import * as fs from 'fs/promises';
import * as path from 'path';
import { randomUUID } from 'crypto';
import type {
  SessionMeta,
  Message,
  GroupMeta,
  MessageCost,
  JnlSessionHeader,
  JnlEntry,
  JnlMessageEntry,
  JnlSessionInfoEntry,
  JnlTextContent,
  JnlToolCall,
  SessionIndex,
  SessionIndexEntry,
} from './types';

// ── Path helpers ───────────────────────────────────────────────────────

const SESSIONS_ROOT = '.pi/agent/sessions';
const OFFICER_DIR = '.officer';
const INDEX_FILE = 'index.json';
const GROUPS_DIR = 'groups';

function getSessionsDir(baseCwd: string): string {
  return path.join(baseCwd, SESSIONS_ROOT);
}

function getOfficerDir(baseCwd: string): string {
  return path.join(baseCwd, SESSIONS_ROOT, OFFICER_DIR);
}

function getIndexPath(baseCwd: string): string {
  return path.join(getOfficerDir(baseCwd), INDEX_FILE);
}

function getGroupsDir(baseCwd: string): string {
  return path.join(getOfficerDir(baseCwd), GROUPS_DIR);
}

function getGroupPath(baseCwd: string, groupSlug: string): string {
  return path.join(getGroupsDir(baseCwd), `${groupSlug}.json`);
}

export function encodeCwdDir(cwd: string): string {
  return cwd.replace(/\//g, '-');
}

function buildJnlFilename(createdAt: number, sessionId: string): string {
  return `${createdAt}_${sessionId}.jsonl`;
}

function buildRelativePath(cwd: string, createdAt: number, sessionId: string): string {
  return path.join(encodeCwdDir(cwd), buildJnlFilename(createdAt, sessionId));
}

// ── Hex ID generator ───────────────────────────────────────────────────

export function generateHexId(): string {
  const bytes = new Uint8Array(4);
  crypto.getRandomValues(bytes);
  return Array.from(bytes)
    .map((b) => b.toString(16).padStart(2, '0'))
    .join('');
}

// ── JSONL serialization ────────────────────────────────────────────────

function serializeJnlFile(header: JnlSessionHeader, entries: JnlEntry[]): string {
  const lines = [JSON.stringify(header)];
  for (const entry of entries) {
    lines.push(JSON.stringify(entry));
  }
  return lines.join('\n') + '\n';
}

function parseJnlFile(content: string): { header: JnlSessionHeader; entries: JnlEntry[] } {
  const lines = content.trim().split('\n');
  if (lines.length === 0) {
    throw new Error('Empty JSONL file');
  }

  const header = JSON.parse(lines[0]!) as JnlSessionHeader;
  const entries: JnlEntry[] = [];

  for (let i = 1; i < lines.length; i++) {
    const line = lines[i]!.trim();
    if (!line) continue;
    entries.push(JSON.parse(line) as JnlEntry);
  }

  return { header, entries };
}

// ── Index management ───────────────────────────────────────────────────

async function loadIndex(baseCwd: string): Promise<SessionIndex> {
  try {
    const indexPath = getIndexPath(baseCwd);
    const content = await fs.readFile(indexPath, 'utf-8');
    return JSON.parse(content) as SessionIndex;
  } catch {
    return {};
  }
}

async function saveIndex(baseCwd: string, index: SessionIndex): Promise<void> {
  const officerDir = getOfficerDir(baseCwd);
  await fs.mkdir(officerDir, { recursive: true });
  const indexPath = getIndexPath(baseCwd);
  await fs.writeFile(indexPath, JSON.stringify(index, null, 2));
}

// ── Message ↔ JSONL conversion ─────────────────────────────────────────

export function messagesToJnlEntries(messages: Message[], meta: SessionMeta): JnlEntry[] {
  const entries: JnlEntry[] = [];
  let prevId: string | undefined;
  let i = 0;

  while (i < messages.length) {
    const msg = messages[i]!;

    if (msg.role === 'user') {
      const id = generateHexId();
      const entry: JnlMessageEntry = {
        type: 'message',
        id,
        parentId: prevId,
        timestamp: new Date(msg.timestamp).toISOString(),
        message: { role: 'user', content: [{ type: 'text' as const, text: msg.text ?? '' }] },
      };
      entries.push(entry);
      prevId = id;
      i++;
    } else if (msg.role === 'assistant') {
      const content: Array<JnlTextContent | JnlToolCall> = [];
      if (msg.text) {
        content.push({ type: 'text', text: msg.text });
      }

      // Collect following tool messages
      const toolMessages: Message[] = [];
      let j = i + 1;
      while (j < messages.length && messages[j]!.role === 'tool') {
        const toolMsg = messages[j]!;
        content.push({
          type: 'tool_use',
          id: toolMsg.toolCallId ?? generateHexId(),
          name: toolMsg.toolName ?? 'unknown',
          input: toolMsg.toolInput ?? {},
        });
        toolMessages.push(toolMsg);
        j++;
      }

      const assistId = generateHexId();
      const assistEntry: JnlMessageEntry = {
        type: 'message',
        id: assistId,
        parentId: prevId,
        timestamp: new Date(msg.timestamp).toISOString(),
        message: { role: 'assistant', content },
      };
      entries.push(assistEntry);
      prevId = assistId;

      // Emit toolResult entries for tools with output
      for (const toolMsg of toolMessages) {
        if (toolMsg.output !== undefined) {
          const trId = generateHexId();
          const trEntry: JnlMessageEntry = {
            type: 'message',
            id: trId,
            parentId: prevId,
            timestamp: new Date(toolMsg.timestamp).toISOString(),
            message: {
              role: 'toolResult',
              toolCallId: toolMsg.toolCallId ?? '',
              toolName: toolMsg.toolName ?? 'unknown',
              content: [{ type: 'text', text: toolMsg.output }],
              isError: toolMsg.isError,
            },
          };
          entries.push(trEntry);
          prevId = trId;
        }
      }

      i = j;
    } else if (msg.role === 'tool') {
      // Standalone tool without preceding assistant (edge case)
      const content: Array<JnlTextContent | JnlToolCall> = [
        {
          type: 'tool_use',
          id: msg.toolCallId ?? generateHexId(),
          name: msg.toolName ?? 'unknown',
          input: msg.toolInput ?? {},
        },
      ];

      const assistId = generateHexId();
      const assistEntry: JnlMessageEntry = {
        type: 'message',
        id: assistId,
        parentId: prevId,
        timestamp: new Date(msg.timestamp).toISOString(),
        message: { role: 'assistant', content },
      };
      entries.push(assistEntry);
      prevId = assistId;

      if (msg.output !== undefined) {
        const trId = generateHexId();
        const trEntry: JnlMessageEntry = {
          type: 'message',
          id: trId,
          parentId: prevId,
          timestamp: new Date(msg.timestamp).toISOString(),
          message: {
            role: 'toolResult',
            toolCallId: msg.toolCallId ?? '',
            toolName: msg.toolName ?? 'unknown',
            content: [{ type: 'text', text: msg.output }],
            isError: msg.isError,
          },
        };
        entries.push(trEntry);
        prevId = trId;
      }

      i++;
    } else {
      i++;
    }
  }

  // Append session_info entry
  const infoId = generateHexId();
  const infoEntry: JnlSessionInfoEntry = {
    type: 'session_info',
    id: infoId,
    parentId: prevId,
    timestamp: new Date(meta.updatedAt).toISOString(),
    name: meta.title,
    officer: {
      cost: meta.cost,
      model: meta.model,
      groupSlug: meta.groupSlug ?? null,
      messageCount: meta.messageCount,
      createdAt: meta.createdAt,
      updatedAt: meta.updatedAt,
      context: meta.context,
      contextId: meta.contextId,
    },
  };
  entries.push(infoEntry);

  return entries;
}

type ParsedSession = {
  messages: Message[];
  sessionInfo: JnlSessionInfoEntry | null;
};

export function jnlEntriesToMessages(entries: JnlEntry[]): ParsedSession {
  const messages: Message[] = [];
  let sessionInfo: JnlSessionInfoEntry | null = null;

  for (const entry of entries) {
    if (entry.type === 'session_info') {
      sessionInfo = entry as JnlSessionInfoEntry;
      continue;
    }

    if (entry.type !== 'message') continue;

    const msgEntry = entry as JnlMessageEntry;
    const ts = new Date(entry.timestamp).getTime();

    if (msgEntry.message.role === 'user') {
      const rawContent = msgEntry.message.content;
      const text =
        typeof rawContent === 'string'
          ? rawContent
          : (rawContent as Array<JnlTextContent>).map((c) => c.text).join('\n');
      messages.push({
        id: entry.id,
        timestamp: ts,
        role: 'user',
        text,
      });
    } else if (msgEntry.message.role === 'assistant') {
      const contentBlocks = msgEntry.message.content as Array<JnlTextContent | JnlToolCall>;
      let text = '';
      const toolCalls: JnlToolCall[] = [];

      for (const block of contentBlocks) {
        if (block.type === 'text') {
          text += (text ? '\n' : '') + block.text;
        } else if (block.type === 'tool_use') {
          toolCalls.push(block);
        }
      }

      if (text) {
        messages.push({
          id: entry.id,
          timestamp: ts,
          role: 'assistant',
          text,
        });
      }

      // Create tool messages from tool_use blocks
      for (const tc of toolCalls) {
        messages.push({
          id: randomUUID(),
          timestamp: ts,
          role: 'tool',
          toolCallId: tc.id,
          toolName: tc.name,
          toolInput: tc.input,
        });
      }
    } else if (msgEntry.message.role === 'toolResult') {
      const trMsg = msgEntry.message as {
        role: 'toolResult';
        toolCallId: string;
        toolName: string;
        content: Array<JnlTextContent>;
        isError?: boolean;
      };

      const outputText = trMsg.content.map((c) => c.text).join('\n');

      // Find matching tool message and update it with output
      for (let k = messages.length - 1; k >= 0; k--) {
        const m = messages[k]!;
        if (m.role === 'tool' && m.toolCallId === trMsg.toolCallId) {
          m.output = outputText;
          m.isError = trMsg.isError;
          break;
        }
      }
    }
  }

  return { messages, sessionInfo };
}

// ── Helper: build SessionMeta from index entry ─────────────────────────

function indexEntryToMeta(sessionId: string, entry: SessionIndexEntry): SessionMeta {
  return {
    id: sessionId,
    title: entry.title,
    model: entry.model,
    cwd: entry.cwd,
    createdAt: entry.createdAt,
    updatedAt: entry.updatedAt,
    messageCount: entry.messageCount,
    cost: entry.cost,
    groupSlug: entry.groupSlug ?? null,
    context: entry.context,
    contextId: entry.contextId,
  };
}

function metaToIndexEntry(meta: SessionMeta, relFile: string): SessionIndexEntry {
  return {
    file: relFile,
    title: meta.title,
    model: meta.model,
    cwd: meta.cwd,
    createdAt: meta.createdAt,
    updatedAt: meta.updatedAt,
    messageCount: meta.messageCount,
    cost: meta.cost,
    groupSlug: meta.groupSlug ?? null,
    context: meta.context,
    contextId: meta.contextId,
  };
}

// ── Path resolution ─────────────────────────────────────────────────────

export async function getSessionFilePath(baseCwd: string, sessionId: string): Promise<string | null> {
  const index = await loadIndex(baseCwd);
  const entry = index[sessionId];
  if (!entry) return null;
  return path.join(getSessionsDir(baseCwd), entry.file);
}

// ── Session CRUD ───────────────────────────────────────────────────────

export async function saveSession(
  baseCwd: string,
  sessionId: string,
  meta: SessionMeta,
  messages: Message[],
): Promise<void> {
  const index = await loadIndex(baseCwd);

  // Reuse existing file path or create new one
  const existing = index[sessionId];
  const relFile = existing?.file ?? buildRelativePath(meta.cwd, meta.createdAt, sessionId);

  const absFile = path.join(getSessionsDir(baseCwd), relFile);
  await fs.mkdir(path.dirname(absFile), { recursive: true });

  const header: JnlSessionHeader = {
    type: 'session',
    version: 3,
    id: sessionId,
    timestamp: new Date(meta.createdAt).toISOString(),
    cwd: meta.cwd,
  };

  const entries = messagesToJnlEntries(messages, meta);
  const content = serializeJnlFile(header, entries);
  await fs.writeFile(absFile, content);

  // Update index
  index[sessionId] = metaToIndexEntry(meta, relFile);
  await saveIndex(baseCwd, index);
}

export async function loadSession(
  baseCwd: string,
  sessionId: string,
  _groupSlug?: string | null,
): Promise<{ meta: SessionMeta; messages: Message[] }> {
  const index = await loadIndex(baseCwd);
  const entry = index[sessionId];

  if (!entry) {
    throw new Error(`Session not found: ${sessionId}`);
  }

  const absFile = path.join(getSessionsDir(baseCwd), entry.file);
  const raw = await fs.readFile(absFile, 'utf-8');
  const { entries } = parseJnlFile(raw);
  const { messages, sessionInfo } = jnlEntriesToMessages(entries);

  // Reconstruct meta from index entry (authoritative) enriched by session_info
  const meta: SessionMeta = indexEntryToMeta(sessionId, entry);

  // If session_info has officer data, prefer those for fields that may differ
  if (sessionInfo?.officer) {
    meta.cost = sessionInfo.officer.cost;
    meta.messageCount = sessionInfo.officer.messageCount;
  }
  if (sessionInfo?.name) {
    meta.title = sessionInfo.name;
  }

  return { meta, messages };
}

export async function sessionExists(
  baseCwd: string,
  sessionId: string,
  _groupSlug?: string | null,
): Promise<boolean> {
  const index = await loadIndex(baseCwd);
  return sessionId in index;
}

export async function updateSessionMeta(
  baseCwd: string,
  sessionId: string,
  updates: Partial<SessionMeta>,
  _groupSlug?: string | null,
): Promise<SessionMeta> {
  const { meta, messages } = await loadSession(baseCwd, sessionId);

  const updatedMeta: SessionMeta = {
    ...meta,
    ...updates,
    updatedAt: Date.now(),
  };

  await saveSession(baseCwd, sessionId, updatedMeta, messages);
  return updatedMeta;
}

export async function deleteSession(
  baseCwd: string,
  sessionId: string,
  _groupSlug?: string | null,
): Promise<void> {
  const index = await loadIndex(baseCwd);
  const entry = index[sessionId];

  if (entry) {
    const absFile = path.join(getSessionsDir(baseCwd), entry.file);
    await fs.rm(absFile, { force: true });

    // Clean up empty cwd directory
    try {
      const cwdDir = path.dirname(absFile);
      const remaining = await fs.readdir(cwdDir);
      if (remaining.length === 0) {
        await fs.rmdir(cwdDir);
      }
    } catch {
      // Ignore cleanup errors
    }
  }

  delete index[sessionId];
  await saveIndex(baseCwd, index);
}

type SessionFilter = {
  context?: string;
  contextId?: string;
};

export async function listUserSessions(baseCwd: string, filter?: SessionFilter): Promise<SessionMeta[]> {
  let index = await loadIndex(baseCwd);

  if (Object.keys(index).length === 0) {
    index = await rebuildIndex(baseCwd);
  }

  let sessions: SessionMeta[] = Object.entries(index).map(([id, entry]) => indexEntryToMeta(id, entry));

  if (filter?.context) {
    if (filter.context === 'chat') {
      // 'chat' matches sessions with no context or context='chat'
      sessions = sessions.filter((s) => !s.context || s.context === 'chat');
    } else {
      sessions = sessions.filter((s) => s.context === filter.context && s.contextId === filter.contextId);
    }
  }

  sessions.sort((a, b) => b.updatedAt - a.updatedAt);
  return sessions;
}

export async function searchSessions(
  baseCwd: string,
  query: string,
): Promise<Array<SessionMeta & { preview?: string; relevance?: number }>> {
  const index = await loadIndex(baseCwd);
  const lowerQuery = query.toLowerCase();
  const results: Array<SessionMeta & { preview?: string; relevance?: number }> = [];

  for (const [sessionId, entry] of Object.entries(index)) {
    let relevance = 0;
    let preview = '';

    // Check title (from index — fast)
    if (entry.title.toLowerCase().includes(lowerQuery)) {
      relevance += 1.0;
      preview = entry.title;
    }

    // Check group membership — boost relevance if group matches
    if (entry.groupSlug) {
      try {
        const group = await loadGroup(baseCwd, entry.groupSlug);
        if (group.name.toLowerCase().includes(lowerQuery)) {
          relevance += 2.0;
        }
        if (group.description?.toLowerCase().includes(lowerQuery)) {
          relevance += 1.5;
        }
      } catch {
        // Group file missing — skip boost
      }
    }

    // Lazy content search — only read JSONL if title didn't match
    if (relevance === 0 || !preview) {
      try {
        const absFile = path.join(getSessionsDir(baseCwd), entry.file);
        const raw = await fs.readFile(absFile, 'utf-8');
        const { entries } = parseJnlFile(raw);
        const { messages } = jnlEntriesToMessages(entries);

        for (const msg of messages) {
          if (msg.text && msg.text.toLowerCase().includes(lowerQuery)) {
            relevance += 0.5;
            if (!preview) {
              const idx = msg.text.toLowerCase().indexOf(lowerQuery);
              const start = Math.max(0, idx - 50);
              const end = Math.min(msg.text.length, idx + query.length + 50);
              preview = '...' + msg.text.slice(start, end) + '...';
            }
          }
        }
      } catch {
        // File unreadable — skip
      }
    }

    if (relevance > 0) {
      const meta = indexEntryToMeta(sessionId, entry);
      results.push({ ...meta, preview, relevance });
    }
  }

  results.sort((a, b) => (b.relevance ?? 0) - (a.relevance ?? 0));
  return results;
}

// ── Group management ───────────────────────────────────────────────────

export async function saveGroup(baseCwd: string, groupMeta: GroupMeta): Promise<void> {
  const groupsDir = getGroupsDir(baseCwd);
  await fs.mkdir(groupsDir, { recursive: true });

  const groupPath = getGroupPath(baseCwd, groupMeta.slug);
  await fs.writeFile(groupPath, JSON.stringify(groupMeta, null, 2));
}

export async function loadGroup(baseCwd: string, groupSlug: string): Promise<GroupMeta> {
  const groupPath = getGroupPath(baseCwd, groupSlug);
  const content = await fs.readFile(groupPath, 'utf-8');
  return JSON.parse(content) as GroupMeta;
}

export async function groupExists(baseCwd: string, groupSlug: string): Promise<boolean> {
  try {
    const groupPath = getGroupPath(baseCwd, groupSlug);
    await fs.access(groupPath);
    return true;
  } catch {
    return false;
  }
}

export async function listGroups(baseCwd: string): Promise<GroupMeta[]> {
  const groupsDir = getGroupsDir(baseCwd);

  try {
    await fs.access(groupsDir);
  } catch {
    return [];
  }

  const files = await fs.readdir(groupsDir);
  const groups: GroupMeta[] = [];

  for (const file of files) {
    if (!file.endsWith('.json')) continue;

    try {
      const filePath = path.join(groupsDir, file);
      const content = await fs.readFile(filePath, 'utf-8');
      groups.push(JSON.parse(content) as GroupMeta);
    } catch {
      continue;
    }
  }

  groups.sort((a, b) => b.updatedAt - a.updatedAt);
  return groups;
}

export async function updateGroupMeta(
  baseCwd: string,
  groupSlug: string,
  updates: Partial<GroupMeta>,
): Promise<GroupMeta> {
  const groupMeta = await loadGroup(baseCwd, groupSlug);

  const updated: GroupMeta = {
    ...groupMeta,
    ...updates,
    slug: groupMeta.slug,
    updatedAt: Date.now(),
  };

  await saveGroup(baseCwd, updated);
  return updated;
}

export async function deleteGroup(baseCwd: string, groupSlug: string): Promise<void> {
  const index = await loadIndex(baseCwd);

  // Remove groupSlug from all sessions in this group
  let changed = false;
  for (const entry of Object.values(index)) {
    if (entry.groupSlug === groupSlug) {
      entry.groupSlug = null;
      changed = true;
    }
  }
  if (changed) {
    await saveIndex(baseCwd, index);
  }

  // Delete group file
  const groupPath = getGroupPath(baseCwd, groupSlug);
  await fs.rm(groupPath, { force: true });
}

export async function moveSession(
  baseCwd: string,
  sessionId: string,
  fromGroupSlug: string | null,
  toGroupSlug: string | null,
): Promise<SessionMeta> {
  const index = await loadIndex(baseCwd);
  const entry = index[sessionId];
  if (!entry) {
    throw new Error(`Session not found: ${sessionId}`);
  }

  entry.groupSlug = toGroupSlug;
  entry.updatedAt = Date.now();
  await saveIndex(baseCwd, index);

  // Update group session counts
  if (fromGroupSlug) {
    try {
      const fromGroup = await loadGroup(baseCwd, fromGroupSlug);
      fromGroup.sessionCount = Math.max(0, fromGroup.sessionCount - 1);
      fromGroup.updatedAt = Date.now();
      await saveGroup(baseCwd, fromGroup);
    } catch {
      // Group might not exist
    }
  }

  if (toGroupSlug) {
    try {
      const toGroup = await loadGroup(baseCwd, toGroupSlug);
      toGroup.sessionCount += 1;
      toGroup.updatedAt = Date.now();
      await saveGroup(baseCwd, toGroup);
    } catch {
      // Group might not exist
    }
  }

  return indexEntryToMeta(sessionId, entry);
}

// ── Index recovery ─────────────────────────────────────────────────────

export async function rebuildIndex(baseCwd: string): Promise<SessionIndex> {
  const sessionsDir = getSessionsDir(baseCwd);
  const index: SessionIndex = {};

  try {
    await fs.access(sessionsDir);
  } catch {
    return index;
  }

  const cwdDirs = await fs.readdir(sessionsDir);

  for (const dir of cwdDirs) {
    if (dir === OFFICER_DIR) continue;

    const dirPath = path.join(sessionsDir, dir);
    const stat = await fs.stat(dirPath);
    if (!stat.isDirectory()) continue;

    const files = await fs.readdir(dirPath);

    for (const file of files) {
      if (!file.endsWith('.jsonl')) continue;

      try {
        const filePath = path.join(dirPath, file);
        const raw = await fs.readFile(filePath, 'utf-8');
        const { header, entries } = parseJnlFile(raw);

        const relFile = path.join(dir, file);
        let title = '';
        let cost: MessageCost = { inputTokens: 0, outputTokens: 0, totalUSD: 0 };
        let model = '';
        let messageCount = 0;
        let createdAt = new Date(header.timestamp).getTime();
        let updatedAt = createdAt;
        let groupSlug: string | null = null;
        let context: string | undefined;
        let contextId: string | undefined;

        // Count message entries and find session_info
        for (const entry of entries) {
          if (entry.type === 'message') {
            messageCount++;
          } else if (entry.type === 'session_info') {
            const info = entry as JnlSessionInfoEntry;
            title = info.name;
            if (info.officer) {
              cost = info.officer.cost;
              model = info.officer.model;
              messageCount = info.officer.messageCount;
              createdAt = info.officer.createdAt;
              updatedAt = info.officer.updatedAt;
              groupSlug = info.officer.groupSlug ?? null;
              context = info.officer.context;
              contextId = info.officer.contextId;
            }
          }
        }

        index[header.id] = {
          file: relFile,
          title,
          model,
          cwd: header.cwd,
          createdAt,
          updatedAt,
          messageCount,
          cost,
          groupSlug,
          context,
          contextId,
        };
      } catch {
        continue;
      }
    }
  }

  await saveIndex(baseCwd, index);
  return index;
}