import { z } from 'zod';
import type { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';
import type { CallToolResult } from '@modelcontextprotocol/sdk/types.js';
import type { SoapClient } from '../clients/soap-client.js';
import { formatToolError, classifyError, getErrorHint } from '../utils/errors.js';

interface FieldDefinition {
  name: string;
  type: string;
  length: string;
  label: string;
}

// @_ prefix: fast-xml-parser attributeNamePrefix config in soap-client.ts
function parseFieldDefinitions(data: unknown): FieldDefinition[] {
  if (!data || typeof data !== 'object') return [];

  const fields: FieldDefinition[] = [];
  const fldArray = extractFldArray(data);

  for (const fld of fldArray) {
    if (!fld || typeof fld !== 'object') continue;
    const f = fld as Record<string, unknown>;
    fields.push({
      name: String(f['@_NAM'] ?? f['NAM'] ?? ''),
      type: String(f['@_TYP'] ?? f['TYP'] ?? ''),
      length: String(f['@_LEN'] ?? f['LEN'] ?? ''),
      label: String(f['@_C_ENG'] ?? f['C_ENG'] ?? ''),
    });
  }

  return fields.filter((f) => f.name !== '');
}

function extractFldArray(data: unknown): unknown[] {
  if (!data || typeof data !== 'object') return [];
  const obj = data as Record<string, unknown>;

  if (Array.isArray(obj['FLD'])) return obj['FLD'];
  if (obj['FLD'] && typeof obj['FLD'] === 'object') return [obj['FLD']];

  for (const key of Object.keys(obj)) {
    const child = obj[key];
    if (child && typeof child === 'object' && !Array.isArray(child)) {
      const childObj = child as Record<string, unknown>;
      if (Array.isArray(childObj['FLD'])) return childObj['FLD'];
      if (childObj['FLD'] && typeof childObj['FLD'] === 'object') return [childObj['FLD']];
    }
  }

  return [];
}

export function registerDescribeEntityTool(
  server: McpServer,
  soapClient: SoapClient,
): void {
  server.registerTool(
    'sage_describe_entity',
    {
      description:
        'Get field definitions for a Sage X3 SOAP object. Returns field names, types, lengths, and English labels. Essential for understanding X3 field codes.',
      inputSchema: {
        publicName: z
          .string()
          .describe('SOAP publication name, e.g. SIH, SOH, WSBPC, WITM'),
      },
      annotations: {
        readOnlyHint: true,
        destructiveHint: false,
        idempotentHint: true,
        openWorldHint: false,
      },
    },
    async ({ publicName }): Promise<CallToolResult> => {
      try {
        const result = await soapClient.getDescription(publicName);

        if (result.status === 1) {
          const fields = parseFieldDefinitions(result.data);
          return {
            content: [
              {
                type: 'text' as const,
                text: JSON.stringify({ publicName, fields, fieldCount: fields.length }),
              },
            ],
          };
        }

        const messages = result.messages.map((m) => m.message).join('; ');
        return formatToolError(
          new Error(messages || 'Failed to get entity description'),
          'Check the publicName. Common SOAP publications: SIH (invoices), SOH (sales orders), WSBPC (customers), WITM (items).',
        );
      } catch (error) {
        const classification = classifyError(error);
        return formatToolError(error, getErrorHint(classification));
      }
    },
  );
}