// Copyright (c) 2026, Pim van Pelt <pim@ipng.ch>

package main

import (
	"context"
	"errors"
	"fmt"
	"io"

	"github.com/chzyer/readline"

	"git.ipng.ch/ipng/vpp-maglev/internal/grpcapi"
)

// errQuit is a sentinel returned by runQuit to exit the REPL.
var errQuit = errors.New("quit")

// runShell runs the interactive REPL until the user types quit/exit or EOF.
func runShell(ctx context.Context, client grpcapi.MaglevClient) error {
	root := buildTree()

	comp := &Completer{root: root, client: client}
	ql := &questionListener{root: root, client: client}

	cfg := &readline.Config{
		Prompt:          "maglev> ",
		AutoComplete:    comp,
		InterruptPrompt: "^C",
		EOFPrompt:       "exit",
		Listener:        ql,
	}
	rl, err := readline.NewEx(cfg)
	if err != nil {
		return fmt.Errorf("readline init: %w", err)
	}
	ql.rl = rl
	defer rl.Close()

	for {
		line, err := rl.Readline()
		if err == readline.ErrInterrupt {
			continue
		}
		if err == io.EOF {
			return nil
		}
		if err != nil {
			return err
		}

		tokens := splitTokens(line)
		if len(tokens) == 0 {
			continue
		}

		if err := dispatch(ctx, root, client, tokens); err != nil {
			if errors.Is(err, errQuit) {
				return nil
			}
			fmt.Fprintf(rl.Stderr(), "error: %v\n", err)
		}
	}
}

// dispatch walks the tree and executes the matched command.
func dispatch(ctx context.Context, root *Node, client grpcapi.MaglevClient, tokens []string) error {
	node, args := Walk(root, tokens)

	if node.Run == nil {
		showHelp(root, tokens)
		return nil
	}

	return node.Run(ctx, client, args)
}

// showHelp prints available completions for the given token path.
func showHelp(root *Node, tokens []string) {
	node, _ := Walk(root, tokens)

	candidates := filterFixedChildren(node.Children, "")
	if len(candidates) == 0 {
		fmt.Println("  <no completions>")
		return
	}
	for _, c := range candidates {
		if c.Help != "" {
			fmt.Printf("  %-20s  %s\n", c.Word, c.Help)
		} else {
			fmt.Printf("  %s\n", c.Word)
		}
	}
}