const { getEnv, SERVICES, EPISODIC } = require('@nexusai/shared');

const BASE_URL = getEnv('MEMORY_SERVICE_URL', SERVICES.MEMORY_URL);

//function to get session by external id, returns null if not found, throws error for other issues
async function getSessionByExternalId(externalId) {
    const res = await fetch(`${BASE_URL}/sessions/by-external/${externalId}`);

    if (res.status === 404) return null; // Not found or bad request
    if (!res.ok) throw new Error(`Memory service error: ${res.status} ${res.statusText}`);  // Other errors

    return res.json();
}

// create a new session with an external ID, returns the created session
async function createSession(externalId) {
    const res = await fetch(`${BASE_URL}/sessions`, {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ externalId })
    });
    if (!res.ok) throw new Error(`Failed to create sessions: ${res.status} ${res.statusText}`);
    return res.json();
}

async function getRecentEpisodes(sessionId, limit = EPISODIC.DEFAULT_SESSIONS_LIMIT) {
    const res = await fetch(`${BASE_URL}/sessions/${sessionId}/episodes?limit=${limit}`);
    if (!res.ok) throw new Error(`Failed to fetch episodes: ${res.status} ${res.statusText}`);
    return res.json();
}

async function createEpisode(sessionId, userMessage, aiResponse, tokenCount, projectId=null) {
    const res = await fetch(`${BASE_URL}/episodes`, {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ sessionId, userMessage, aiResponse, tokenCount, projectId })
    });
    if (!res.ok) throw new Error(`Failed to create episode: ${res.status} ${res.statusText}`);
    return res.json();
}

async function getEpisodeById(episodeId) {
    const res = await fetch(`${BASE_URL}/episodes/${episodeId}`);
    if (res.status === 404) return null;
    if (!res.ok) throw new Error(`Failed to fetch episode: ${res.status}`);
    return res.json();
}

async function getSessionHistory(sessionId, limit = EPISODIC.DEFAULT_SESSIONS_LIMIT, offset = EPISODIC.DEFAULT_OFFSET) {
    const res = await fetch(
        `${BASE_URL}/sessions/${sessionId}/episodes?limit=${limit}&offset=${offset}`
    );
    if (res.status === 404 ) return null;
    if (!res.ok) throw new Error(`Failed to fetch history: ${res.status}`);
    return res.json();
}

async function getSessions(limit = EPISODIC.DEFAULT_SESSIONS_LIMIT, offset = EPISODIC.DEFAULT_OFFSET, projectId = null) {
  const url = new URL(`${BASE_URL}/sessions`);
  url.searchParams.set('limit', limit);
  url.searchParams.set('offset', offset);
  if (projectId) url.searchParams.set('projectId', projectId);

  const res = await fetch(url.toString());
  if (!res.ok) throw new Error(`Failed to fetch sessions: ${res.status}`);
  return res.json();
}

async function updateSession(externalId, { name, projectId }) {
    const res = await fetch(`${BASE_URL}/sessions/by-external/${externalId}`, {
        method: 'PATCH',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ name, projectId }),
    });
    if (!res.ok) throw new Error(`Failed to update session: ${res.status}`);
    return res.json();
}

async function deleteSession(externalId) {
    const res = await fetch(`${BASE_URL}/sessions/by-external/${externalId}`, {
        method: 'DELETE',
    });
    if (!res.ok) throw new Error(`Failed to delete session: ${res.status}`);
}

/******** PROJECTS ********* */
async function createProject({ name, description, colour, icon }) {
    const res = await fetch(`${BASE_URL}/projects`, {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ name, description, colour, icon })
    });
    if (!res.ok) throw new Error(`Failed to create project: ${res.status}`);
    return res.json();
}

async function getProjects() {
    const res = await fetch(`${BASE_URL}/projects`);
    if (!res.ok) throw new Error(`Failed to fetch projects: ${res.status}`);
    return res.json();
}

async function updateProject(id, fields = {}) {
    const res = await fetch(`${BASE_URL}/projects/${id}`, {
        method: 'PATCH',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify(fields)
    });
    if (!res.ok) throw new Error(`Failed to update project: ${res.status}`);
    return res.json();
}

async function deleteProject(id) {
    const res = await fetch(`${BASE_URL}/projects/${id}`, { method: 'DELETE' });
    if (!res.ok) throw new Error(`Failed to delete project: ${res.status}`);
}

async function getProjectSessions(projectId) {
  const url = new URL(`${BASE_URL}/sessions`);
  url.searchParams.set('limit', 200);  // generous upper bound
  url.searchParams.set('offset', 0);
  url.searchParams.set('projectId', projectId);

  const res = await fetch(url.toString());
  if (!res.ok) throw new Error(`Failed to fetch project sessions: ${res.status}`);
  return res.json(); // returns array of session objects
}

async function getProject(id) {
  const res = await fetch(`${BASE_URL}/projects/${id}`);
  if (res.status === 404) return null;
  if (!res.ok) throw new Error(`Failed to fetch project: ${res.status}`);
  return res.json();
}

async function getEpisodes({ limit = 50, offset = 0, sessionId, q } = {}) {
  const url = new URL(`${BASE_URL}/episodes`);
  url.searchParams.set('limit', limit);
  url.searchParams.set('offset', offset);
  if (sessionId) url.searchParams.set('sessionId', sessionId);
  if (q) url.searchParams.set('q', q);

  const res = await fetch(url.toString());
  if (!res.ok) throw new Error(`Failed to fetch episodes: ${res.status}`);
  return res.json();
}

async function deleteEpisode(id) {
  const res = await fetch(`${BASE_URL}/episodes/${id}`, { method: 'DELETE' });
  if (!res.ok) throw new Error(`Failed to delete episode: ${res.status}`);
}

async function getSummariesBySession(sessionId) {
    const res = await fetch(`${BASE_URL}/sessions/${sessionId}/summaries`);
    if (!res.ok) throw new Error(`Failed to fetch summaries: ${res.status}`);
    return res.json();
}

async function createSummary({ sessionId, projectId, content, tokenCount, episodeRange }) {
    const res = await fetch(`${BASE_URL}/summaries`, {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ sessionId, projectId, content, tokenCount, episodeRange }),
    });
    if (!res.ok) throw new Error(`Failed to create summary: ${res.status}`);
    return res.json();
}

async function updateSummary(id, { content, tokenCount, episodeRange }) {
    const res = await fetch(`${BASE_URL}/summaries/${id}`, {
        method: 'PATCH',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ content, tokenCount, episodeRange }),
    });
    if (!res.ok) throw new Error(`Failed to update summary: ${res.status}`);
    return res.json();
}

async function getSummariesByProject(projectId) {
    const res = await fetch(`${BASE_URL}/projects/${projectId}/summaries`);
    if (!res.ok) throw new Error(`Failed to fetch summaries: ${res.status}`);
    return res.json();
}

async function generateProjectSummary(projectId) {
    const res = await fetch(`${BASE_URL}/projects/${projectId}/summarize`, {
        method: 'POST',
    });
    if (!res.ok) throw new Error(`Failed to generate project summary: ${res.status}`);
    return res.json();
}

async function getProjectOverviewSummary(projectId) {
    const res = await fetch(`${BASE_URL}/projects/${projectId}/overview`);
    if (!res.ok) throw new Error(`Failed to fetch project overview: ${res.status}`);
    return res.json(); // null if none exists yet
}

async function searchEpisodes(query, { limit = 10, sessionIds = null } = {}) {
    const url = new URL(`${BASE_URL}/episodes/search`);
    url.searchParams.set('q', query);
    url.searchParams.set('limit', limit);
    if (sessionIds?.length) url.searchParams.set('sessionIds', sessionIds.join(','));
    const res = await fetch(url.toString());
    if (!res.ok) throw new Error(`FTS search error: ${res.status}`);
    return res.json();
}

async function getEpisodesByEntities(entityIds) {
    const res = await fetch(`${BASE_URL}/episodes/by-entities`, {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ entityIds }),
    });
    if (!res.ok) throw new Error(`Episodes-by-entities error: ${res.status}`);
    return res.json(); // { episodeIds: [...] }
}

async function getEntityIdsBySession(sessionId){
    const res = await fetch(`${BASE_URL}/sessions/${sessionId}/entity-ids`);

    if (!res.ok) throw new Error(`Entity-ids-by-session error: ${res.status}`);
    const {entityIds} = await res.jaon();
    return entityIds;
}

module.exports = {
    getSessionByExternalId,
    createSession,
    getRecentEpisodes,
    createEpisode,
    getEpisodeById,
    getSessionHistory,
    getSessions,
    updateSession,
    deleteSession,
    createProject,
    getProjects,
    updateProject,
    deleteProject,
    getProjectSessions,
    getProject,
    getEpisodes,
    deleteEpisode,
    getSummariesBySession,
    createSummary,
    updateSummary,
    getSummariesByProject,
    generateProjectSummary,
    getProjectOverviewSummary,
    searchEpisodes,
    getEpisodesByEntities,
    getEntityIdsBySession,
}