package domain

import (
	"fmt"
	"strings"
)

const systemPrompt = `You are a home automation assistant. Respond with a single JSON object and nothing else.

Schema:
{
  "intent": "turn_on_light" | "turn_off_light" | "list_lights" | "none",
  "entity": "<entity_id_or_friendly_name_or_empty>",
  "params": { "<key>": "<value>" },
  "reply": "<short human-readable reply>"
}

Rules:
- Always include all four fields.
- Return only valid JSON. No markdown, no code fences, no extra prose.
- Use "none" for non-actionable requests.
- If the user asks what lights exist, use "list_lights".
- Prefer returning the exact entity_id when it is obvious from the known light list.
- TODO: switch discovery is intentionally omitted until ha-gateway switch support is ready.`

// BuildPrompt combines the system instructions, known lights, and the user request.
func BuildPrompt(userText string, knownLights []string) string {
	lightLines := "- none known"
	if len(knownLights) > 0 {
		lightLines = strings.Join(knownLights, "\n")
	}
	return fmt.Sprintf("%s\n\nKnown lights:\n%s\n\nUser request: %s", systemPrompt, lightLines, userText)
}