package workflow

import (
	"errors"
	"fmt"
	"strings"
	"unicode"
	"unicode/utf8"

	"g.fc.run/misc/byre/internal/api"
)

var ErrInvalid = errors.New("invalid workflow")

const maxNameRunes = 100

func VendorOf(model string) api.AgentSessionVendor {
	if strings.HasPrefix(model, "gpt-") {
		return api.Codex
	}
	return api.Claude
}

func CleanName(name string) (string, error) {
	name = strings.TrimSpace(name)
	problem := nameProblem(name)
	if problem != "" {
		return "", fmt.Errorf("%w: workflow name %s", ErrInvalid, problem)
	}
	return name, nil
}

func nameProblem(name string) string {
	switch {
	case strings.TrimSpace(name) == "":
		return "is empty"
	case strings.TrimSpace(name) != name:
		return fmt.Sprintf("%q has leading or trailing spaces", name)
	case utf8.RuneCountInString(name) > maxNameRunes:
		return fmt.Sprintf("%q is longer than %d characters", name, maxNameRunes)
	case strings.ContainsFunc(name, unicode.IsControl):
		return fmt.Sprintf("%q isn't a single line", name)
	}
	return ""
}

func Validate(def api.WorkflowDefinition) error {
	problems := []string{}
	if len(def.Stages) == 0 {
		problems = append(problems, "it has no stages")
	}

	seen := map[string]bool{}
	for i, s := range def.Stages {
		where := fmt.Sprintf("stage %d (%q)", i+1, s.Name)
		p := nameProblem(s.Name)
		if p != "" {
			problems = append(problems, fmt.Sprintf("%s: name %s", where, p))
		}
		if seen[s.Name] {
			problems = append(problems, fmt.Sprintf("%s: another stage has the same name", where))
		}
		seen[s.Name] = true

		if strings.TrimSpace(s.Model) == "" {
			problems = append(problems, fmt.Sprintf("%s: model is required", where))
		}

		if strings.TrimSpace(s.Prompt) == "" {
			problems = append(problems, fmt.Sprintf("%s: prompt is empty", where))
		}
	}

	if len(problems) > 0 {
		return fmt.Errorf("%w: %s", ErrInvalid, strings.Join(problems, "; "))
	}
	return nil
}