import {
  GraphQLBoolean,
  GraphQLString,
  GraphQLInt,
  GraphQLScalarType,
  GraphQLObjectType,
  GraphQLInputObjectType,
  GraphQLList,
  GraphQLNonNull,
  type GraphQLInputType,
  type GraphQLOutputType,
  type GraphQLInputFieldConfigMap,
  type GraphQLFieldConfigMap,
  type GraphQLEnumType,
  type DocumentNode,
  type SelectionSetNode,
  type FragmentDefinitionNode,
} from "graphql";
import { createHash } from "node:crypto";
import {
  valueType,
  type ValueType,
  type InterfaceRevision,
  type InterfaceRevisionId,
  type RelationshipInterfaceMember,
} from "../capability-model/types.js";
import {
  aggregateType,
  aggregateOperators,
  queryKeyType,
  type QueryRow,
  type AggregateOperator,
} from "./relational.js";
import { QueryCompileError } from "./types.js";

export const rowKey = (row: QueryRow): string => JSON.stringify(row);
export const objectRow = (
  interfaceRevisionId: InterfaceRevisionId,
  membership?: { keyType?: "string" | "boolean" | "int64" },
): QueryRow => ({ kind: "object", interfaceRevisionId, ...(membership ? { membership } : {}) });
export type SchemaRowField = { kind: "leaf"; type: ValueType } | { kind: "row"; row: QueryRow; optional: boolean };
export interface RelationalSchemaEnvironment {
  contracts: Map<InterfaceRevisionId, InterfaceRevision>;
  target(member: RelationshipInterfaceMember): InterfaceRevisionId;
  name(id: InterfaceRevisionId): string;
  scalar(type: ValueType): GraphQLInputType & GraphQLOutputType;
  comparison(type: ValueType): GraphQLInputObjectType;
  scalarTypes: Map<string, ValueType>;
  direction: GraphQLEnumType;
  cursor: GraphQLScalarType;
  pageInfo: GraphQLObjectType;
}

export function relationalSchema(env: RelationalSchemaEnvironment, document?: DocumentNode) {
  const outputCache = new Map<string, GraphQLObjectType>();
  const inputCache = new Map<string, GraphQLInputObjectType>();
  const referenceCache = new Map<string, GraphQLScalarType>();
  const rowsets = new Map<string, QueryRow>();
  const expansionPaths = new Map<string, Map<string, string[]>>();
  const roles = new Map<
    string,
    { kind: "rowset" | "aggregate" | "groups" | "keys" | "expand" | "relations"; row: QueryRow }
  >();
  const many = (member: RelationshipInterfaceMember) =>
    member.cardinality === "many" || member.cardinality === "many-unique";
  const relationRow = (member: RelationshipInterfaceMember) =>
    objectRow(env.target(member), { keyType: member.keyType });
  const relations = (row: QueryRow) =>
    row.kind === "object"
      ? env.contracts
          .get(row.interfaceRevisionId)!
          .members.filter(
            (member): member is RelationshipInterfaceMember => member.kind === "relationship" && !!member.queryRead,
          )
      : [];
  const fields = (row: QueryRow): Map<string, SchemaRowField> => {
    if (row.kind === "pair")
      return new Map([
        ["source", { kind: "row", row: row.source, optional: false }],
        ["target", { kind: "row", row: row.target, optional: false }],
      ]);
    return new Map(
      env.contracts.get(row.interfaceRevisionId)!.members.flatMap((member): [string, SchemaRowField][] => {
        if (member.kind === "operation" || !member.queryRead) return [];
        if (member.kind === "value") return [[member.displayName, { kind: "leaf", type: member.valueType }]];
        if (many(member)) return [];
        return [
          [
            member.displayName,
            { kind: "row", row: objectRow(env.target(member)), optional: member.cardinality === "optional-one" },
          ],
        ];
      }),
    );
  };
  const refs = (id: InterfaceRevisionId) => {
    let result = referenceCache.get(id);
    if (!result) {
      result = new GraphQLScalarType({
        name: `QxRef_${env.name(id)}`,
        parseValue: (value) => value,
        parseLiteral() {
          throw new Error("Managed references must be supplied as typed variables");
        },
      });
      referenceCache.set(id, result);
      env.scalarTypes.set(result.name, valueType.interfaceRef(id));
    }
    return result;
  };
  const scalar = (type: ValueType): GraphQLInputType & GraphQLOutputType => {
    if (type.kind === "optional") return scalar(type.value);
    return type.kind === "object-ref" && type.expectation.kind === "interface"
      ? refs(type.expectation.interfaceRevisionId)
      : env.scalar(type);
  };
  const leafFields = (row: QueryRow) => {
    const result = new Map<string, ValueType>();
    if (row.kind === "object") result.set("ref", valueType.interfaceRef(row.interfaceRevisionId));
    if (row.kind === "pair" || row.membership) result.set("entry", valueType.string);
    if (row.kind === "object" && row.membership?.keyType)
      result.set(
        "mapKey",
        row.membership.keyType === "boolean"
          ? valueType.bool
          : row.membership.keyType === "int64"
            ? valueType.int64
            : valueType.string,
      );
    return result;
  };
  const typeName = (role: string, row: QueryRow, suffix = "") =>
    `Qx${role}_${createHash("sha256")
      .update(rowKey(row) + suffix)
      .digest("hex")
      .slice(0, 16)}`;
  const out = (role: string, row: QueryRow, make: () => GraphQLFieldConfigMap<unknown, unknown>, suffix = "") => {
    const key = typeName(role, row, suffix);
    let result = outputCache.get(key);
    if (!result) {
      result = new GraphQLObjectType({ name: key, fields: make });
      outputCache.set(key, result);
    }
    return result;
  };
  const inp = (role: string, row: QueryRow, make: () => GraphQLInputFieldConfigMap, suffix = "") => {
    const key = typeName(role, row, suffix);
    let result = inputCache.get(key);
    if (!result) {
      result = new GraphQLInputObjectType({ name: key, fields: make });
      inputCache.set(key, result);
    }
    return result;
  };
  const compare = (type: ValueType) => {
    const base = type.kind === "optional" ? type.value : type;
    if (base.kind !== "object-ref") return env.comparison(type);
    return inp(
      "RefCompare",
      objectRow(
        base.expectation.kind === "interface"
          ? base.expectation.interfaceRevisionId
          : (() => {
              throw new Error("Expected interface reference");
            })(),
      ),
      () => ({ eq: { type: scalar(type) }, in: { type: new GraphQLList(new GraphQLNonNull(scalar(type))) } }),
    );
  };
  // Recursive interface graphs are interned. Synthetic pair graphs are finite and document-driven.
  const columns = (
    row: QueryRow,
    operator?: Exclude<AggregateOperator, "count">,
    nullable = false,
  ): GraphQLObjectType =>
    out(
      "Columns",
      row,
      () => {
        const result: GraphQLFieldConfigMap<unknown, unknown> = {};
        for (const [name, field] of fields(row)) {
          if (field.kind === "row")
            result[name] = { type: new GraphQLNonNull(columns(field.row, operator, nullable || field.optional)) };
          else {
            let type = field.type;
            if (operator) {
              try {
                type = aggregateType(operator, type);
              } catch {
                continue;
              }
            } else if (!queryKeyType(type)) continue;
            result[name] = {
              type:
                type.kind === "optional" || (!operator && nullable) ? scalar(type) : new GraphQLNonNull(scalar(type)),
            };
          }
        }
        const metadata: GraphQLFieldConfigMap<unknown, unknown> = {};
        for (const [name, type] of leafFields(row)) {
          if (operator && operator !== "countPresent") continue;
          const t = scalar(operator ? aggregateType(operator, type) : type);
          metadata[name] = { type: !operator && nullable ? t : new GraphQLNonNull(t) };
        }
        if (Object.keys(metadata).length)
          result._qx = { type: new GraphQLNonNull(out("ColumnsMeta", row, () => metadata, `${operator}:${nullable}`)) };
        // A type may have no matching scalar at this node; a private schema sentinel
        // keeps it valid while compiler validation forbids selecting that sentinel.
        if (!Object.keys(result).length) result._unavailable = { type: GraphQLBoolean };
        return result;
      },
      `${operator}:${nullable}`,
    );
  const aggregate = (row: QueryRow): GraphQLObjectType => {
    const result = out("Aggregate", row, () =>
      Object.fromEntries(
        aggregateOperators.map((op) => [
          op,
          { type: new GraphQLNonNull(op === "count" ? env.scalar(valueType.uint64) : columns(row, op)) },
        ]),
      ),
    );
    roles.set(result.name, { kind: "aggregate", row });
    return result;
  };
  const keys = (row: QueryRow): GraphQLInputObjectType =>
    inp("Keys", row, () => {
      const result: GraphQLInputFieldConfigMap = {};
      for (const [name, field] of fields(row)) {
        if (field.kind === "row") result[name] = { type: keys(field.row) };
        else if (queryKeyType(field.type)) result[name] = { type: GraphQLBoolean };
      }
      const meta = Object.fromEntries([...leafFields(row)].map(([name]) => [name, { type: GraphQLBoolean }]));
      if (Object.keys(meta).length) result._qx = { type: inp("KeyMeta", row, () => meta) };
      return result;
    });
  const comparisons = (
    row: QueryRow,
    operator?: Exclude<AggregateOperator, "count">,
    ordering = false,
  ): GraphQLInputObjectType =>
    inp(
      "Expressions",
      row,
      () => {
        const result: GraphQLInputFieldConfigMap = {};
        for (const [name, field] of fields(row)) {
          if (field.kind === "row") result[name] = { type: comparisons(field.row, operator, ordering) };
          else {
            let type = field.type;
            if (operator) {
              try {
                type = aggregateType(operator, type);
              } catch {
                continue;
              }
            }
            result[name] = { type: ordering ? env.direction : compare(type) };
          }
        }
        const meta: GraphQLInputFieldConfigMap = {};
        for (const [name, type] of leafFields(row))
          if (!operator || operator === "countPresent")
            meta[name] = { type: ordering ? env.direction : compare(operator ? aggregateType(operator, type) : type) };
        if (Object.keys(meta).length)
          result._qx = { type: inp("ExpressionMeta", row, () => meta, `${operator}:${ordering}`) };
        if (!Object.keys(result).length) result._unavailable = { type: GraphQLBoolean };
        return result;
      },
      `${operator}:${ordering}`,
    );
  const having = (row: QueryRow, ordering = false): GraphQLInputObjectType =>
    inp(
      "Having",
      row,
      () => {
        const result: GraphQLInputFieldConfigMap = { group: { type: comparisons(row, undefined, ordering) } };
        for (const op of aggregateOperators)
          result[op] = {
            type:
              op === "count" ? (ordering ? env.direction : compare(valueType.uint64)) : comparisons(row, op, ordering),
          };
        if (!ordering)
          Object.assign(result, {
            and: { type: new GraphQLList(new GraphQLNonNull(having(row))) },
            or: { type: new GraphQLList(new GraphQLNonNull(having(row))) },
            not: { type: having(row) },
          });
        return result;
      },
      String(ordering),
    );
  const where = (row: QueryRow): GraphQLInputObjectType =>
    inp("Where", row, () => {
      const result: GraphQLInputFieldConfigMap = {
        and: { type: new GraphQLList(new GraphQLNonNull(where(row))) },
        or: { type: new GraphQLList(new GraphQLNonNull(where(row))) },
        not: { type: where(row) },
      };
      for (const [name, field] of fields(row)) {
        if (row.kind === "object" && field.kind === "row") continue;
        if (name in result) throw new QueryCompileError("QUERY_SCHEMA_NAME", `Reserved predicate name ${name}`);
        result[name] = { type: field.kind === "row" ? where(field.row) : compare(field.type) };
      }
      result._qx = {
        type: inp("WhereMeta", row, () => {
          const meta: GraphQLInputFieldConfigMap = {};
          for (const [name, type] of leafFields(row)) meta[name] = { type: compare(type) };
          const edges = relations(row);
          if (edges.length)
            meta.relations = {
              type: inp("WhereRelations", row, () =>
                Object.fromEntries(
                  edges.map((member) => {
                    const target = relationRow(member);
                    return [
                      member.displayName,
                      {
                        type: inp(
                          "RelationPredicate",
                          target,
                          (): GraphQLInputFieldConfigMap =>
                            many(member)
                              ? {
                                  some: { type: where(target) },
                                  none: { type: where(target) },
                                  aggregate: {
                                    type: inp("ReductionPredicate", target, () => ({
                                      where: { type: where(target) },
                                      having: { type: new GraphQLNonNull(having(target)) },
                                    })),
                                  },
                                }
                              : { is: { type: where(target) }, isNull: { type: GraphQLBoolean } },
                          rowKey(row) + member.id,
                        ),
                      },
                    ];
                  }),
                ),
              ),
            };
          return meta;
        }),
      };
      return result;
    });

  const fragments = new Map(
    (document?.definitions ?? [])
      .filter((d): d is FragmentDefinitionNode => d.kind === "FragmentDefinition")
      .map((d) => [d.name.value, d]),
  );
  let visited = 0;
  const selections = (set: SelectionSetNode, active: ReadonlySet<string> = new Set()): import("graphql").FieldNode[] =>
    set.selections.flatMap((node) => {
      if (++visited > 10000)
        throw new QueryCompileError("QUERY_WORK_LIMIT", "Query schema discovery exceeds 10000 nodes");
      if (node.kind === "Field") return [node];
      if (node.kind === "FragmentSpread") {
        if (active.has(node.name.value) || active.size >= 128)
          throw new QueryCompileError("QUERY_VALIDATION", "Cyclic or excessively nested fragments");
        const fragment = fragments.get(node.name.value);
        return fragment ? selections(fragment.selectionSet, new Set([...active, node.name.value])) : [];
      }
      return [];
    });
  const discoverExpansion = (root: QueryRow, current: QueryRow, set: SelectionSetNode, path: string[] = []) => {
    for (const node of selections(set)) {
      if (!node.selectionSet) continue;
      const member = relations(current).find((m) => m.displayName === node.name.value);
      const next = [...path, node.name.value];
      if (member && many(member)) {
        const map = expansionPaths.get(rowKey(root)) ?? new Map();
        map.set(next.join("."), next);
        expansionPaths.set(rowKey(root), map);
        discoverRows({ kind: "pair", source: root, target: relationRow(member) }, node.selectionSet);
      } else {
        const field = fields(current).get(node.name.value);
        if (field?.kind === "row") discoverExpansion(root, field.row, node.selectionSet, next);
      }
    }
  };
  const discoverRows = (row: QueryRow, set: SelectionSetNode) => {
    rowsets.set(rowKey(row), row);
    if (rowsets.size > 256) throw new QueryCompileError("QUERY_WORK_LIMIT", "Query exceeds 256 row shapes");
    for (const node of selections(set))
      if (node.selectionSet) {
        if (node.name.value === "expand") discoverExpansion(row, row, node.selectionSet);
        else if (node.name.value === "filter" || node.name.value === "distinct") discoverRows(row, node.selectionSet);
      }
  };
  const discoverObject = (row: QueryRow, set: SelectionSetNode) => {
    for (const node of selections(set))
      if (node.selectionSet) {
        if (node.name.value === "_qx") {
          for (const meta of selections(node.selectionSet))
            if (meta.name.value === "relations" && meta.selectionSet)
              for (const edge of selections(meta.selectionSet)) {
                const member = relations(row).find((m) => m.displayName === edge.name.value);
                if (member && many(member) && edge.selectionSet) discoverRows(relationRow(member), edge.selectionSet);
              }
        } else {
          const member = relations(row).find((m) => m.displayName === node.name.value);
          if (member) {
            if (!many(member)) discoverObject(objectRow(env.target(member)), node.selectionSet);
            else
              for (const entries of selections(node.selectionSet))
                if (entries.name.value === "entries" && entries.selectionSet)
                  for (const child of selections(entries.selectionSet))
                    if (child.name.value === "node" && child.selectionSet)
                      discoverObject(objectRow(env.target(member)), child.selectionSet);
          }
        }
      }
  };
  const discover = (root: InterfaceRevisionId) => {
    for (const operation of document?.definitions ?? [])
      if (operation.kind === "OperationDefinition")
        for (const node of selections(operation.selectionSet))
          if (node.name.value === "root" && node.selectionSet) discoverObject(objectRow(root), node.selectionSet);
  };
  const expand = (root: QueryRow, current: QueryRow, path: string[] = []): GraphQLObjectType =>
    out(
      "Expand",
      current,
      () => {
        const result: GraphQLFieldConfigMap<unknown, unknown> = {};
        const paths = [...(expansionPaths.get(rowKey(root))?.values() ?? [])].filter((p) =>
          path.every((part, i) => p[i] === part),
        );
        for (const name of new Set(paths.map((p) => p[path.length]).filter((v): v is string => !!v))) {
          const member = relations(current).find((m) => m.displayName === name);
          if (member && many(member))
            result[name] = {
              type: new GraphQLNonNull(rowset({ kind: "pair", source: root, target: relationRow(member) })),
            };
          else {
            const field = fields(current).get(name);
            if (field?.kind === "row")
              result[name] = { type: new GraphQLNonNull(expand(root, field.row, [...path, name])) };
          }
        }
        if (!Object.keys(result).length) result._unavailable = { type: GraphQLBoolean };
        return result;
      },
      rowKey(root) + JSON.stringify(path),
    );
  const rowset = (row: QueryRow): GraphQLObjectType => {
    const result = out("Rows", row, () => {
      const entry = out("GroupEntry", row, () => ({
        key: { type: new GraphQLNonNull(GraphQLString) },
        cursor: { type: env.cursor },
        group: { type: new GraphQLNonNull(columns(row)) },
        aggregate: { type: new GraphQLNonNull(aggregate(row)) },
      }));
      const connection = out("Groups", row, () => ({
        entries: { type: new GraphQLNonNull(new GraphQLList(new GraphQLNonNull(entry))) },
        pageInfo: { type: new GraphQLNonNull(env.pageInfo) },
      }));
      roles.set(connection.name, { kind: "groups", row });
      return {
        filter: { type: new GraphQLNonNull(rowset(row)), args: { where: { type: new GraphQLNonNull(where(row)) } } },
        distinct: { type: new GraphQLNonNull(rowset(row)), args: { by: { type: new GraphQLNonNull(keys(row)) } } },
        expand: { type: new GraphQLNonNull(expand(row, row)) },
        aggregate: { type: new GraphQLNonNull(aggregate(row)), args: { where: { type: where(row) } } },
        groups: {
          type: new GraphQLNonNull(connection),
          args: {
            by: { type: new GraphQLNonNull(keys(row)) },
            where: { type: where(row) },
            having: { type: having(row) },
            orderBy: { type: new GraphQLList(new GraphQLNonNull(having(row, true))) },
            first: { type: GraphQLInt },
            all: { type: GraphQLInt },
            after: { type: env.cursor },
          },
        },
      };
    });
    roles.set(result.name, { kind: "rowset", row });
    return result;
  };
  const helpers = (id: InterfaceRevisionId): GraphQLObjectType | undefined => {
    const row = objectRow(id),
      edges = relations(row).filter(many);
    if (!edges.length) return undefined;
    const result = out("Relations", row, () =>
      Object.fromEntries(
        edges.map((member) => [member.displayName, { type: new GraphQLNonNull(rowset(relationRow(member))) }]),
      ),
    );
    roles.set(result.name, { kind: "relations", row });
    return result;
  };
  return { refs, fields, relations, relationRow, where, rowset, helpers, roles, discover, scalar, compare };
}