feat: AI client and prompt templates

src/ai/client.ts

@@ -0,0 +1,9 @@
+import OpenAI from 'openai';
+import { config } from '../config';
+
+export function createAiClient(): OpenAI {
+  return new OpenAI({
+    apiKey: config.openrouterApiKey,
+    baseURL: 'https://openrouter.ai/api/v1',
+  });
+}

src/ai/prompts.ts

@@ -0,0 +1,88 @@
+import type { AIContext } from './context';
+import { formatDuration } from '../utils/duration';
+
+function sessionLines(ctx: AIContext): string {
+  if (ctx.recentSessions.length === 0) return 'No sessions recorded yet.';
+  return ctx.recentSessions
+    .map(s => `  ${s.date}: ${formatDuration(s.duration_min)}${s.notes ? ` (${s.notes})` : ''}`)
+    .join('\n');
+}
+
+function scheduleLines(ctx: AIContext): string {
+  if (ctx.upcomingSchedule.length === 0) return 'No upcoming schedule.';
+  return ctx.upcomingSchedule
+    .map(e => `  ${e.date}: ${formatDuration(e.planned_min)} [${e.status}]`)
+    .join('\n');
+}
+
+function skipLines(ctx: AIContext): string {
+  if (ctx.recentSkips.length === 0) return 'None.';
+  return ctx.recentSkips
+    .map(s => `  ${s.date}${s.reason ? `: ${s.reason}` : ''}`)
+    .join('\n');
+}
+
+function systemBase(ctx: AIContext): string {
+  return `You are a supportive personal training coach. You help the user track and improve their anal training practice.
+
+Today: ${ctx.today}
+Training goal: ${ctx.goal}
+Current streak: ${ctx.currentStreak} sessions
+
+Recent sessions (newest first):
+${sessionLines(ctx)}
+
+Upcoming schedule:
+${scheduleLines(ctx)}
+
+Recent skips:
+${skipLines(ctx)}
+
+Be encouraging but honest. Always explain your reasoning. Flag if you think the pace is too fast or too slow.`;
+}
+
+export function progressPrompt(ctx: AIContext): { system: string; user: string } {
+  return {
+    system: systemBase(ctx),
+    user: 'Analyse my recent training history. Give me a summary of my progress, highlight any patterns (positive or negative), and tell me how I\'m tracking toward my goal.',
+  };
+}
+
+export function nextStepPrompt(ctx: AIContext): { system: string; user: string } {
+  return {
+    system: systemBase(ctx),
+    user: 'Based on my history, what should my next training step be? Should I increase duration, maintain, or take a rest? Explain your reasoning.',
+  };
+}
+
+export function reschedulePrompt(ctx: AIContext, note: string | null): { system: string; user: string } {
+  const extra = note ? `\n\nAdditional context from the user: "${note}"` : '';
+  return {
+    system: systemBase(ctx),
+    user: `Generate a training schedule for the next 14 days starting from ${ctx.today}.${extra}
+
+Respond with ONLY a JSON array — no prose, no markdown explanation — in this exact format:
+[
+  { "date": "YYYY-MM-DD", "planned_min": 60, "rationale": "reason" }
+]
+
+Only include days with planned sessions (rest days are omitted). Space sessions appropriately.`,
+  };
+}
+
+export function setupPrompt(
+  currentLevel: string, availability: string, goal: string
+): { system: string; user: string } {
+  return {
+    system: 'You are a supportive personal training coach helping a new user set up their anal training plan. Be warm, practical, and non-judgmental.',
+    user: `New user setup:
+- Current level: ${currentLevel}
+- Typical availability: ${availability}
+- Goal: ${goal}
+
+Generate a 14-day starter schedule. Respond with ONLY a JSON array in this exact format:
+[
+  { "date": "YYYY-MM-DD", "planned_min": 30, "rationale": "Starting gently" }
+]`,
+  };
+}