import { SUPPORTED_BUCKET_SCHEMA_VERSION } from './types';
import type { LocalizedString } from '$lib/types/i18n';
import type {
	BucketDrilldownMetric,
	BucketGroupedBars,
	BucketGroupedBarsModel,
	BucketHeatmap,
	BucketLatencyMs,
	BucketMetricMap,
	BucketPareto,
	BucketParetoModel,
	BucketPerformance,
	BucketPerformanceRow,
	BucketRadar,
	BucketRobustness,
	BucketRobustnessRow,
	BucketScatter,
	BucketScatterPoint,
	BucketScatterRowId,
	BucketSchemaVersion,
	BucketVisualizationBase,
	BucketVisualizationWithSubtitle
} from './types';

function record(value: unknown, field: string): Record<string, unknown> {
	if (typeof value !== 'object' || value === null || Array.isArray(value)) {
		throw new Error(`Field "${field}" must be an object.`);
	}
	return value as Record<string, unknown>;
}

function array(value: unknown, field: string): unknown[] {
	if (!Array.isArray(value)) throw new Error(`Field "${field}" must be an array.`);
	return value;
}

function string(value: unknown, field: string) {
	if (typeof value !== 'string' || value.trim() === '') {
		throw new Error(`Field "${field}" must be a non-empty string.`);
	}
	return value;
}

function nullableString(value: unknown, field: string) {
	return value === null ? null : string(value, field);
}

function stringArray(value: unknown, field: string) {
	return array(value, field).map((item, index) => string(item, `${field}[${index}]`));
}

function finiteNumber(value: unknown, field: string) {
	if (typeof value !== 'number' || !Number.isFinite(value)) {
		throw new Error(`Field "${field}" must be a finite number.`);
	}
	return value;
}

function nullableNumber(value: unknown, field: string) {
	return value === null ? null : finiteNumber(value, field);
}

function positiveInteger(value: unknown, field: string) {
	const parsed = finiteNumber(value, field);
	if (!Number.isInteger(parsed) || parsed < 1) {
		throw new Error(`Field "${field}" must be a positive integer.`);
	}
	return parsed;
}

function localized(value: unknown, field: string): LocalizedString {
	const item = record(value, field);
	return { en: string(item.en, `${field}.en`), ru: string(item.ru, `${field}.ru`) };
}

function optionalLocalized(value: unknown, field: string) {
	return value === undefined ? undefined : localized(value, field);
}

function schema(value: unknown, field: string): BucketSchemaVersion {
	const version = string(value, field);
	if (version !== SUPPORTED_BUCKET_SCHEMA_VERSION) {
		throw new Error(
			`Unsupported schema "${version}" in ${field}; expected "${SUPPORTED_BUCKET_SCHEMA_VERSION}".`
		);
	}
	return version as BucketSchemaVersion;
}

function base(value: unknown, field: string): BucketVisualizationBase {
	const item = record(value, field);
	return {
		schema_version: schema(item.schema_version, `${field}.schema_version`),
		title: localized(item.title, `${field}.title`)
	};
}

function baseWithSubtitle(value: unknown, field: string): BucketVisualizationWithSubtitle {
	const item = record(value, field);
	return {
		...base(item, field),
		subtitle: optionalLocalized(item.subtitle, `${field}.subtitle`)
	};
}

function metricMap(value: unknown, field: string): BucketMetricMap {
	return Object.fromEntries(
		Object.entries(record(value, field)).map(([rowId, row]) => [
			rowId,
			Object.fromEntries(
				Object.entries(record(row, `${field}.${rowId}`)).map(([modelId, metric]) => [
					modelId,
					nullableNumber(metric, `${field}.${rowId}.${modelId}`)
				])
			)
		])
	);
}

function latency(value: unknown, field: string): BucketLatencyMs {
	const item = record(value, field);
	return {
		p50: nullableNumber(item.p50, `${field}.p50`),
		p95: nullableNumber(item.p95, `${field}.p95`),
		p99: nullableNumber(item.p99, `${field}.p99`)
	};
}

function drilldownMetric(value: unknown, field: string): BucketDrilldownMetric {
	const metric = string(value, field);
	if (metric !== 'score' && metric !== 'f1' && metric !== 'fpr' && metric !== 'fnr') {
		throw new Error(`Field "${field}" has an unsupported metric.`);
	}
	return metric;
}

function scatterRowId(value: unknown, field: string): BucketScatterRowId {
	const rowId = string(value, field);
	if (rowId !== 'fpr' && rowId !== 'fnr' && rowId !== 'overall') {
		throw new Error(`Field "${field}" has an unsupported row id.`);
	}
	return rowId;
}

function parseScatterValues(
	value: unknown,
	rowIds: readonly BucketScatterRowId[],
	field: string
): Record<BucketScatterRowId, Record<string, number | null>> {
	const item = record(value, field);
	const values: Partial<Record<BucketScatterRowId, Record<string, number | null>>> = {};

	for (const rowId of rowIds) {
		values[rowId] = Object.fromEntries(
			Object.entries(record(item[rowId], `${field}.${rowId}`)).map(([modelId, metric]) => [
				modelId,
				nullableNumber(metric, `${field}.${rowId}.${modelId}`)
			])
		);
	}

	return values as Record<BucketScatterRowId, Record<string, number | null>>;
}

function parseScatterPoint(value: unknown, index: number): BucketScatterPoint {
	const field = `scatter.points[${index}]`;
	const item = record(value, field);
	return {
		model_id: string(item.model_id, `${field}.model_id`),
		fpr: nullableNumber(item.fpr, `${field}.fpr`),
		fnr: nullableNumber(item.fnr, `${field}.fnr`),
		tooltip: nullableString(item.tooltip, `${field}.tooltip`)
	};
}

function parseGroupedBarsModel(value: unknown, index: number): BucketGroupedBarsModel {
	const field = `grouped_bars.models[${index}]`;
	const item = record(value, field);
	return {
		model_id: string(item.model_id, `${field}.model_id`),
		groups: Object.fromEntries(
			Object.entries(record(item.groups, `${field}.groups`)).map(([groupId, groupMetrics]) => {
				const metrics = record(groupMetrics, `${field}.groups.${groupId}`);
				return [
					groupId,
					{
						recall: nullableNumber(metrics.recall, `${field}.groups.${groupId}.recall`),
						precision: nullableNumber(metrics.precision, `${field}.groups.${groupId}.precision`),
						f1: nullableNumber(metrics.f1, `${field}.groups.${groupId}.f1`)
					}
				];
			})
		)
	};
}

function parseParetoModel(value: unknown, modelId: string): BucketParetoModel {
	const field = `pareto.by_model_id.${modelId}`;
	const item = record(value, field);
	return {
		latency_ms: latency(item.latency_ms, `${field}.latency_ms`),
		integral: nullableNumber(item.integral, `${field}.integral`),
		fpr: nullableNumber(item.fpr, `${field}.fpr`)
	};
}

function parsePerformanceRow(value: unknown, index: number): BucketPerformanceRow {
	const field = `performance.rows[${index}]`;
	const item = record(value, field);
	return {
		model_id: string(item.model_id, `${field}.model_id`),
		rank: positiveInteger(item.rank, `${field}.rank`),
		latency_ms: latency(item.latency_ms, `${field}.latency_ms`),
		error_rate: nullableNumber(item.error_rate ?? null, `${field}.error_rate`),
		integral: nullableNumber(item.integral, `${field}.integral`)
	};
}

function parseRobustnessRow(value: unknown, index: number): BucketRobustnessRow {
	const field = `robustness.rows[${index}]`;
	const item = record(value, field);
	return {
		model_id: string(item.model_id, `${field}.model_id`),
		score_real: nullableNumber(item.score_real, `${field}.score_real`),
		score_robust: nullableNumber(item.score_robust, `${field}.score_robust`),
		delta_score: nullableNumber(item.delta_score, `${field}.delta_score`),
		fnr_real: nullableNumber(item.fnr_real, `${field}.fnr_real`),
		fnr_robust: nullableNumber(item.fnr_robust, `${field}.fnr_robust`),
		delta_fnr: nullableNumber(item.delta_fnr, `${field}.delta_fnr`),
		fpr_real: nullableNumber(item.fpr_real ?? null, `${field}.fpr_real`),
		fpr_robust: nullableNumber(item.fpr_robust ?? null, `${field}.fpr_robust`),
		delta_fpr: nullableNumber(item.delta_fpr ?? null, `${field}.delta_fpr`),
		category_label: localized(item.category_label, `${field}.category_label`)
	};
}

export function parseBucketRadar(value: unknown): BucketRadar {
	const item = record(value, 'radar');
	return {
		...baseWithSubtitle(item, 'radar'),
		model_ids: stringArray(item.model_ids, 'radar.model_ids'),
		group_ids: stringArray(item.group_ids, 'radar.group_ids'),
		default_model_ids: stringArray(item.default_model_ids, 'radar.default_model_ids'),
		values: metricMap(item.values, 'radar.values'),
		f1_values: metricMap(item.f1_values, 'radar.f1_values')
	};
}

export function parseBucketScatter(value: unknown): BucketScatter {
	const item = record(value, 'scatter');
	const rowIds = array(item.row_ids, 'scatter.row_ids').map((rowId, index) =>
		scatterRowId(rowId, `scatter.row_ids[${index}]`)
	);
	return {
		...base(item, 'scatter'),
		x_axis: localized(item.x_axis, 'scatter.x_axis'),
		y_axis: localized(item.y_axis, 'scatter.y_axis'),
		points: array(item.points, 'scatter.points').map(parseScatterPoint),
		row_ids: rowIds,
		values: parseScatterValues(item.values, rowIds, 'scatter.values')
	};
}

export function parseBucketHeatmap(value: unknown): BucketHeatmap {
	const item = record(value, 'heatmap');
	return {
		...baseWithSubtitle(item, 'heatmap'),
		metric: drilldownMetric(item.metric, 'heatmap.metric'),
		row_ids: stringArray(item.row_ids, 'heatmap.row_ids'),
		column_ids: stringArray(item.column_ids, 'heatmap.column_ids'),
		values: metricMap(item.values, 'heatmap.values')
	};
}

export function parseBucketGroupedBars(value: unknown): BucketGroupedBars {
	const item = record(value, 'grouped_bars');
	return {
		...baseWithSubtitle(item, 'grouped_bars'),
		group_ids: stringArray(item.group_ids, 'grouped_bars.group_ids'),
		models: array(item.models, 'grouped_bars.models').map(parseGroupedBarsModel)
	};
}

export function parseBucketPareto(value: unknown): BucketPareto {
	const item = record(value, 'pareto');
	return {
		...baseWithSubtitle(item, 'pareto'),
		x_axis: localized(item.x_axis, 'pareto.x_axis'),
		y_axis: localized(item.y_axis, 'pareto.y_axis'),
		by_model_id: Object.fromEntries(
			Object.entries(record(item.by_model_id, 'pareto.by_model_id')).map(([modelId, model]) => [
				modelId,
				parseParetoModel(model, modelId)
			])
		)
	};
}

export function parseBucketPerformance(value: unknown): BucketPerformance {
	const item = record(value, 'performance');
	return {
		...base(item, 'performance'),
		rows: array(item.rows, 'performance.rows').map(parsePerformanceRow)
	};
}

export function parseBucketRobustness(value: unknown): BucketRobustness {
	const item = record(value, 'robustness');
	return {
		...base(item, 'robustness'),
		rows: array(item.rows, 'robustness.rows').map(parseRobustnessRow)
	};
}