package recipe

import (
	"bytes"
	"fmt"
	"os"
	"regexp"
	"strings"
	"text/template"

	"gopkg.in/yaml.v3"
)

var (
	stepRe = regexp.MustCompile(`(?m)^### Step (\d+): (.+)$`)
	subRe  = regexp.MustCompile(`(?m)^(\*\*(?:Objective|Instructions|Expected output):\*\*)\s*(.+?)(?:\n\n|\n###|\z)`)
)

func Load(path string, userParams map[string]any) (*Recipe, error) {
	b, err := os.ReadFile(path)
	if err != nil {
		return nil, err
	}

	parts := bytes.SplitN(b, []byte("---"), 3)
	if len(parts) < 3 {
		return nil, fmt.Errorf("missing YAML frontmatter")
	}

	var r Recipe
	if err := yaml.Unmarshal(parts[1], &r); err != nil {
		return nil, fmt.Errorf("yaml parse: %w", err)
	}

	// Apply defaults
	if r.Parameters == nil {
		r.Parameters = make(map[string]Parameter)
	}
	params := make(map[string]any)
	for name, p := range r.Parameters {
		if v, ok := userParams[name]; ok {
			params[name] = v
		} else if p.Default != nil {
			params[name] = p.Default
		}
	}

	// Render templates
	tpl, err := template.New("recipe").Parse(string(parts[2]))
	if err != nil {
		return nil, err
	}
	var rendered bytes.Buffer
	if err := tpl.Execute(&rendered, params); err != nil {
		return nil, err
	}
	body := rendered.String()

	// Extract Overview
	if idx := strings.Index(body, "## Execution Steps"); idx != -1 {
		r.Overview = strings.TrimSpace(body[:idx])
	}

	// Extract steps — split-based to guarantee no duplicates
	matches := stepRe.FindAllStringSubmatch(body, -1)
	for i, m := range matches {
		stepNum := i + 1
		title := m[2]

		start := strings.Index(body, m[0])
		end := len(body)
		if i+1 < len(matches) {
			nextStart := strings.Index(body[start:], matches[i+1][0])
			end = start + nextStart
		}

		section := body[start:end]

		step := Step{Number: stepNum, Title: title}
		for _, sub := range subRe.FindAllStringSubmatch(section, -1) {
			switch sub[1] {
			case "**Objective:**":
				step.Objective = strings.TrimSpace(sub[2])
			case "**Instructions:**":
				step.Instructions = strings.TrimSpace(sub[2])
			case "**Expected output:**":
				step.Expected = strings.TrimSpace(sub[2])
			}
		}
		r.Steps = append(r.Steps, step)
	}

	// Final summary = everything after the last step
	if len(matches) > 0 {
		lastMatch := matches[len(matches)-1][0]
		lastIdx := strings.LastIndex(body, lastMatch)
		r.FinalSummaryPrompt = strings.TrimSpace(body[lastIdx+len(lastMatch):])
	}

	return &r, nil
}