import type { Asset } from '../model/Asset';
import type { PropertyBag, PropertyValue } from '../model/Properties';
import type { Project } from '../model/Project';
import { isGlobal } from '../model/Scope';
import type { PropertyDef } from '../properties/PropertySchema';
import type { NodeContext, SharedState } from './NodeContext';

export function emptySharedState(): SharedState {
  return { variables: {}, states: {} };
}

/**
 * Built once per run, from the declarations rather than from any instance: a global variable exists
 * even before the behavior declaring it is placed. Two behaviors declaring the same name mean the
 * same variable – the first declaration sets the starting value (see `globalConflicts`).
 */
export function buildSharedState(project: Project): SharedState {
  const shared = emptySharedState();
  for (const asset of project.assets) {
    if (asset.type === 'behavior') {
      for (const def of asset.variables)
        if (isGlobal(def) && !(def.key in shared.variables))
          shared.variables[def.key] = asset.props[def.key] ?? def.default;
    } else if (asset.type === 'statemachine' && isGlobal(asset)) {
      shared.states[asset.id] = '';
    }
  }
  return shared;
}

/**
 * Where two behaviors disagree about the same global name. A different kind is an error – one of the
 * two would silently read a value of a type it never declared – while a different starting value is
 * only a warning, since the first declaration decides and the run is well defined either way.
 */
export interface GlobalConflict {
  key: string;
  severity: 'error' | 'warning';
  message: string;
}

export function globalConflicts(project: Project): GlobalConflict[] {
  const first = new Map<string, { def: PropertyDef; asset: string; value: PropertyValue }>();
  const conflicts: GlobalConflict[] = [];
  const seen = new Set<string>();
  for (const asset of project.assets) {
    if (asset.type !== 'behavior') continue;
    for (const def of asset.variables) {
      if (!isGlobal(def)) continue;
      const value = asset.props[def.key] ?? def.default;
      const held = first.get(def.key);
      if (!held) {
        first.set(def.key, { def, asset: asset.name, value });
        continue;
      }
      // One report per name: a third behavior disagreeing adds nothing the first line does not say.
      if (seen.has(def.key)) continue;
      if (held.def.kind !== def.kind) {
        seen.add(def.key);
        conflicts.push({
          key: def.key,
          severity: 'error',
          message: `Global variable "${def.key}" is a ${held.def.kind} in ${held.asset} and a ${def.kind} in ${asset.name}.`,
        });
      } else if (!sameValue(held.value, value)) {
        seen.add(def.key);
        conflicts.push({
          key: def.key,
          severity: 'warning',
          message: `Global variable "${def.key}" starts at ${display(held.value)} in ${held.asset} and at ${display(value)} in ${asset.name}; the first is used.`,
        });
      }
    }
  }
  return conflicts;
}

/** Structs and lists compare by their stored shape, which is what the project file holds anyway. */
function sameValue(a: PropertyValue | undefined, b: PropertyValue | undefined): boolean {
  return a === b || JSON.stringify(a ?? null) === JSON.stringify(b ?? null);
}

function display(value: PropertyValue | undefined): string {
  return typeof value === 'string' ? `"${value}"` : JSON.stringify(value ?? null);
}

/** The bag a variable is written to: its own when the behavior declares it, else the shared one. */
export function variableBag(ctx: NodeContext, key: string): PropertyBag {
  if (key in ctx.variables) return ctx.variables;
  return key in ctx.shared.variables ? ctx.shared.variables : ctx.variables;
}

/** Everything the behavior can read under one name, its own declaration winning over a shared one. */
export function readableVariables(ctx: NodeContext): PropertyBag {
  const shared = ctx.shared.variables;
  return isEmpty(shared) ? ctx.variables : { ...shared, ...ctx.variables };
}

/** Where a machine's current state is kept: shared when the machine is `global`, else per instance. */
export function stateBag(ctx: NodeContext, machineId: string): Record<string, string> {
  return machineId in ctx.shared.states ? ctx.shared.states : ctx.states;
}

/** The defaults a behavior instance starts with: a shared variable is not one of them. */
export function withoutGlobals(defaults: PropertyBag, asset: Asset): PropertyBag {
  if (asset.type !== 'behavior') return defaults;
  const own = { ...defaults };
  for (const def of asset.variables) if (isGlobal(def)) delete own[def.key];
  return own;
}

function isEmpty(bag: PropertyBag): boolean {
  for (const key in bag) if (Object.hasOwn(bag, key)) return false;
  return true;
}