// Package session provides polecat session lifecycle management.
package session

import (
	"fmt"
	"os"
	"path/filepath"
	"strings"
)

// Prefix is the common prefix for rig-level Gas Town tmux sessions.
const Prefix = "gt-"

// HQPrefix is the prefix for town-level services (Mayor, Deacon).
const HQPrefix = "hq-"

// MayorSessionName returns the session name for the Mayor agent.
// One mayor per machine - multi-town requires containers/VMs for isolation.
func MayorSessionName() string {
	return HQPrefix + "mayor"
}

// DeaconSessionName returns the session name for the Deacon agent.
// One deacon per machine - multi-town requires containers/VMs for isolation.
func DeaconSessionName() string {
	return HQPrefix + "deacon"
}

// WitnessSessionName returns the session name for a rig's Witness agent.
func WitnessSessionName(rig string) string {
	return fmt.Sprintf("%s%s-witness", Prefix, rig)
}

// RefinerySessionName returns the session name for a rig's Refinery agent.
func RefinerySessionName(rig string) string {
	return fmt.Sprintf("%s%s-refinery", Prefix, rig)
}

// CrewSessionName returns the session name for a crew worker in a rig.
func CrewSessionName(rig, name string) string {
	return fmt.Sprintf("%s%s-crew-%s", Prefix, rig, name)
}

// PolecatSessionName returns the session name for a polecat in a rig.
func PolecatSessionName(rig, name string) string {
	return fmt.Sprintf("%s%s-%s", Prefix, rig, name)
}

// PropulsionNudge generates the GUPP (Gas Town Universal Propulsion Principle) nudge.
// This is sent after the beacon to trigger autonomous work execution.
// The agent receives this as user input, triggering the propulsion principle:
// "If work is on your hook, YOU RUN IT."
func PropulsionNudge() string {
	return "Run `gt hook` to check your hook and begin work."
}

// PropulsionNudgeForRole generates a role-specific GUPP nudge.
// Different roles have different startup flows:
// - polecat/crew: Check hook for slung work
// - witness/refinery: Start patrol cycle
// - deacon: Start heartbeat patrol
// - mayor: Check mail for coordination work
//
// The workDir parameter is used to locate .runtime/session_id for including
// session ID in the message (for Claude Code /resume picker discovery).
func PropulsionNudgeForRole(role, workDir string) string {
	var msg string
	switch role {
	case "polecat", "crew":
		msg = PropulsionNudge()
	case "witness":
		msg = "Run `gt prime` to check patrol status and begin work."
	case "refinery":
		msg = "Run `gt prime` to check MQ status and begin patrol."
	case "deacon":
		msg = "Run `gt prime` to check patrol status and begin heartbeat cycle."
	case "mayor":
		msg = "Run `gt prime` to check mail and begin coordination."
	default:
		msg = PropulsionNudge()
	}

	// Append session ID if available (for /resume picker visibility)
	if sessionID := readSessionID(workDir); sessionID != "" {
		msg = fmt.Sprintf("%s [session:%s]", msg, sessionID)
	}
	return msg
}

// readSessionID reads the session ID from .runtime/session_id if it exists.
// Returns empty string if the file doesn't exist or can't be read.
func readSessionID(workDir string) string {
	if workDir == "" {
		return ""
	}
	sessionPath := filepath.Join(workDir, ".runtime", "session_id")
	data, err := os.ReadFile(sessionPath)
	if err != nil {
		return ""
	}
	return strings.TrimSpace(string(data))
}