import { Type } from "@sinclair/typebox";
import type { ExtensionAPI, ExtensionContext } from "../_shared/pi-api.js";
import { getProjectRoot, textResult } from "../_shared/pi-api.js";
import { validateParams } from "../_shared/validation.js";
import { applyPreview, discardPreview, getLatestPendingPreview, getPreview } from "../_shared/ast-engine.js";
import { emitDevEvent } from "../_shared/event-bus.js";

const AstApplyParams = Type.Object({
  action: Type.Union([Type.Literal("apply"), Type.Literal("discard")], { description: "Preview lifecycle action" }),
  previewId: Type.String({ description: "Preview id returned by ast_edit" }),
  reason: Type.Optional(Type.String({ description: "Why applying or discarding the preview", maxLength: 500 })),
});

const ResolveParams = Type.Object({
  action: Type.Union([Type.Literal("apply"), Type.Literal("discard")], { description: "Whether to apply or discard the pending preview" }),
  reason: Type.String({ description: "Why applying or discarding the pending preview", maxLength: 500 }),
  extra: Type.Optional(Type.Object({
    previewId: Type.Optional(Type.String({ description: "Preview id returned by ast_edit. Optional; resolve defaults to the latest pending AST preview." })),
  }, { additionalProperties: true, description: "Free-form resolve metadata" })),
});

export default function astApplyTool(pi: ExtensionAPI): void {
  pi.registerTool({
    name: "ast_apply",
    description: "Legacy alias for resolve over ast_edit previews. Prefer resolve for new AST preview finalization.",
    parameters: AstApplyParams,
    async execute(_toolCallId, params, _signal, _update, ctx) {
      const valid = validateParams(AstApplyParams, params);
      if (!valid.ok) return valid.result;
      return finalizePreview(valid.value.previewId, valid.value.action, valid.value.reason ?? "", ctx, "ast_apply");
    },
  });

  pi.registerTool({
    name: "resolve",
    description: "Resolve a pending ast_edit preview by applying or discarding it.",
    parameters: ResolveParams,
    async execute(_toolCallId, params, _signal, _update, ctx) {
      const valid = validateParams(ResolveParams, params);
      if (!valid.ok) return valid.result;
      const previewId = valid.value.extra?.previewId ?? getLatestPendingPreview(getProjectRoot(ctx))?.id;
      if (!previewId) return { isError: true, content: [{ type: "text", text: "No pending action to resolve. Nothing to apply or discard." }] };
      return finalizePreview(previewId, valid.value.action, valid.value.reason, ctx, "resolve");
    },
  });
}

async function finalizePreview(
  previewId: string,
  action: "apply" | "discard",
  reason: string,
  ctx: ExtensionContext,
  sourceToolName: "resolve" | "ast_apply",
) {
  const preview = getPreview(previewId);
  if (!preview) return { isError: true, content: [{ type: "text" as const, text: `Unknown preview: ${previewId}` }] };
  if (action === "discard") {
    discardPreview(previewId);
    emitDevEvent(`${sourceToolName}:discard`, { previewId, reason });
    return textResult(`Discarded ${previewId}`, resolveDetails(action, reason, previewId, sourceToolName));
  }
  const result = await applyPreview(previewId, getProjectRoot(ctx));
  if (result.stale.length) {
    emitDevEvent(`${sourceToolName}:stale`, { previewId, files: result.stale.length });
    return {
      isError: true,
      content: [{ type: "text" as const, text: `Preview is stale; refusing apply:\n${result.stale.join("\n")}` }],
      details: { ...resolveDetails(action, reason, previewId, sourceToolName), stale: result.stale },
    };
  }
  emitDevEvent(`${sourceToolName}:apply`, { previewId, files: result.applied });
  return textResult(`Applied ${previewId} to ${result.applied} files`, {
    ...resolveDetails(action, reason, previewId, sourceToolName),
    filesApplied: result.applied,
  });
}

function resolveDetails(action: "apply" | "discard", reason: string, previewId: string, sourceToolName: "resolve" | "ast_apply") {
  return {
    action,
    reason,
    sourceToolName,
    label: `ast_edit preview ${previewId}`,
    extra: { previewId },
    sourceResultDetails: { previewId },
  };
}