import {
  externalCsvConfigurationSchemaVersion,
  type ExternalCsvConfiguration,
  type ExternalCsvDisplayNameSuggestion,
  type ExternalCsvQuantityRule,
} from "./external-csv-contracts.js";

const supportedCategories = new Set([
  "lighting",
  "single_phase",
  "three_phase",
]);

const requiredColumnKeys = [
  "ifcGuid",
  "roomNumber",
  "roomName",
  "familyAndType",
  "selectionMarker",
  "circuitIdentifier",
  "power",
] as const;

export function assertExternalCsvConfiguration(
  value: unknown
): asserts value is ExternalCsvConfiguration {
  if (!isRecord(value)) {
    throw new Error("External CSV configuration must be an object.");
  }
  if (value.schemaVersion !== externalCsvConfigurationSchemaVersion) {
    throw new Error("Unsupported external CSV configuration schema version.");
  }
  if (value.encoding !== "utf-8") {
    throw new Error("External CSV encoding must be utf-8.");
  }
  if (value.delimiter !== ";" && value.delimiter !== "," && value.delimiter !== "\t") {
    throw new Error("External CSV delimiter is unsupported.");
  }
  if (value.decimalSeparator !== "," && value.decimalSeparator !== ".") {
    throw new Error("External CSV decimal separator is unsupported.");
  }
  if (value.powerUnit !== "W" && value.powerUnit !== "kW") {
    throw new Error("External CSV power unit is unsupported.");
  }
  assertPositiveFiniteNumber(value.wattsPerSourceUnit, "wattsPerSourceUnit");

  if (!isRecord(value.columns)) {
    throw new Error("External CSV columns must be an object.");
  }
  const mappedColumns = new Set<string>();
  for (const key of requiredColumnKeys) {
    const columnName = assertTrimmedString(value.columns[key], `columns.${key}`);
    if (mappedColumns.has(columnName)) {
      throw new Error(`External CSV column is mapped more than once: ${columnName}`);
    }
    mappedColumns.add(columnName);
  }
  if (value.columns.quantity !== null) {
    const quantityColumn = assertTrimmedString(
      value.columns.quantity,
      "columns.quantity"
    );
    if (mappedColumns.has(quantityColumn)) {
      throw new Error(`External CSV column is mapped more than once: ${quantityColumn}`);
    }
    mappedColumns.add(quantityColumn);
  }

  if (!Array.isArray(value.additionalSourceMappings)) {
    throw new Error("External CSV additional source mappings must be an array.");
  }
  const targetFields = new Set<string>();
  for (const [index, mapping] of value.additionalSourceMappings.entries()) {
    if (!isRecord(mapping)) {
      throw new Error(`additionalSourceMappings.${index} must be an object.`);
    }
    const sourceColumn = assertTrimmedString(
      mapping.sourceColumn,
      `additionalSourceMappings.${index}.sourceColumn`
    );
    const targetField = assertTrimmedString(
      mapping.targetField,
      `additionalSourceMappings.${index}.targetField`
    );
    if (mappedColumns.has(sourceColumn)) {
      throw new Error(`External CSV column is mapped more than once: ${sourceColumn}`);
    }
    if (targetFields.has(targetField)) {
      throw new Error(`External target field is mapped more than once: ${targetField}`);
    }
    mappedColumns.add(sourceColumn);
    targetFields.add(targetField);
  }

  if (!Array.isArray(value.familyTypeRules)) {
    throw new Error("External CSV family/type rules must be an array.");
  }
  const exactFamilyValues = new Set<string>();
  for (const [index, rule] of value.familyTypeRules.entries()) {
    if (!isRecord(rule)) {
      throw new Error(`familyTypeRules.${index} must be an object.`);
    }
    const exactFamilyAndType = assertTrimmedString(
      rule.exactFamilyAndType,
      `familyTypeRules.${index}.exactFamilyAndType`
    );
    if (exactFamilyValues.has(exactFamilyAndType)) {
      throw new Error(
        `External CSV family/type rule is duplicated: ${exactFamilyAndType}`
      );
    }
    exactFamilyValues.add(exactFamilyAndType);
    assertTrimmedString(
      rule.internalDeviceType,
      `familyTypeRules.${index}.internalDeviceType`
    );
    if (rule.connectionKind !== null) {
      assertTrimmedString(
        rule.connectionKind,
        `familyTypeRules.${index}.connectionKind`
      );
    }
    if (typeof rule.category !== "string" || !supportedCategories.has(rule.category)) {
      throw new Error(`familyTypeRules.${index}.category is unsupported.`);
    }
    assertQuantityRule(rule.quantityRule, index);
    if (rule.quantityRule.kind === "mapped-column" && value.columns.quantity === null) {
      throw new Error(
        `familyTypeRules.${index}.quantityRule requires a configured quantity column.`
      );
    }
    assertDisplayNameSuggestion(rule.displayNameSuggestion, index);
  }
}

export function validateExternalCsvConfiguration(
  value: unknown
): { success: true; data: ExternalCsvConfiguration } | { success: false; error: string } {
  try {
    assertExternalCsvConfiguration(value);
    return { success: true, data: value };
  } catch (error) {
    return {
      success: false,
      error: error instanceof Error ? error.message : "Invalid external CSV configuration.",
    };
  }
}

function assertQuantityRule(value: unknown, index: number): asserts value is ExternalCsvQuantityRule {
  if (!isRecord(value)) {
    throw new Error(`familyTypeRules.${index}.quantityRule must be an object.`);
  }
  if (value.kind === "mapped-column") {
    return;
  }
  if (value.kind === "fixed") {
    assertPositiveFiniteNumber(value.quantity, `familyTypeRules.${index}.quantityRule.quantity`);
    return;
  }
  throw new Error(`familyTypeRules.${index}.quantityRule is unsupported.`);
}

function assertDisplayNameSuggestion(
  value: unknown,
  index: number
): asserts value is ExternalCsvDisplayNameSuggestion | null {
  if (value === null) {
    return;
  }
  if (!isRecord(value)) {
    throw new Error(`familyTypeRules.${index}.displayNameSuggestion must be an object or null.`);
  }
  if (value.kind === "selection-marker" || value.kind === "family-and-type") {
    return;
  }
  if (value.kind === "fixed") {
    assertTrimmedString(value.value, `familyTypeRules.${index}.displayNameSuggestion.value`);
    return;
  }
  throw new Error(`familyTypeRules.${index}.displayNameSuggestion is unsupported.`);
}

function assertPositiveFiniteNumber(value: unknown, field: string) {
  if (typeof value !== "number" || !Number.isFinite(value) || value <= 0) {
    throw new Error(`${field} must be a positive finite number.`);
  }
}

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

function isRecord(value: unknown): value is Record<string, unknown> {
  return value !== null && typeof value === "object" && !Array.isArray(value);
}