/**
 * Platform-neutral LineUp v1 protocol model.
 *
 * This module deliberately contains no DOM, network, Tauri, or storage code.
 * It is the boundary between untrusted transport payloads and the trusted
 * Interaction Kernel introduced in M0-03.
 */
export const LINEUP_PROTOCOL_VERSION = 1;

export type JsonPrimitive = string | number | boolean | null;
export type JsonValue = JsonPrimitive | JsonObject | JsonValue[];
export type JsonObject = { [key: string]: JsonValue };

export type ActorKind = "human" | "agent" | "app" | "system";

export type Actor = {
  kind: ActorKind;
  id: string;
};

/** A validated LineUp v1 wire envelope. */
export type Envelope = {
  v: typeof LINEUP_PROTOCOL_VERSION;
  id: string;
  type: string;
  conversation_id: string;
  sender: Actor;
  target?: Actor;
  /** ISO-8601 timestamp supplied by the producing adapter or client. */
  timestamp?: string;
  payload: JsonObject;
};

export type DeliveryState =
  | { status: "local_pending"; updated_at: string }
  | { status: "submitted"; updated_at: string; transport_id?: string }
  | { status: "delivered"; updated_at: string; transport_id?: string }
  | { status: "failed"; updated_at: string; error: string; retryable: boolean };

/** The only standard interaction requests admitted during Milestone 1. */
export type ToolCallKind = "choice" | "confirm" | "input";

export type ActionGroupMode = "single-choice" | "multi-choice" | "button";

export type ActionGroupAction = {
  id: string;
  label: string;
  description?: string;
};

export type ActionGroup = {
  mode: ActionGroupMode;
  actions: readonly ActionGroupAction[];
};

export type ConfirmDefinition = {
  approve_label: string;
  cancel_label: string;
};

export type InputFieldType = "text" | "textarea" | "number";

export type InputField = {
  id: string;
  label: string;
  type: InputFieldType;
  required: boolean;
  placeholder?: string;
  min_length?: number;
  max_length?: number;
  pattern?: string;
};

export type InputForm = {
  fields: readonly InputField[];
  submit_label: string;
  cancel_label: string;
};

export type ToolCallRequest = {
  call_id: string;
  tool: ToolCallKind;
  title: string;
  prompt: string;
  expires_at?: string;
  data: JsonObject;
  /** Present only for the trusted `choice` renderer introduced in M1-02. */
  action_group?: ActionGroup;
  /** Present only for the trusted `confirm` renderer introduced in M1-03. */
  confirm?: ConfirmDefinition;
  /** Present only for the trusted `input` renderer introduced in M1-03. */
  form?: InputForm;
};

export type ToolCallFinalStatus = "completed" | "failed" | "cancelled" | "expired";

export type ToolCallResult = {
  call_id: string;
  status: ToolCallFinalStatus;
  result: JsonObject;
  error?: string;
};

export type ToolCallCancel = {
  call_id: string;
  reason: string;
};

export type TaskStatus = "running" | "waiting" | "completed" | "failed" | "cancelled";

export type TaskProgress = {
  operation_id: string;
  title: string;
  percent: number;
  status: TaskStatus;
  cancellable: boolean;
};

/** Display-only, adapter-authoritative execution trace. It grants no ability. */
export type AgentExecutionStep = { id: string; title: string; status: "running" | "completed" | "failed" };
export type AgentExecutionTrace = { execution_id: string; status: "running" | "completed" | "failed"; steps: readonly AgentExecutionStep[] };

/**
 * A user-originated action awaiting delivery through the Transport Adapter.
 * It is data only: the Store owns retries and the Kernel owns state changes.
 */
export type UserAction =
  | {
      kind: "send-text";
      id: string;
      conversation_id: string;
      text: string;
      created_at: string;
      delivery: DeliveryState;
    }
  | {
      kind: "tool-result" | "tool-cancel";
      id: string;
      conversation_id: string;
      call_id: string;
      payload: JsonObject;
      created_at: string;
      delivery: DeliveryState;
    }
  | {
      kind: "surface-event";
      id: string;
      conversation_id: string;
      instance_id: string;
      event: string;
      data: JsonObject;
      created_at: string;
      delivery: DeliveryState;
    }
  | {
      kind: "app-result";
      id: string;
      conversation_id: string;
      call_id: string;
      payload: JsonObject;
      created_at: string;
      delivery: DeliveryState;
    };

export type ProtocolFallbackCode =
  | "invalid_json"
  | "invalid_envelope"
  | "unsupported_version"
  | "unsupported_type"
  | "invalid_payload";

/** Safe, displayable representation of content that must never be executed. */
export type ProtocolFallback = {
  code: ProtocolFallbackCode;
  /** A stable, non-sensitive diagnostic intended for logs and the fallback renderer. */
  detail: string;
  envelope?: Envelope;
};

type ConversationItemBase = {
  id?: string;
  envelope?: Envelope;
};

export type ConversationItem =
  | (ConversationItemBase & { kind: "user-message"; text: string; delivery: DeliveryState })
  | (ConversationItemBase & { kind: "markdown"; markdown: string; execution_id?: string })
  | (ConversationItemBase & { kind: "agent-status"; status: string; detail: string; execution_id?: string })
  | (ConversationItemBase & { kind: "execution-summary"; trace: AgentExecutionTrace })
  | (ConversationItemBase & { kind: "progress"; title: string; percent: number; status: string; task?: TaskProgress })
  | (ConversationItemBase & { kind: "error"; message: string; code?: string })
  | (ConversationItemBase & { kind: "tool-call"; call: ToolCallRequest })
  | (ConversationItemBase & { kind: "tool-result"; result: ToolCallResult })
  | (ConversationItemBase & { kind: "tool-cancel"; cancel: ToolCallCancel })
  | (ConversationItemBase & { kind: "surface"; envelope: Envelope })
  | (ConversationItemBase & { kind: "app-call"; envelope: Envelope })
  | (ConversationItemBase & { kind: "fallback"; reason: ProtocolFallbackCode; detail: string; envelope?: Envelope });

export type EnvelopeParseResult =
  | { ok: true; envelope: Envelope }
  | { ok: false; fallback: ProtocolFallback };

const ACTOR_KINDS = new Set<ActorKind>(["human", "agent", "app", "system"]);
const SUPPORTED_TYPES = new Set([
  "lineup.v1.text",
  "lineup.v1.agent.status",
  "lineup.v1.agent.execution",
  "lineup.v1.agent.progress",
  "lineup.v1.error",
  "lineup.v1.tool.call",
  "lineup.v1.tool.result",
  "lineup.v1.tool.cancel",
  "lineup.v1.ui.open",
  "lineup.v1.ui.patch",
  "lineup.v1.ui.close",
  "lineup.v1.app.call",
]);
const ID_MAX_LENGTH = 256;
const INSTANCE_ID = /^[A-Za-z0-9._:-]{1,128}$/;
const MESSAGE_TYPE = /^lineup\.v1\.[a-z][a-z0-9.]*[a-z0-9]$/;

function object(value: unknown): JsonObject | null {
  return value !== null && typeof value === "object" && !Array.isArray(value)
    ? (value as JsonObject)
    : null;
}

function isJsonValue(value: unknown, depth = 0): value is JsonValue {
  if (depth > 32 || value === null || typeof value === "string" || typeof value === "boolean") return depth <= 32;
  if (typeof value === "number") return Number.isFinite(value);
  if (Array.isArray(value)) return value.every(entry => isJsonValue(entry, depth + 1));
  if (value === null || typeof value !== "object") return false;
  const prototype = Object.getPrototypeOf(value);
  return (prototype === Object.prototype || prototype === null)
    && Object.values(value).every(entry => isJsonValue(entry, depth + 1));
}

function text(value: unknown): string {
  return typeof value === "string" ? value : "";
}

function identifier(value: unknown): string | null {
  return typeof value === "string" && value.trim().length > 0 && value.length <= ID_MAX_LENGTH
    ? value
    : null;
}

function parseActor(value: unknown): Actor | null {
  const candidate = object(value);
  const id = candidate && identifier(candidate.id);
  const kind = candidate?.kind;
  return id && typeof kind === "string" && ACTOR_KINDS.has(kind as ActorKind)
    ? { kind: kind as ActorKind, id }
    : null;
}

function fallback(code: ProtocolFallbackCode, detail: string, envelope?: Envelope): EnvelopeParseResult {
  return { ok: false, fallback: { code, detail, envelope } };
}

/**
 * Validates the shared envelope shape.  It intentionally does not dispatch a
 * message to a renderer or execute any request; that belongs to the Kernel.
 */
export function parseEnvelope(value: unknown): EnvelopeParseResult {
  const candidate = object(value);
  if (!candidate) return fallback("invalid_envelope", "Envelope must be a JSON object.");
  if (candidate.v !== LINEUP_PROTOCOL_VERSION) return fallback("unsupported_version", "Unsupported LineUp protocol version.");

  const id = identifier(candidate.id);
  const type = text(candidate.type);
  const conversationID = identifier(candidate.conversation_id);
  const sender = parseActor(candidate.sender);
  const payload = object(candidate.payload);
  if (!id || !MESSAGE_TYPE.test(type) || !conversationID || !sender || !payload || !isJsonValue(payload)) {
    return fallback("invalid_envelope", "Missing or invalid required LineUp envelope fields.");
  }

  let target: Actor | undefined;
  if (candidate.target !== undefined) {
    target = parseActor(candidate.target) ?? undefined;
    if (!target) return fallback("invalid_envelope", "Envelope target must be a valid actor.");
  }
  if (candidate.timestamp !== undefined && (typeof candidate.timestamp !== "string" || Number.isNaN(Date.parse(candidate.timestamp)))) {
    return fallback("invalid_envelope", "Envelope timestamp must be an ISO-8601 string.");
  }

  return {
    ok: true,
    envelope: {
      v: LINEUP_PROTOCOL_VERSION,
      id,
      type,
      conversation_id: conversationID,
      sender,
      ...(target ? { target } : {}),
      ...(candidate.timestamp !== undefined ? { timestamp: candidate.timestamp as string } : {}),
      payload,
    },
  };
}

/** Parses a JSON wire payload when callers do not support legacy plain text. */
export function parseEnvelopeJSON(raw: string): EnvelopeParseResult {
  try {
    return parseEnvelope(JSON.parse(raw));
  } catch {
    return fallback("invalid_json", "Transport payload is not valid JSON.");
  }
}

function validSurfacePayload(type: string, payload: JsonObject): boolean {
  const instanceID = text(payload.instance_id);
  if (!INSTANCE_ID.test(instanceID)) return false;
  if (type === "lineup.v1.ui.open") {
    if (!object(payload.app)) return false;
    return payload.state === undefined || object(payload.state) !== null;
  }
  if (type === "lineup.v1.ui.patch") return object(payload.state) !== null;
  return type === "lineup.v1.ui.close";
}

function validAppCallPayload(payload: JsonObject): boolean {
  return Boolean(identifier(payload.call_id) && identifier(payload.capability) && object(payload.arguments));
}

const TOOL_KINDS = new Set<ToolCallKind>(["choice", "confirm", "input"]);
const TOOL_FINAL_STATUSES = new Set<ToolCallFinalStatus>(["completed", "failed", "cancelled", "expired"]);
const ACTION_GROUP_MODES = new Set<ActionGroupMode>(["single-choice", "multi-choice", "button"]);
const INPUT_FIELD_TYPES = new Set<InputFieldType>(["text", "textarea", "number"]);
const TASK_STATUSES = new Set<TaskStatus>(["running", "waiting", "completed", "failed", "cancelled"]);
const EXECUTION_STATUSES = new Set(["running", "completed", "failed"]);

function optionalTimestamp(value: unknown): string | undefined {
  return typeof value === "string" && !Number.isNaN(Date.parse(value)) ? value : undefined;
}

function parseActionGroup(value: unknown): ActionGroup | undefined {
  const candidate = object(value);
  const mode = text(candidate?.mode) as ActionGroupMode;
  if (!candidate || !ACTION_GROUP_MODES.has(mode) || !Array.isArray(candidate.actions) || candidate.actions.length < 1 || candidate.actions.length > 12) return undefined;
  const seen = new Set<string>();
  const actions: ActionGroupAction[] = [];
  for (const value of candidate.actions) {
    const action = object(value);
    const id = action && identifier(action.id);
    const label = action && text(action.label).trim();
    const description = action ? text(action.description).trim() : "";
    if (!id || !label || label.length > 200 || seen.has(id)) return undefined;
    if (description.length > 500) return undefined;
    seen.add(id);
    actions.push({ id, label, ...(description ? { description } : {}) });
  }
  return { mode, actions };
}

function boundedLabel(value: unknown, fallback: string): string | undefined {
  const label = value === undefined ? fallback : text(value).trim();
  return label && label.length <= 80 ? label : undefined;
}

function parseConfirm(value: unknown): ConfirmDefinition | undefined {
  const candidate = object(value);
  if (!candidate) return undefined;
  const approve = boundedLabel(candidate.approve_label, "确认");
  const cancel = boundedLabel(candidate.cancel_label, "取消");
  return approve && cancel ? { approve_label: approve, cancel_label: cancel } : undefined;
}

function wholeNumber(value: unknown, maximum: number): number | undefined {
  return typeof value === "number" && Number.isSafeInteger(value) && value >= 0 && value <= maximum ? value : undefined;
}

function parseInputForm(value: unknown): InputForm | undefined {
  const candidate = object(value);
  if (!candidate || !Array.isArray(candidate.fields) || candidate.fields.length < 1 || candidate.fields.length > 8) return undefined;
  const seen = new Set<string>();
  const fields: InputField[] = [];
  for (const value of candidate.fields) {
    const field = object(value);
    const id = field && identifier(field.id);
    const label = field && text(field.label).trim();
    const type = field ? text(field.type) : "";
    const placeholder = field ? text(field.placeholder).trim() : "";
    const minLength = field?.min_length === undefined ? undefined : wholeNumber(field.min_length, 10_000);
    const maxLength = field?.max_length === undefined ? undefined : wholeNumber(field.max_length, 10_000);
    const pattern = field ? text(field.pattern) : "";
    if (!id || !label || label.length > 120 || !INPUT_FIELD_TYPES.has(type as InputFieldType) || seen.has(id) || placeholder.length > 200 || pattern.length > 256) return undefined;
    if ((field?.min_length !== undefined && minLength === undefined) || (field?.max_length !== undefined && maxLength === undefined) || (minLength !== undefined && maxLength !== undefined && minLength > maxLength)) return undefined;
    if (pattern) {
      try { new RegExp(pattern, "u"); } catch { return undefined; }
    }
    seen.add(id);
    fields.push({
      id,
      label,
      type: type as InputFieldType,
      required: field?.required === true,
      ...(placeholder ? { placeholder } : {}),
      ...(minLength !== undefined ? { min_length: minLength } : {}),
      ...(maxLength !== undefined ? { max_length: maxLength } : {}),
      ...(pattern ? { pattern } : {}),
    });
  }
  const submit = boundedLabel(candidate.submit_label, "提交");
  const cancel = boundedLabel(candidate.cancel_label, "取消");
  return submit && cancel ? { fields, submit_label: submit, cancel_label: cancel } : undefined;
}

function parseToolCall(payload: JsonObject): ToolCallRequest | undefined {
  const callID = identifier(payload.call_id);
  const tool = text(payload.tool) as ToolCallKind;
  if (!callID || !TOOL_KINDS.has(tool)) return undefined;
  const expiresAt = optionalTimestamp(payload.expires_at);
  if (payload.expires_at !== undefined && !expiresAt) return undefined;
  const data = payload.data === undefined ? {} : object(payload.data);
  if (!data) return undefined;
  const actionGroup = tool === "choice" ? parseActionGroup(data.action_group) : undefined;
  const confirm = tool === "confirm" ? parseConfirm(data.confirm) : undefined;
  const form = tool === "input" ? parseInputForm(data.form) : undefined;
  if (tool === "choice" && !actionGroup) return undefined;
  if (tool === "confirm" && !confirm) return undefined;
  if (tool === "input" && !form) return undefined;
  return {
    call_id: callID,
    tool,
    title: text(payload.title),
    prompt: text(payload.prompt),
    ...(expiresAt ? { expires_at: expiresAt } : {}),
    data,
    ...(actionGroup ? { action_group: actionGroup } : {}),
    ...(confirm ? { confirm } : {}),
    ...(form ? { form } : {}),
  };
}

function parseTaskProgress(payload: JsonObject, percent: number): TaskProgress | undefined {
  const operationID = identifier(payload.operation_id);
  const status = text(payload.status) as TaskStatus;
  if (!operationID || !TASK_STATUSES.has(status)) return undefined;
  const title = text(payload.title).trim();
  if (!title || title.length > 200) return undefined;
  return { operation_id: operationID, title, percent, status, cancellable: payload.cancellable === true };
}

function parseExecutionTrace(payload: JsonObject): AgentExecutionTrace | undefined {
  const executionID = identifier(payload.execution_id);
  const status = text(payload.status);
  if (!executionID || !EXECUTION_STATUSES.has(status) || !Array.isArray(payload.steps) || payload.steps.length > 12) return undefined;
  const steps: AgentExecutionStep[] = [];
  const seen = new Set<string>();
  for (const raw of payload.steps) {
    const step = object(raw);
    const id = step && identifier(step.id);
    const title = step && text(step.title).trim();
    const stepStatus = step && text(step.status);
    if (!id || !title || title.length > 160 || !stepStatus || !EXECUTION_STATUSES.has(stepStatus) || seen.has(id)) return undefined;
    seen.add(id);
    steps.push({ id, title, status: stepStatus as AgentExecutionStep["status"] });
  }
  return { execution_id: executionID, status: status as AgentExecutionTrace["status"], steps };
}

function parseToolResult(payload: JsonObject): ToolCallResult | undefined {
  const callID = identifier(payload.call_id);
  const status = text(payload.status) as ToolCallFinalStatus;
  const result = payload.result === undefined ? {} : object(payload.result);
  if (!callID || !TOOL_FINAL_STATUSES.has(status) || !result) return undefined;
  return { call_id: callID, status, result, ...(text(payload.error) ? { error: text(payload.error) } : {}) };
}

function parseToolCancel(payload: JsonObject): ToolCallCancel | undefined {
  const callID = identifier(payload.call_id);
  return callID ? { call_id: callID, reason: text(payload.reason) } : undefined;
}

function fallbackItem(value: ProtocolFallback): ConversationItem {
  return {
    kind: "fallback",
    reason: value.code,
    detail: value.detail,
    ...(value.envelope ? { id: value.envelope.id, envelope: value.envelope } : {}),
  };
}

/**
 * Converts an untrusted transport payload into a trusted renderer model.
 * Plain legacy text remains a Markdown item for backwards compatibility;
 * malformed JSON and invalid LineUp envelopes are always safe fallbacks.
 */
export function decodeConversationItem(raw: string): ConversationItem {
  let parsed: unknown;
  try {
    parsed = JSON.parse(raw);
  } catch {
    return { kind: "markdown", markdown: raw };
  }

  const parsedEnvelope = parseEnvelope(parsed);
  if (!parsedEnvelope.ok) return fallbackItem(parsedEnvelope.fallback);
  const envelope = parsedEnvelope.envelope;
  const payload = envelope.payload;
  const base = { id: envelope.id, envelope };

  if (!SUPPORTED_TYPES.has(envelope.type)) {
    return fallbackItem({ code: "unsupported_type", detail: `Unsupported LineUp message type: ${envelope.type}`, envelope });
  }

  switch (envelope.type) {
    case "lineup.v1.text": {
      const markdown = text(payload.markdown) || text(payload.text);
      return markdown
        ? { kind: "markdown", markdown, ...(identifier(payload.execution_id) ? { execution_id: identifier(payload.execution_id)! } : {}), ...base }
        : fallbackItem({ code: "invalid_payload", detail: "Text payload requires text or markdown.", envelope });
    }
    case "lineup.v1.agent.status": {
      const status = text(payload.status);
      return status
        ? { kind: "agent-status", status, detail: text(payload.detail), ...(identifier(payload.execution_id) ? { execution_id: identifier(payload.execution_id)! } : {}), ...base }
        : fallbackItem({ code: "invalid_payload", detail: "Agent status payload requires status.", envelope });
    }
    case "lineup.v1.agent.execution": {
      const trace = parseExecutionTrace(payload);
      return trace ? { kind: "execution-summary", trace, ...base } : fallbackItem({ code: "invalid_payload", detail: "Agent execution requires bounded public steps.", envelope });
    }
    case "lineup.v1.agent.progress": {
      const percent = payload.percent;
      if (typeof percent !== "number" || !Number.isFinite(percent) || percent < 0 || percent > 100) {
        return fallbackItem({ code: "invalid_payload", detail: "Agent progress payload requires percent between 0 and 100.", envelope });
      }
      const task = payload.operation_id === undefined ? undefined : parseTaskProgress(payload, percent);
      if (payload.operation_id !== undefined && !task) return fallbackItem({ code: "invalid_payload", detail: "Task progress requires operation_id, title, supported status, and valid cancellation flag.", envelope });
      return { kind: "progress", title: text(payload.title), percent, status: text(payload.status), ...(task ? { task } : {}), ...base };
    }
    case "lineup.v1.error": {
      const message = text(payload.message);
      return message
        ? { kind: "error", message, ...(text(payload.code) ? { code: text(payload.code) } : {}), ...base }
        : fallbackItem({ code: "invalid_payload", detail: "Error payload requires message.", envelope });
    }
    case "lineup.v1.tool.call": {
      const call = parseToolCall(payload);
      return call ? { kind: "tool-call", call, ...base } : fallbackItem({ code: "invalid_payload", detail: "Tool call requires call_id, supported tool, and JSON data.", envelope });
    }
    case "lineup.v1.tool.result": {
      const result = parseToolResult(payload);
      return result ? { kind: "tool-result", result, ...base } : fallbackItem({ code: "invalid_payload", detail: "Tool result requires call_id, final status, and JSON result.", envelope });
    }
    case "lineup.v1.tool.cancel": {
      const cancel = parseToolCancel(payload);
      return cancel ? { kind: "tool-cancel", cancel, ...base } : fallbackItem({ code: "invalid_payload", detail: "Tool cancel requires call_id.", envelope });
    }
    case "lineup.v1.ui.open":
    case "lineup.v1.ui.patch":
    case "lineup.v1.ui.close":
      return validSurfacePayload(envelope.type, payload)
        ? { kind: "surface", ...base }
        : fallbackItem({ code: "invalid_payload", detail: "Surface payload does not match its lifecycle contract.", envelope });
    case "lineup.v1.app.call":
      return validAppCallPayload(payload)
        ? { kind: "app-call", ...base }
        : fallbackItem({ code: "invalid_payload", detail: "App call payload requires call_id, capability, and arguments.", envelope });
    default:
      return fallbackItem({ code: "unsupported_type", detail: `Unsupported LineUp message type: ${envelope.type}`, envelope });
  }
}