/**
 * Hook implementations for the Hindsight OpenCode plugin.
 *
 * Hooks:
 *   - event (session.created) → recall memories and inject into system prompt
 *   - event (session.idle) → auto-retain conversation transcript
 *   - experimental.session.compacting → inject memories into compaction context
 */

import type { HindsightClient } from '@vectorize-io/hindsight-client';
import type { HindsightConfig } from './config.js';
import { debugLog } from './config.js';
import {
    formatMemories,
    formatCurrentTime,
    stripMemoryTags,
    composeRecallQuery,
    truncateRecallQuery,
    prepareRetentionTranscript,
    sliceLastTurnsByUserBoundary,
    type Message,
} from './content.js';
import { ensureBankMission } from './bank.js';

export interface PluginState {
    turnCount: number;
    missionsSet: Set<string>;
    /** Track sessions we've already injected recall into */
    recalledSessions: Set<string>;
    /** Track last retained turn count per session to avoid duplicates */
    lastRetainedTurn: Map<string, number>;
}

interface EventInput {
    event: {
        type: string;
        properties: Record<string, unknown>;
    };
}

interface CompactingInput {
    sessionID: string;
}

interface CompactingOutput {
    context: string[];
    prompt?: string;
}

interface SystemTransformInput {
    sessionID?: string;
    model: unknown;
}

interface SystemTransformOutput {
    system: string[];
}

type OpencodeClient = {
    session: {
        messages: (opts: { path: { id: string } }) => Promise<{ data?: Array<{ role: string; parts?: Array<{ type: string; text?: string }> }> }>;
    };
};

export interface HindsightHooks {
    event: (input: EventInput) => Promise<void>;
    'experimental.session.compacting': (
        input: CompactingInput,
        output: CompactingOutput,
    ) => Promise<void>;
    'experimental.chat.system.transform': (
        input: SystemTransformInput,
        output: SystemTransformOutput,
    ) => Promise<void>;
}

export function createHooks(
    hindsightClient: HindsightClient,
    bankId: string,
    config: HindsightConfig,
    state: PluginState,
    opencodeClient: OpencodeClient,
): HindsightHooks {
    interface RecallOutcome {
        /** formatted context string, or null if no results */
        context: string | null;
        /** true if the API call succeeded (even with 0 results) */
        ok: boolean;
    }

    /** Recall memories and format as context string */
    async function recallForContext(query: string): Promise<RecallOutcome> {
        try {
            const response = await hindsightClient.recall(bankId, query, {
                budget: config.recallBudget as 'low' | 'mid' | 'high',
                maxTokens: config.recallMaxTokens,
                types: config.recallTypes,
            });

            const results = response.results || [];
            if (!results.length) return { context: null, ok: true };

            const formatted = formatMemories(results);
            const context =
                `<hindsight_memories>\n` +
                `${config.recallPromptPreamble}\n` +
                `Current time: ${formatCurrentTime()} UTC\n\n` +
                `${formatted}\n` +
                `</hindsight_memories>`;
            return { context, ok: true };
        } catch (e) {
            debugLog(config, 'Recall failed:', e);
            return { context: null, ok: false };
        }
    }

    /** Extract plain-text messages from an OpenCode session */
    async function getSessionMessages(sessionId: string): Promise<Message[]> {
        try {
            const response = await opencodeClient.session.messages({
                path: { id: sessionId },
            });
            const rawMessages = response.data || [];
            const messages: Message[] = [];
            for (const msg of rawMessages) {
                const role = msg.role;
                if (role !== 'user' && role !== 'assistant') continue;
                const textParts = (msg.parts || [])
                    .filter((p: { type: string; text?: string }) => p.type === 'text' && p.text)
                    .map((p: { type: string; text?: string }) => p.text!);
                if (textParts.length) {
                    messages.push({ role, content: textParts.join('\n') });
                }
            }
            return messages;
        } catch (e) {
            debugLog(config, 'Failed to get session messages:', e);
            return [];
        }
    }

    /**
     * Retain messages for a session, respecting retainMode and documentId semantics.
     * Used by both idle-retain and pre-compaction retain.
     */
    async function retainSession(sessionId: string, messages: Message[]): Promise<void> {
        const retainFullWindow = config.retainMode === 'full-session';
        let targetMessages: Message[];
        let documentId: string;

        if (retainFullWindow) {
            targetMessages = messages;
            // Full-session upserts the same document each time
            documentId = sessionId;
        } else {
            // Sliding window: retainEveryNTurns + overlap
            const windowTurns = config.retainEveryNTurns + config.retainOverlapTurns;
            targetMessages = sliceLastTurnsByUserBoundary(messages, windowTurns);
            // Chunked mode: unique document per chunk
            documentId = `${sessionId}-${Date.now()}`;
        }

        const { transcript } = prepareRetentionTranscript(targetMessages, true);
        if (!transcript) return;

        await ensureBankMission(hindsightClient, bankId, config, state.missionsSet);
        await hindsightClient.retain(bankId, transcript, {
            documentId,
            context: config.retainContext,
            tags: config.retainTags.length ? config.retainTags : undefined,
            metadata: Object.keys(config.retainMetadata).length
                ? { ...config.retainMetadata, session_id: sessionId }
                : { session_id: sessionId },
            async: true,
        });
    }

    /** Auto-retain conversation transcript */
    async function handleSessionIdle(sessionId: string): Promise<void> {
        if (!config.autoRetain) return;

        const messages = await getSessionMessages(sessionId);
        if (!messages.length) return;

        // Count user turns
        const userTurns = messages.filter((m) => m.role === 'user').length;
        const lastRetained = state.lastRetainedTurn.get(sessionId) || 0;

        // Only retain if enough new turns since last retain
        if (userTurns - lastRetained < config.retainEveryNTurns) return;

        try {
            await retainSession(sessionId, messages);
            state.lastRetainedTurn.set(sessionId, userTurns);
            debugLog(config, `Auto-retained ${messages.length} messages for session ${sessionId}`);
        } catch (e) {
            debugLog(config, 'Auto-retain failed:', e);
        }
    }

    const event = async (input: EventInput): Promise<void> => {
        try {
            const { event: evt } = input;

            if (evt.type === 'session.idle') {
                const sessionId = (evt.properties as { sessionID?: string }).sessionID;
                if (sessionId) {
                    await handleSessionIdle(sessionId);
                }
            }

            if (evt.type === 'session.created') {
                const session = evt.properties.info as { id?: string; title?: string } | undefined;
                const sessionId = session?.id;
                if (sessionId && config.autoRecall && !state.recalledSessions.has(sessionId)) {
                    state.recalledSessions.add(sessionId);
                    // Cap tracked sessions
                    if (state.recalledSessions.size > 1000) {
                        const first = state.recalledSessions.values().next().value;
                        if (first) state.recalledSessions.delete(first);
                    }
                }
            }
        } catch (e) {
            debugLog(config, 'Event hook error:', e);
        }
    };

    const compacting = async (
        input: CompactingInput,
        output: CompactingOutput,
    ): Promise<void> => {
        try {
            // First, retain what we have before compaction (using shared retention logic)
            const messages = await getSessionMessages(input.sessionID);
            if (messages.length && config.autoRetain) {
                try {
                    await retainSession(input.sessionID, messages);
                    debugLog(config, 'Pre-compaction retain completed');
                } catch (e) {
                    debugLog(config, 'Pre-compaction retain failed:', e);
                }
            }

            // Then recall relevant memories to inject into compaction context
            if (messages.length) {
                const lastUserMsg = [...messages].reverse().find((m) => m.role === 'user');
                if (lastUserMsg) {
                    const query = composeRecallQuery(
                        lastUserMsg.content,
                        messages,
                        config.recallContextTurns,
                    );
                    const truncated = truncateRecallQuery(
                        query,
                        lastUserMsg.content,
                        config.recallMaxQueryChars,
                    );
                    const { context } = await recallForContext(truncated);
                    if (context) {
                        output.context.push(context);
                    }
                }
            }
        } catch (e) {
            debugLog(config, 'Compaction hook error:', e);
        }
    };

    const systemTransform = async (
        input: SystemTransformInput,
        output: SystemTransformOutput,
    ): Promise<void> => {
        try {
            if (!config.autoRecall) return;
            const sessionId = input.sessionID;
            if (!sessionId) return;

            // Only inject on first message of a session (tracked by recalledSessions)
            if (!state.recalledSessions.has(sessionId)) return;

            await ensureBankMission(hindsightClient, bankId, config, state.missionsSet);

            // Use a generic project-context query for session start
            const query = `project context and recent work`;
            const { context, ok } = await recallForContext(query);

            // Consume after a successful API round-trip (even with 0 results).
            // Only preserve retry for transient API failures (ok=false).
            if (ok) {
                state.recalledSessions.delete(sessionId);
            }

            if (context) {
                output.system.push(context);
                debugLog(config, `Injected recall context for session ${sessionId}`);
            }
        } catch (e) {
            debugLog(config, 'System transform hook error:', e);
        }
    };

    return {
        event,
        'experimental.session.compacting': compacting,
        'experimental.chat.system.transform': systemTransform,
    };
}