package app

import (
	"encoding/json"
	"fmt"
	"regexp"
	"strings"
	"unicode/utf8"
)

var promptVariablePattern = regexp.MustCompile(`\{\{\s*([a-zA-Z0-9_]+)\s*\}\}`)

func buildGenerationPrompt(templateName string, promptTemplate *string, params map[string]interface{}) string {
	basePrompt := strings.TrimSpace(renderPromptTemplate(promptTemplate, params))
	if basePrompt == "" {
		basePrompt = fmt.Sprintf("Write a complete article in markdown for the template %q.", templateName)
	}

	var sections []string
	sections = append(sections, basePrompt)

	contextBlock := buildPromptContext(params)
	if contextBlock != "" {
		sections = append(sections, "Request context:\n"+contextBlock)
	}

	sections = append(sections, strings.Join([]string{
		"Output requirements:",
		"- Return only article markdown, no surrounding explanation.",
		"- Use the provided title when available.",
		"- Follow the provided outline sections and key points when available.",
		"- Keep structure clear with headings, short paragraphs, and concrete details.",
	}, "\n"))

	return strings.Join(sections, "\n\n")
}

func renderPromptTemplate(promptTemplate *string, params map[string]interface{}) string {
	if promptTemplate == nil {
		return ""
	}

	return promptVariablePattern.ReplaceAllStringFunc(*promptTemplate, func(match string) string {
		submatches := promptVariablePattern.FindStringSubmatch(match)
		if len(submatches) != 2 {
			return match
		}

		value, ok := params[submatches[1]]
		if !ok {
			return ""
		}
		return formatPromptValue(value)
	})
}

func buildPromptContext(params map[string]interface{}) string {
	if len(params) == 0 {
		return ""
	}

	orderedKeys := []string{
		"locale",
		"title",
		"topic",
		"product_name",
		"subject",
		"brand_name",
		"brand",
		"category",
		"count",
		"depth",
		"outline_sections",
		"key_points",
		"keywords",
		"competitors",
	}

	used := make(map[string]struct{}, len(params))
	lines := make([]string, 0, len(params))

	appendLine := func(key string, value interface{}) {
		if value == nil {
			return
		}
		formatted := strings.TrimSpace(formatPromptValue(value))
		if formatted == "" {
			return
		}
		lines = append(lines, fmt.Sprintf("- %s: %s", key, formatted))
		used[key] = struct{}{}
	}

	for _, key := range orderedKeys {
		appendLine(key, params[key])
	}

	for key, value := range params {
		if _, ok := used[key]; ok {
			continue
		}
		appendLine(key, value)
	}

	return strings.Join(lines, "\n")
}

func formatPromptValue(value interface{}) string {
	switch v := value.(type) {
	case nil:
		return ""
	case string:
		return strings.TrimSpace(v)
	case []string:
		return strings.Join(v, ", ")
	case []interface{}:
		parts := make([]string, 0, len(v))
		for _, item := range v {
			formatted := strings.TrimSpace(formatPromptValue(item))
			if formatted != "" {
				parts = append(parts, formatted)
			}
		}
		return strings.Join(parts, ", ")
	default:
		bytes, err := json.Marshal(v)
		if err != nil {
			return fmt.Sprint(v)
		}
		return string(bytes)
	}
}

func resolveArticleTitle(params map[string]interface{}, markdown string) string {
	if title := strings.TrimSpace(stringValue(params["title"])); title != "" {
		return title
	}
	if topic := strings.TrimSpace(stringValue(params["topic"])); topic != "" {
		return topic
	}
	if product := strings.TrimSpace(stringValue(params["product_name"])); product != "" {
		return product + " Review"
	}
	if subject := strings.TrimSpace(stringValue(params["subject"])); subject != "" {
		return subject + " Report"
	}

	for _, line := range strings.Split(markdown, "\n") {
		line = strings.TrimSpace(line)
		if strings.HasPrefix(line, "#") {
			return strings.TrimSpace(strings.TrimLeft(line, "#"))
		}
	}
	return "Generated Article"
}

func estimateWordCount(markdown string) int {
	trimmed := strings.TrimSpace(markdown)
	if trimmed == "" {
		return 0
	}

	words := len(strings.Fields(trimmed))
	if words > 0 {
		return words
	}

	return utf8.RuneCountInString(trimmed)
}

func stringValue(value interface{}) string {
	if value == nil {
		return ""
	}
	text, ok := value.(string)
	if !ok {
		return ""
	}
	return text
}