import {
  type FieldValue,
  isStruct,
  type PropertyBag,
  type PropertyValue,
  type StructValue,
  withFieldRenamed,
  withoutField,
} from '../model/Properties';
import {
  type BehaviorAsset,
  isKeptVariable,
  isPrivateVariable,
  setKeptVariable,
  setPrivateVariable,
  type VariableOwnerAsset,
} from '../model/Asset';
import { overrideSites } from '../model/instance';
import type { Project } from '../model/Project';
import type { VariableKind } from '../properties/kinds';
import {
  emptyFieldValue,
  isValidFieldName,
  isValidVariableName,
  type PropertyDef,
  type StructFieldDef,
  variableDef,
} from '../properties/PropertySchema';
import { valueAt, withValueAt } from '../properties/valuePath';
import { moveItem, type Removed, removeFirst, restoreAt } from '../util/list';
import { type Command, CommandError, MoveCommand, RenameCommand } from './Command';
import { renameVariablePorts } from './portCommands';
import { requireBehavior, requireVariableOwner } from './require';

/**
 * The variable's default value is written to `props` as well. On a behavior a new variable starts
 * at its default every call; "Keep" is switched on by hand (#229).
 */
export class AddVariableCommand implements Command {
  readonly label: string;
  readonly def: PropertyDef;

  constructor(
    private readonly assetId: string,
    key: string,
    kind: VariableKind,
  ) {
    this.def = variableDef(key, kind);
    this.label = `Add variable ${key}`;
  }

  execute(project: Project): void {
    const asset = requireVariableOwner(project, this.assetId);
    if (!isValidName(asset, this.def.key)) throw new CommandError(INVALID_NAME);
    if (asset.variables.some((v) => v.key === this.def.key))
      throw new CommandError(`Variable "${this.def.key}" already exists`);
    asset.variables.push(this.def);
    asset.props[this.def.key] = this.def.default;
  }

  undo(project: Project): void {
    const asset = requireVariableOwner(project, this.assetId);
    asset.variables = asset.variables.filter((v) => v.key !== this.def.key);
    delete asset.props[this.def.key];
  }
}

/** One placed object's own value for a variable, remembered so that undo can put it back. */
interface TakenOverride {
  holderId: string;
  objectId: string;
  path: string;
  value: PropertyValue;
}

function takeOverrides(project: Project, assetId: string, key: string): TakenOverride[] {
  const taken: TakenOverride[] = [];
  for (const site of overrideSites(project, (id) => id === assetId)) {
    const value = site.bag[key];
    if (value === undefined) continue;
    taken.push({ holderId: site.holder.id, objectId: site.object.id, path: site.path, value });
    delete site.bag[key];
  }
  return taken;
}

function restoreOverrides(
  project: Project,
  assetId: string,
  key: string,
  taken: readonly TakenOverride[],
): void {
  const sites = overrideSites(project, (id) => id === assetId);
  for (const o of taken) {
    const site = sites.find(
      (s) => s.holder.id === o.holderId && s.object.id === o.objectId && s.path === o.path,
    );
    if (site) site.bag[key] = o.value;
  }
}

/** Removes a variable together with its default and every instance override. */
export class RemoveVariableCommand implements Command {
  readonly label: string;
  private removed?: {
    def: Removed<PropertyDef>;
    value: PropertyValue | undefined;
    kept: boolean;
    hidden: boolean;
  };
  private overrides: TakenOverride[] = [];

  constructor(
    private readonly assetId: string,
    private readonly key: string,
  ) {
    this.label = `Remove variable ${key}`;
  }

  execute(project: Project): void {
    const asset = requireVariableOwner(project, this.assetId);
    const def = removeFirst(asset.variables, (v) => v.key === this.key);
    if (!def) throw new CommandError(`Variable "${this.key}" not found`);
    const kept = asset.type === 'behavior' && isKeptVariable(asset, this.key);
    const hidden = isPrivateVariable(asset, this.key);
    this.removed = { def, value: asset.props[this.key], kept, hidden };
    delete asset.props[this.key];
    if (asset.type === 'behavior') {
      setKeptVariable(asset, this.key, false);
      setPrivateVariable(asset, this.key, false);
    }
    this.overrides = takeOverrides(project, this.assetId, this.key);
  }

  undo(project: Project): void {
    if (!this.removed) return;
    const asset = requireVariableOwner(project, this.assetId);
    restoreAt(asset.variables, [this.removed.def]);
    if (this.removed.value !== undefined) asset.props[this.key] = this.removed.value;
    if (asset.type === 'behavior') {
      if (this.removed.kept) setKeptVariable(asset, this.key, true);
      if (this.removed.hidden) setPrivateVariable(asset, this.key, true);
    }
    restoreOverrides(project, this.assetId, this.key, this.overrides);
  }
}

/** Renames everywhere: definition, default, instance overrides and the graph nodes referring to it. */
export class RenameVariableCommand extends RenameCommand {
  constructor(
    private readonly assetId: string,
    from: string,
    to: string,
  ) {
    super(`Rename variable ${from}`, from, to);
  }

  protected rename(project: Project, from: string, to: string): void {
    const asset = requireVariableOwner(project, this.assetId);
    if (from === to) return;
    if (!isValidName(asset, to)) throw new CommandError(INVALID_NAME);
    const def = asset.variables.find((v) => v.key === from);
    if (!def) throw new CommandError(`Variable "${from}" not found`);
    if (asset.variables.some((v) => v.key === to)) throw new CommandError(`Variable "${to}" already exists`);
    def.key = to;
    def.label = to;
    // Renamed in place, so the switches keep their spot in the list.
    if (asset.type === 'behavior') {
      if (asset.keptVariables) asset.keptVariables = asset.keptVariables.map((k) => (k === from ? to : k));
      if (asset.privateVariables)
        asset.privateVariables = asset.privateVariables.map((k) => (k === from ? to : k));
    }
    if (asset.props[from] !== undefined) {
      asset.props[to] = asset.props[from]!;
      delete asset.props[from];
    }
    for (const { bag } of overrideSites(project, (id) => id === this.assetId)) {
      if (bag[from] === undefined) continue;
      bag[to] = bag[from]!;
      delete bag[from];
    }
    renameVariablePorts(project, this.assetId, from, to);
  }
}

/** Only the order changes: values and the ports naming a variable go by its name (#310). */
export class MoveVariableCommand extends MoveCommand {
  constructor(
    private readonly assetId: string,
    from: number,
    to: number,
  ) {
    super('Reorder variables', from, to);
  }

  protected move(project: Project, from: number, to: number): void {
    if (!moveItem(requireVariableOwner(project, this.assetId).variables, from, to))
      throw new CommandError(`There is no variable ${from + 1} to move to place ${to + 1}`);
  }
}

/** The behavior, once it is known to declare `key`. */
function requireBehaviorVariable(project: Project, assetId: string, key: string): BehaviorAsset {
  const asset = requireBehavior(project, assetId);
  if (!asset.variables.some((v) => v.key === key)) throw new CommandError(`Variable "${key}" not found`);
  return asset;
}

/** Whether a behavior's variable carries on from one `Run behavior` call to the next (#229). */
export class SetVariableKeptCommand implements Command {
  readonly label: string;
  private previous = false;

  constructor(
    private readonly assetId: string,
    private readonly key: string,
    private readonly kept: boolean,
  ) {
    this.label = kept ? `Keep ${key} between calls` : `Reset ${key} every call`;
  }

  execute(project: Project): void {
    const asset = requireBehaviorVariable(project, this.assetId, this.key);
    this.previous = isKeptVariable(asset, this.key);
    setKeptVariable(asset, this.key, this.kept);
  }

  undo(project: Project): void {
    setKeptVariable(requireBehavior(project, this.assetId), this.key, this.previous);
  }
}

/**
 * Whether a behavior's variable is seen outside its own graph (#257). Going private drops the
 * overrides of every placed object: nobody would see them any more, yet they would still act.
 */
export class SetVariablePrivateCommand implements Command {
  readonly label: string;
  private previous = false;
  private overrides: TakenOverride[] = [];

  constructor(
    private readonly assetId: string,
    private readonly key: string,
    private readonly hidden: boolean,
  ) {
    this.label = hidden ? `Make ${key} private` : `Make ${key} public`;
  }

  execute(project: Project): void {
    const asset = requireBehaviorVariable(project, this.assetId, this.key);
    this.previous = isPrivateVariable(asset, this.key);
    setPrivateVariable(asset, this.key, this.hidden);
    this.overrides = this.hidden ? takeOverrides(project, this.assetId, this.key) : [];
  }

  undo(project: Project): void {
    setPrivateVariable(requireBehavior(project, this.assetId), this.key, this.previous);
    restoreOverrides(project, this.assetId, this.key, this.overrides);
  }
}

/**
 * A struct's fields are no properties of anything placed, so the reserved property names are free
 * there – as they are for a struct field.
 */
function isValidName(asset: VariableOwnerAsset, name: string): boolean {
  return asset.type === 'struct' ? isValidFieldName(name) : isValidVariableName(name);
}

const INVALID_NAME = 'Variable names must start with a letter and contain only letters, digits or _';
const INVALID_FIELD = 'Field names must start with a letter and contain only letters, digits or _';

/**
 * Where declared fields live: on a struct variable, or on a struct field of one, however deep
 * (#239). A list item carries its own shape instead.
 */
interface FieldOwner {
  fields(): readonly StructFieldDef[];
  setFields(next: readonly StructFieldDef[]): void;
}

function variableOf(project: Project, assetId: string, key: string): PropertyDef | undefined {
  return requireVariableOwner(project, assetId).variables.find((v) => v.key === key);
}

/** `path` names the struct fields from the variable down to the struct whose fields are meant. */
function requireFieldOwner(
  project: Project,
  assetId: string,
  key: string,
  path: readonly string[],
): FieldOwner {
  const def = variableOf(project, assetId, key);
  if (def?.kind !== 'struct') throw new CommandError(`Variable "${key}" has no fields`);
  if (fieldsAt(def.fields, path) === undefined)
    throw new CommandError(`Field "${path.join('.')}" has no fields`);
  return {
    fields: () => fieldsAt(def.fields, path) ?? [],
    setFields: (next) => (def.fields = withFieldsAt(def.fields, path, next)),
  };
}

function fieldsAt(
  fields: readonly StructFieldDef[],
  path: readonly string[],
): readonly StructFieldDef[] | undefined {
  if (path.length === 0) return fields;
  const field = fields.find((f) => f.key === path[0]);
  return field?.kind === 'struct' ? fieldsAt(field.fields, path.slice(1)) : undefined;
}

/** The declaration with the fields at `path` replaced, rebuilt on the way down. */
function withFieldsAt(
  fields: readonly StructFieldDef[],
  path: readonly string[],
  next: readonly StructFieldDef[],
): readonly StructFieldDef[] {
  if (path.length === 0) return next;
  return fields.map((f) =>
    f.key === path[0] && f.kind === 'struct'
      ? { ...f, fields: withFieldsAt(f.fields, path.slice(1), next) }
      : f,
  );
}

/**
 * One struct-carrying value of a variable (its declared default, the behavior's own, an override); a
 * field change hits all of them at once so none keeps a stale shape. `id` pairs a site up on undo.
 * With a `path` the site is the struct that deep inside the value.
 */
interface StructSite {
  id: string;
  read(): StructValue;
  write(value: StructValue): void;
}

function structSites(project: Project, assetId: string, key: string, path: readonly string[]): StructSite[] {
  const structIn = (value: PropertyValue | undefined): StructValue => {
    const at = valueAt(value, path);
    return isStruct(at) ? at : {};
  };
  return (
    valueHolders(project, assetId, key)
      // An override the object does not have stays absent: writing one here would invent a deviation.
      .filter((h) => !h.optional || isStruct(h.read()))
      .map((holder) => ({
        id: holder.id,
        read: () => structIn(holder.read()),
        write: (value: StructValue) => holder.write(withValueAt(holder.read(), path, value) ?? value),
      }))
  );
}

/** Everywhere one variable's value is kept: its declared default, the behavior's own, the overrides. */
interface ValueHolder {
  id: string;
  /** An override may simply not be there; the declared default and the behavior's own always are. */
  optional: boolean;
  read(): PropertyValue | undefined;
  write(value: PropertyValue): void;
}

function valueHolders(project: Project, assetId: string, key: string): ValueHolder[] {
  const asset = requireVariableOwner(project, assetId);
  const def = asset.variables.find((v) => v.key === key);
  const holders: ValueHolder[] = [];
  if (def)
    holders.push({
      id: 'declared',
      optional: false,
      read: () => def.default,
      write: (value) => {
        def.default = value;
      },
    });
  holders.push(bagHolder('asset', false, asset.props, key));
  for (const site of overrideSites(project, (id) => id === assetId))
    holders.push(bagHolder(`${site.object.id}/${site.path}`, true, site.bag, key));
  return holders;
}

function bagHolder(id: string, optional: boolean, bag: PropertyBag, key: string): ValueHolder {
  return { id, optional, read: () => bag[key], write: (value: PropertyValue) => (bag[key] = value) };
}

export class AddStructFieldCommand implements Command {
  readonly label: string;

  /** `path` names the struct the field is added to: none for the variable itself. */
  constructor(
    private readonly assetId: string,
    private readonly key: string,
    private readonly field: StructFieldDef,
    private readonly path: readonly string[] = [],
  ) {
    this.label = `Add field ${field.key}`;
  }

  execute(project: Project): void {
    const owner = requireFieldOwner(project, this.assetId, this.key, this.path);
    if (!isValidFieldName(this.field.key)) throw new CommandError(INVALID_FIELD);
    if (owner.fields().some((f) => f.key === this.field.key))
      throw new CommandError(`Field "${this.field.key}" already exists`);
    owner.setFields([...owner.fields(), { ...this.field }]);
    for (const site of structSites(project, this.assetId, this.key, this.path))
      site.write({ ...site.read(), [this.field.key]: emptyFieldValue(this.field) });
  }

  undo(project: Project): void {
    const owner = requireFieldOwner(project, this.assetId, this.key, this.path);
    owner.setFields(owner.fields().filter((f) => f.key !== this.field.key));
    for (const site of structSites(project, this.assetId, this.key, this.path))
      site.write(withoutField(site.read(), this.field.key));
  }
}

/** Takes the field's value out of every struct that carries it, and gives each one back on undo. */
export class RemoveStructFieldCommand implements Command {
  readonly label: string;
  private removed?: { field: Removed<StructFieldDef>; values: Map<string, FieldValue> };

  /** `path` names the struct the field is taken from: none for the variable itself. */
  constructor(
    private readonly assetId: string,
    private readonly key: string,
    private readonly field: string,
    private readonly path: readonly string[] = [],
  ) {
    this.label = `Remove field ${field}`;
  }

  execute(project: Project): void {
    const owner = requireFieldOwner(project, this.assetId, this.key, this.path);
    const fields = [...owner.fields()];
    const field = removeFirst(fields, (f) => f.key === this.field);
    if (!field) throw new CommandError(`Field "${this.field}" not found`);
    const values = new Map<string, FieldValue>();
    for (const site of structSites(project, this.assetId, this.key, this.path)) {
      const value = site.read();
      const item = value[this.field];
      if (item !== undefined) values.set(site.id, item);
      site.write(withoutField(value, this.field));
    }
    owner.setFields(fields);
    this.removed = { field, values };
  }

  undo(project: Project): void {
    if (!this.removed) return;
    const owner = requireFieldOwner(project, this.assetId, this.key, this.path);
    const fields = [...owner.fields()];
    restoreAt(fields, [this.removed.field]);
    owner.setFields(fields);
    for (const site of structSites(project, this.assetId, this.key, this.path)) {
      const value = this.removed.values.get(site.id);
      if (value !== undefined) site.write({ ...site.read(), [this.field]: value });
    }
  }
}

export class RenameStructFieldCommand extends RenameCommand {
  /** `path` names the struct the field belongs to: none for the variable itself. */
  constructor(
    private readonly assetId: string,
    private readonly key: string,
    from: string,
    to: string,
    private readonly path: readonly string[] = [],
  ) {
    super(`Rename field ${from}`, from, to);
  }

  protected rename(project: Project, from: string, to: string): void {
    const owner = requireFieldOwner(project, this.assetId, this.key, this.path);
    if (from === to) return;
    if (!isValidFieldName(to)) throw new CommandError(INVALID_FIELD);
    const fields = owner.fields();
    if (!fields.some((f) => f.key === from)) throw new CommandError(`Field "${from}" not found`);
    if (fields.some((f) => f.key === to)) throw new CommandError(`Field "${to}" already exists`);
    owner.setFields(fields.map((f) => (f.key === from ? { ...f, key: to } : f)));
    for (const site of structSites(project, this.assetId, this.key, this.path))
      site.write(withFieldRenamed(site.read(), from, to));
  }
}

/** A struct value is read by field name, so only the declaration changes order (#310). */
export class MoveStructFieldCommand extends MoveCommand {
  /** `path` names the struct whose fields are reordered: none for the variable itself. */
  constructor(
    private readonly assetId: string,
    private readonly key: string,
    from: number,
    to: number,
    private readonly path: readonly string[] = [],
  ) {
    super('Reorder fields', from, to);
  }

  protected move(project: Project, from: number, to: number): void {
    const owner = requireFieldOwner(project, this.assetId, this.key, this.path);
    const fields = [...owner.fields()];
    if (!moveItem(fields, from, to))
      throw new CommandError(`There is no field ${from + 1} to move to place ${to + 1}`);
    owner.setFields(fields);
  }
}