, "~0").replace(/\//g, "~1")).join("/")}`;
	return resolveJsonPointer(item, pointer, reference);
}

export function resolveItemTemplate(template: string, itemName: string, item: unknown): string {
	return template.replace(ITEM_REF_PATTERN, (raw, name: string, pathText: string | undefined) => {
		if (name !== itemName) return raw;
		if (pathText !== undefined && (!pathText.trim() || pathText.includes(".."))) {
			throw new DynamicFanoutError(`Invalid item reference '${raw}'.`);
		}
		return valueToTemplateText(resolveItemPath(item, pathText, raw), raw);
	});
}

function assertOnlyKeys(value: unknown, allowed: Set<string>, label: string): void {
	if (!value || typeof value !== "object" || Array.isArray(value)) throw new DynamicFanoutError(`${label} must be an object.`);
	for (const key of Object.keys(value)) {
		if (!allowed.has(key)) throw new DynamicFanoutError(`${label} does not support field '${key}'.`);
	}
}

export function assertNoUnresolvedItemReferences(template: string, itemName: string, label: string): void {
	for (const match of template.matchAll(/\{([^{}]*)\}/g)) {
		const raw = match[0]!;
		const reference = match[1]!;
		if (reference === itemName || reference.startsWith(`${itemName}.`)) {
			if (!ITEM_REF_PATTERN.test(raw) || reference === `${itemName}.` || reference.includes("..")) {
				throw new DynamicFanoutError(`Invalid item reference '${raw}' in ${label}.`);
			}
			ITEM_REF_PATTERN.lastIndex = 0;
			continue;
		}
		ITEM_REF_PATTERN.lastIndex = 0;
		const name = reference.match(/^[A-Za-z_][A-Za-z0-9_]*/)?.[0];
		if (name === itemName) throw new DynamicFanoutError(`Invalid item reference '${raw}' in ${label}.`);
		if (name && RESERVED_TEMPLATE_NAMES.has(name)) continue;
		if (name) throw new DynamicFanoutError(`Unsupported template reference '${raw}' in ${label}.`);
	}
	ITEM_REF_PATTERN.lastIndex = 0;
	if (template.includes(`{${itemName}.}`) || new RegExp(`\\{${itemName}(?:\\.|$)[^}]*$`).test(template)) {
		throw new DynamicFanoutError(`Invalid item reference in ${label}.`);
	}
}

export function hasDynamicFanoutFields(step: unknown): boolean {
	return !!step && typeof step === "object" && !Array.isArray(step)
		&& (Object.prototype.hasOwnProperty.call(step, "expand") || Object.prototype.hasOwnProperty.call(step, "collect"));
}

export function validateDynamicStepShape(step: DynamicParallelStep, stepIndex: number, config: DynamicFanoutConfig = {}): void {
	const prefix = `Dynamic chain step ${stepIndex + 1}`;
	assertOnlyKeys(step, config.allowRunnerFields ? RUNNER_DYNAMIC_STEP_KEYS : DYNAMIC_STEP_KEYS, prefix);
	if (!step.expand || !step.expand.from) throw new DynamicFanoutError(`${prefix} requires expand.from.`);
	assertOnlyKeys(step.expand, DYNAMIC_EXPAND_KEYS, `${prefix} expand`);
	assertOnlyKeys(step.expand.from, DYNAMIC_EXPAND_FROM_KEYS, `${prefix} expand.from`);
	if (!isSafeOutputName(step.expand.from.output)) throw new DynamicFanoutError(`${prefix} has invalid expand.from.output '${step.expand.from.output}'.`);
	assertJsonPointer(step.expand.from.path, `${prefix} expand.from.path`);
	if (step.expand.key !== undefined) assertJsonPointer(step.expand.key, `${prefix} expand.key`);
	const itemName = step.expand.item ?? "item";
	if (!ITEM_NAME_PATTERN.test(itemName)) throw new DynamicFanoutError(`${prefix} has invalid expand.item '${itemName}'.`);
	if (step.expand.maxItems === undefined && config.maxItems === undefined) {
		throw new DynamicFanoutError(`${prefix} requires expand.maxItems or config.chain.dynamicFanout.maxItems.`);
	}
	if (step.expand.maxItems !== undefined && (!Number.isInteger(step.expand.maxItems) || step.expand.maxItems < 0)) {
		throw new DynamicFanoutError(`${prefix} expand.maxItems must be an integer >= 0.`);
	}
	if (config.maxItems !== undefined && (!Number.isInteger(config.maxItems) || config.maxItems < 0)) {
		throw new DynamicFanoutError("config.chain.dynamicFanout.maxItems must be an integer >= 0.");
	}
	if (!step.parallel || Array.isArray(step.parallel)) throw new DynamicFanoutError(`${prefix} requires a single parallel template object and cannot mix dynamic expand/collect with static parallel arrays.`);
	assertOnlyKeys(step.parallel, config.allowRunnerFields ? RUNNER_DYNAMIC_PARALLEL_KEYS : DYNAMIC_PARALLEL_KEYS, `${prefix} parallel`);
	if ("expand" in (step.parallel as object)) throw new DynamicFanoutError(`${prefix} does not support nested dynamic fanout.`);
	if (!step.parallel.agent) throw new DynamicFanoutError(`${prefix} parallel.agent is required.`);
	if (!step.collect?.as || !isSafeOutputName(step.collect.as)) throw new DynamicFanoutError(`${prefix} requires collect.as with a safe output name.`);
	assertOnlyKeys(step.collect, DYNAMIC_COLLECT_KEYS, `${prefix} collect`);
	for (const [label, template] of [
		["parallel.task", step.parallel.task],
		["parallel.label", step.parallel.label],
	] as const) {
		if (template) assertNoUnresolvedItemReferences(template, itemName, `${prefix} ${label}`);
	}
}

export function resolveDynamicFanoutItems(step: DynamicParallelStep, outputs: ChainOutputMap, stepIndex: number, config: DynamicFanoutConfig = {}): DynamicMaterializedItem[] {
	validateDynamicStepShape(step, stepIndex, config);
	const sourceName = step.expand.from.output;
	const source = outputs[sourceName];
	if (!source) throw new DynamicFanoutError(`Dynamic chain step ${stepIndex + 1} references unknown output '${sourceName}'.`);
	if (source.structured === undefined) throw new DynamicFanoutError(`Dynamic chain step ${stepIndex + 1} requires structured output '${sourceName}'.`);
	const value = resolveJsonPointer(source.structured, step.expand.from.path, `Dynamic chain step ${stepIndex + 1} expand.from.path`);
	if (!Array.isArray(value)) throw new DynamicFanoutError(`Dynamic chain step ${stepIndex + 1} expand.from.path must resolve to an array.`);
	const maxItems = step.expand.maxItems ?? config.maxItems;
	if (maxItems === undefined) throw new DynamicFanoutError(`Dynamic chain step ${stepIndex + 1} requires an effective maxItems.`);
	if (value.length > maxItems) throw new DynamicFanoutError(`Dynamic chain step ${stepIndex + 1} resolved ${value.length} items, exceeding maxItems ${maxItems}.`);
	const seen = new Set<string>();
	const seenIds = new Set<string>();
	return value.map((item, index) => {
		const key = step.expand.key === undefined
			? String(index)
			: scalarToKey(resolveJsonPointer(item, step.expand.key, `Dynamic chain step ${stepIndex + 1} expand.key`), `Dynamic chain step ${stepIndex + 1} expand.key`);
		if (seen.has(key)) throw new DynamicFanoutError(`Dynamic chain step ${stepIndex + 1} produced duplicate item key '${key}'.`);
		seen.add(key);
		const idKey = normalizeItemKeyForId(key);
		if (seenIds.has(idKey)) throw new DynamicFanoutError(`Dynamic chain step ${stepIndex + 1} produced colliding item id '${idKey}'.`);
		seenIds.add(idKey);
		return { index, key, idKey, item };
	});
}

export function materializeDynamicParallelStep(step: DynamicParallelStep, outputs: ChainOutputMap, stepIndex: number, config: DynamicFanoutConfig = {}): DynamicMaterializedGroup {
	const items = resolveDynamicFanoutItems(step, outputs, stepIndex, config);
	if (items.length === 0) {
		if ((step.expand.onEmpty ?? "skip") === "fail") {
			throw new DynamicFanoutError(`Dynamic chain step ${stepIndex + 1} source array is empty.`);
		}
		return { items, parallel: [], collectedOnEmpty: [] };
	}
	const itemName = step.expand.item ?? "item";
	const parallel = items.map((entry) => {
		const task = resolveItemTemplate(step.parallel.task ?? "{previous}", itemName, entry.item);
		const label = step.parallel.label ? resolveItemTemplate(step.parallel.label, itemName, entry.item) : undefined;
		return {
			...step.parallel,
			task,
			...(label !== undefined ? { label } : {}),
		};
	});
	return { items, parallel };
}

export function collectDynamicResults(
	step: DynamicParallelStep,
	items: DynamicMaterializedItem[],
	results: Array<Pick<SingleResult, "agent" | "exitCode" | "error" | "timedOut" | "structuredOutput" | "artifactPaths" | "savedOutputPath"> & { output?: string; finalOutput?: string }>,
): DynamicCollectedResult[] {
	return items.map((entry, index) => {
		const result = results[index];
		const text = result
			? ("output" in result && typeof result.output === "string" ? result.output : getSingleResultOutput(result as SingleResult))
			: "";
		return {
			key: entry.key,
			index: entry.index,
			item: entry.item,
			agent: result?.agent ?? step.parallel.agent,
			exitCode: result?.exitCode ?? null,
			text,
			...(result?.structuredOutput !== undefined ? { structured: result.structuredOutput } : {}),
			...(result?.error ? { error: result.error } : {}),
			...(result?.timedOut ? { timedOut: true } : {}),
			...(result?.savedOutputPath ? { outputPath: result.savedOutputPath } : {}),
			...(result?.artifactPaths ? { artifactPaths: result.artifactPaths } : {}),
		};
	});
}

export function validateDynamicCollection(schema: JsonSchemaObject | undefined, value: DynamicCollectedResult[]): void {
	if (!schema) return;
	const validation = validateStructuredOutputValue(schema, value);
	if (validation.status === "invalid") {
		throw new DynamicFanoutError(`Collected output validation failed: ${validation.message}`);
	}
}