// Package message provides pure parsing and formatting for Matrix messages.
package message

import (
	"strings"

	"github.com/enmanuel/agents/pkg/decision"
)

// ParseOptions configures how messages are parsed.
type ParseOptions struct {
	CommandPrefix    string   // e.g. "!"
	BotUserID        string   // for mention detection, e.g. "@bot:server"
	MentionedUserIDs []string // pre-extracted from m.mentions event field (modern Matrix spec)
}

// Parse converts a raw Matrix message body into a structured MessageContext. Pure.
func Parse(body, senderID, roomID string, powerLevel int, isDM bool, opts ParseOptions) decision.MessageContext {
	ctx := decision.MessageContext{
		SenderID:    senderID,
		RoomID:      roomID,
		Content:     body,
		PowerLevel:  powerLevel,
		IsDirectMsg: isDM,
	}

	// Detect mention: check m.mentions list first (modern Matrix spec).
	if opts.BotUserID != "" {
		for _, uid := range opts.MentionedUserIDs {
			if uid == opts.BotUserID {
				ctx.IsMention = true
				break
			}
		}
		// Fallback: check if full user ID appears in the plain text body.
		if !ctx.IsMention && strings.Contains(body, opts.BotUserID) {
			ctx.IsMention = true
		}
	}

	// Parse command
	if opts.CommandPrefix != "" && strings.HasPrefix(body, opts.CommandPrefix) {
		parts := strings.Fields(strings.TrimPrefix(body, opts.CommandPrefix))
		if len(parts) > 0 {
			ctx.Command = strings.ToLower(parts[0])
			ctx.Args = parts[1:]
		}
	}

	return ctx
}