import { FieldDefinitionNode, NameNode } from "graphql";
import { ITableData, IConfig } from "../interfaces";
import { ICompiledExpression } from "../expressions/ExpressionCompiler";

function filterRelevantExpressions(expressionObject: ICompiledExpression): boolean {
  return expressionObject.isRequiredAsPermissionExpression === true && expressionObject.excludeFromPermissionExpressions !== true;
}

function createExpressionSql(expressionObject: ICompiledExpression): string {
  if (expressionObject.type === "function") {
    return `${expressionObject.sql} AS "${expressionObject.name}"`;
  }
  if (expressionObject.requiresLateral) {
    return `LATERAL (SELECT ${expressionObject.sql} AS "${expressionObject.name}") AS "${expressionObject.name}"`;
  }
  return `(SELECT ${expressionObject.sql} AS "${expressionObject.name}") AS "${expressionObject.name}"`;
}

function getExpressionName(expressionObject: ICompiledExpression): string {
  return `"${expressionObject.name}"`;
}

export function createView(
  table: ITableData,
  config: IConfig,
  name: string,
  fields: string[],
  expressions: ICompiledExpression[],
  disableSecurityBarrier: boolean
): string[] {
  const statements = [];

  statements.push(`DROP VIEW IF EXISTS "${config.schemaName}"."${name}";`);

  let sql = `CREATE OR REPLACE VIEW "${config.schemaName}"."${name}"${disableSecurityBarrier === true ? "" : " WITH (security_barrier)"} AS `;
  // TODO: Dustin: Put _local_table_ into constant for all queries
  sql += `SELECT ${fields.join(", ")} FROM "${table.schemaName}"."${table.tableName}" AS "_local_table_"`;

  if (expressions.length > 0) {
    sql += `, ${expressions.map(createExpressionSql).join(", ")}`;
  }

  // We only want to allow a user to see entities if he can access any field
  const conditionExpressions = expressions.filter(filterRelevantExpressions);

  if (conditionExpressions.length > 0) {
    sql += ` WHERE (FALSE OR ${conditionExpressions.map(getExpressionName).join(" OR ")})`;
  } else {
    // A view without any expression makes no sense
    return null;
  }

  sql += ";";

  statements.push(sql);

  statements.push(`GRANT SELECT ON "${config.schemaName}"."${name}" TO ${config.userName};`);

  return statements;
}

export function createGqlField(name: string, gqlReturnType: string): FieldDefinitionNode {
  return {
    kind: "FieldDefinition",
    name: {
      kind: "Name",
      value: name
    },
    arguments: [],
    type: {
      kind: "NamedType",
      name: {
        kind: "Name",
        value: gqlReturnType
      }
    },
    directives: []
  };
}