import type { AgentMessage } from "@oh-my-pi/pi-agent-core";
import type { ImageContent, MessageAttribution, ServiceTier, TextContent } from "@oh-my-pi/pi-ai";

export const CURRENT_SESSION_VERSION = 3;

export const EPHEMERAL_MODEL_CHANGE_ROLE = "fallback";

export interface SessionHeader {
	type: "session";
	version?: number; // v1 sessions don't have this
	id: string;
	title?: string; // Auto-generated title from first message
	titleSource?: "auto" | "user";
	timestamp: string;
	cwd: string;
	parentSession?: string;
}

export interface NewSessionOptions {
	parentSession?: string;
	/** Skip flushing the current session and delete it instead of saving. */
	drop?: boolean;
}

export interface SessionEntryBase {
	type: string;
	id: string;
	parentId: string | null;
	timestamp: string;
}

export interface SessionMessageEntry extends SessionEntryBase {
	type: "message";
	message: AgentMessage;
}

export interface ThinkingLevelChangeEntry extends SessionEntryBase {
	type: "thinking_level_change";
	thinkingLevel?: string | null;
	/**
	 * The user-configured selector at the time of this change: `"auto"` when auto
	 * mode was active, otherwise the concrete level. Absent on entries written
	 * before auto-mode persistence existed; readers fall back to `thinkingLevel`.
	 */
	configured?: string | null;
}

export interface ModelChangeEntry extends SessionEntryBase {
	type: "model_change";
	/** Model in "provider/modelId" format */
	model: string;
	/** Role: "default", "smol", "slow", etc. Undefined treated as "default" */
	role?: string;
}

export interface ServiceTierChangeEntry extends SessionEntryBase {
	type: "service_tier_change";
	serviceTier: ServiceTier | null;
}

export interface CompactionEntry<T = unknown> extends SessionEntryBase {
	type: "compaction";
	summary: string;
	shortSummary?: string;
	firstKeptEntryId: string;
	tokensBefore: number;
	/** Extension-specific data (e.g., ArtifactIndex, version markers for structured compaction) */
	details?: T;
	/** Hook-provided data to persist across compaction */
	preserveData?: Record<string, unknown>;
	/** True if generated by an extension, undefined/false if pi-generated (backward compatible) */
	fromExtension?: boolean;
}

export interface BranchSummaryEntry<T = unknown> extends SessionEntryBase {
	type: "branch_summary";
	fromId: string;
	summary: string;
	/** Extension-specific data (not sent to LLM) */
	details?: T;
	/** True if generated by an extension, false if pi-generated */
	fromExtension?: boolean;
}

/**
 * Custom entry for extensions to store extension-specific data in the session.
 * Use customType to identify your extension's entries.
 *
 * Purpose: Persist extension state across session reloads. On reload, extensions can
 * scan entries for their customType and reconstruct internal state.
 *
 * Does NOT participate in LLM context (ignored by buildSessionContext).
 * For injecting content into context, see CustomMessageEntry.
 */
export interface CustomEntry<T = unknown> extends SessionEntryBase {
	type: "custom";
	customType: string;
	data?: T;
}

/** Label entry for user-defined bookmarks/markers on entries. */
export interface LabelEntry extends SessionEntryBase {
	type: "label";
	targetId: string;
	label: string | undefined;
}

/** TTSR injection entry - tracks which time-traveling rules have been injected this session. */
export interface TtsrInjectionEntry extends SessionEntryBase {
	type: "ttsr_injection";
	/** Names of rules that were injected */
	injectedRules: string[];
}

/** Persisted MCP discovery selection state for a session branch. */
export interface MCPToolSelectionEntry extends SessionEntryBase {
	type: "mcp_tool_selection";
	/** MCP tool names selected for visibility in discovery mode. */
	selectedToolNames: string[];
}

/** Session init entry - captures initial context for subagent sessions (debugging/replay). */
export interface SessionInitEntry extends SessionEntryBase {
	type: "session_init";
	/** Full system prompt sent to the model */
	systemPrompt: string;
	/** Initial task/user message */
	task: string;
	/** Tools available to the agent */
	tools: string[];
	/** Output schema if structured output was requested */
	outputSchema?: unknown;
	/** Spawn allowlist the subagent ran with ("" = none, "*" = any, else CSV); absent on pre-spawns files. */
	spawns?: string;
	/** The agent's `readSummarize` setting (`false` = read summarization disabled); absent uses the session default. */
	readSummarize?: boolean;
}

/** Mode change entry - tracks agent mode transitions (e.g. plan mode). */
export interface ModeChangeEntry extends SessionEntryBase {
	type: "mode_change";
	/** Current mode name, or "none" when exiting a mode */
	mode: string;
	/** Optional mode-specific data (e.g. plan file path) */
	data?: Record<string, unknown>;
}

/**
 * Custom message entry for extensions to inject messages into LLM context.
 * Use customType to identify your extension's entries.
 *
 * Unlike CustomEntry, this DOES participate in LLM context.
 * The content participates in LLM context through convertToLlm().
 * Use details for extension-specific metadata (not sent to LLM).
 *
 * display controls TUI rendering:
 * - false: hidden entirely
 * - true: rendered with distinct styling (different from user messages)
 */
export interface CustomMessageEntry<T = unknown> extends SessionEntryBase {
	type: "custom_message";
	customType: string;
	content: string | (TextContent | ImageContent)[];
	details?: T;
	display: boolean;
	/** Who initiated this message for billing/attribution semantics. */
	attribution?: MessageAttribution;
}

/** Session entry - has id/parentId for tree structure (returned by "read" methods in SessionManager) */
export type SessionEntry =
	| SessionMessageEntry
	| ThinkingLevelChangeEntry
	| ModelChangeEntry
	| ServiceTierChangeEntry
	| CompactionEntry
	| BranchSummaryEntry
	| CustomEntry
	| CustomMessageEntry
	| LabelEntry
	| TtsrInjectionEntry
	| MCPToolSelectionEntry
	| SessionInitEntry
	| ModeChangeEntry;

/** Raw file entry (includes header) */
export type FileEntry = SessionHeader | SessionEntry;

/** Tree node for getTree() - defensive copy of session structure */
export interface SessionTreeNode {
	entry: SessionEntry;
	children: SessionTreeNode[];
	/** Resolved label for this entry, if any */
	label?: string;
}

export interface UsageStatistics {
	input: number;
	output: number;
	cacheRead: number;
	cacheWrite: number;
	premiumRequests: number;
	cost: number;
}