package app

import (
	"encoding/json"
	"fmt"
	"regexp"
	"strings"

	"github.com/geo-platform/tenant-api/internal/shared/contentstats"
	"github.com/geo-platform/tenant-api/internal/tenant/prompts"
)

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

func buildGenerationPrompt(
	templateKey, templateName string,
	promptTemplate *string,
	params map[string]interface{},
	knowledgePrompt string,
) string {
	basePrompt := strings.TrimSpace(renderPromptTemplate(promptTemplate, params))
	if basePrompt == "" {
		basePrompt = prompts.DefaultGenerationBasePrompt(templateName)
	}

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

	contextBlock := buildPromptContext(params)
	if contextBlock != "" {
		sections = append(sections, prompts.PromptContextSection(contextBlock))
	}

	if strings.TrimSpace(knowledgePrompt) != "" {
		sections = append(sections, knowledgePrompt)
	}

	sections = append(sections, prompts.GenerationWritingRequirementsSection())

	if templateRules := buildTemplateSpecificWritingRules(templateKey, params); templateRules != "" {
		sections = append(sections, prompts.GenerationTemplateSpecificRulesHeading()+"\n"+templateRules)
	}

	if lengthGuidance := buildGenerationLengthGuidance(params); lengthGuidance != "" {
		sections = append(sections, prompts.GenerationLengthGuidanceHeading()+"\n"+lengthGuidance)
	}

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

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

	parts := make([]string, 0, 8)
	appendValue := func(value string) {
		value = strings.TrimSpace(value)
		if value == "" {
			return
		}
		parts = append(parts, value)
	}

	appendValue(stringValue(params["title"]))
	appendValue(stringValue(params["topic"]))
	appendValue(stringValue(params["product_name"]))
	appendValue(stringValue(params["subject"]))
	appendValue(stringValue(params["brand_name"]))
	appendValue(stringValue(params["primary_keyword"]))
	appendValue(stringValue(params["key_points"]))
	appendValue(stringValue(params["review_intro_hook"]))

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

func buildTemplateSpecificWritingRules(templateKey string, params map[string]interface{}) string {
	switch strings.TrimSpace(templateKey) {
	case "top_x_article":
		brandName := strings.TrimSpace(stringValue(params["brand_name"]))
		if brandName == "" {
			return ""
		}
		return prompts.TopXBrandPriorityRules(brandName)
	default:
		return ""
	}
}

func buildGenerationLengthGuidance(params map[string]interface{}) string {
	sectionCount := estimateTopLevelSectionCount(params)
	if sectionCount <= 0 {
		sectionCount = 4
	}

	locale := strings.TrimSpace(stringValue(params["locale"]))
	if locale == "en-US" {
		minWords := 900
		targetWords := 320 + sectionCount*130
		if targetWords > minWords {
			minWords = targetWords
		}
		if minWords > 1600 {
			minWords = 1600
		}
		maxWords := minWords + 400
		if maxWords > 2100 {
			maxWords = 2100
		}
		return prompts.EnglishLengthGuidance(minWords, maxWords)
	}

	minChars := 1100
	targetChars := 320 + sectionCount*180
	if targetChars > minChars {
		minChars = targetChars
	}
	if minChars > 1800 {
		minChars = 1800
	}
	maxChars := minChars + 500
	if maxChars > 2400 {
		maxChars = 2400
	}

	return prompts.ChineseLengthGuidance(minChars, maxChars)
}

func estimateTopLevelSectionCount(params map[string]interface{}) int {
	if params == nil {
		return 0
	}

	switch value := params["article_outline"].(type) {
	case []interface{}:
		if len(value) > 0 {
			return len(value)
		}
	case []map[string]interface{}:
		if len(value) > 0 {
			return len(value)
		}
	}

	switch value := params["outline_sections"].(type) {
	case []interface{}:
		if len(value) > 0 {
			return len(value)
		}
	case []string:
		if len(value) > 0 {
			return len(value)
		}
	}

	return 0
}

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",
		"primary_keyword",
		"brand",
		"category",
		"count",
		"depth",
		"article_outline",
		"outline_sections",
		"key_points",
		"review_intro_hook",
		"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
		}
		switch key {
		case "knowledge_group_ids", "knowledge_groups", "knowledge_context":
			return
		}
		if key == "outline_sections" && hasStructuredOutline(params["article_outline"]) {
			return
		}
		formatted := strings.TrimSpace(formatPromptContextValue(key, value))
		if formatted == "" {
			return
		}
		lines = append(lines, fmt.Sprintf("- %s: %s", promptContextLabel(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 promptContextLabel(key string) string {
	return prompts.ContextLabel(key)
}

func formatPromptContextValue(key string, value interface{}) string {
	switch key {
	case "keywords":
		return formatKeywordList(value, 6)
	case "competitors":
		return formatCompetitorList(value, 6)
	case "outline_sections":
		return formatSectionList(value, 10)
	case "article_outline":
		return formatOutlineValue(value)
	default:
		return formatPromptValue(value)
	}
}

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{}:
		if hasOutlineItems(v) {
			return formatOutlineItems(v, 0)
		}
		if hasNamedItems(v) {
			return formatNamedItems(v, 6)
		}
		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 formatKeywordList(value interface{}, limit int) string {
	items := extractStringList(value, limit)
	return strings.Join(items, ", ")
}

func formatSectionList(value interface{}, limit int) string {
	items := extractStringList(value, limit)
	return strings.Join(items, " > ")
}

func formatCompetitorList(value interface{}, limit int) string {
	switch items := value.(type) {
	case []interface{}:
		names := make([]string, 0, len(items))
		for _, item := range items {
			if data, ok := item.(map[string]interface{}); ok {
				name := strings.TrimSpace(stringValue(data["name"]))
				if name == "" {
					name = strings.TrimSpace(stringValue(data["brand_name"]))
				}
				if name != "" {
					names = append(names, name)
				}
			}
			if len(names) >= limit {
				break
			}
		}
		return strings.Join(names, ", ")
	default:
		return formatPromptValue(value)
	}
}

func formatOutlineValue(value interface{}) string {
	switch items := value.(type) {
	case []interface{}:
		return formatOutlineItems(items, 0)
	default:
		return formatPromptValue(value)
	}
}

func hasStructuredOutline(value interface{}) bool {
	switch items := value.(type) {
	case []interface{}:
		return hasOutlineItems(items)
	default:
		return false
	}
}

func hasOutlineItems(items []interface{}) bool {
	for _, item := range items {
		if data, ok := item.(map[string]interface{}); ok {
			if strings.TrimSpace(stringValue(data["outline"])) != "" {
				return true
			}
		}
	}
	return false
}

func hasNamedItems(items []interface{}) bool {
	for _, item := range items {
		if data, ok := item.(map[string]interface{}); ok {
			if strings.TrimSpace(stringValue(data["name"])) != "" || strings.TrimSpace(stringValue(data["brand_name"])) != "" {
				return true
			}
		}
	}
	return false
}

func formatNamedItems(items []interface{}, limit int) string {
	names := make([]string, 0, len(items))
	for _, item := range items {
		data, ok := item.(map[string]interface{})
		if !ok {
			continue
		}
		name := strings.TrimSpace(stringValue(data["name"]))
		if name == "" {
			name = strings.TrimSpace(stringValue(data["brand_name"]))
		}
		if name == "" {
			continue
		}
		names = append(names, name)
		if len(names) >= limit {
			break
		}
	}
	return strings.Join(names, ", ")
}

func formatOutlineItems(items []interface{}, level int) string {
	lines := make([]string, 0)
	indent := strings.Repeat("  ", level)
	for _, item := range items {
		node, ok := item.(map[string]interface{})
		if !ok {
			continue
		}
		outline := strings.TrimSpace(stringValue(node["outline"]))
		if outline == "" {
			continue
		}
		lines = append(lines, fmt.Sprintf("%s- %s", indent, outline))
		children, ok := node["children"].([]interface{})
		if ok && len(children) > 0 {
			childText := formatOutlineItems(children, level+1)
			if childText != "" {
				lines = append(lines, childText)
			}
		}
	}
	return strings.Join(lines, "\n")
}

func extractStringList(value interface{}, limit int) []string {
	items := make([]string, 0)
	appendItem := func(text string) {
		text = strings.TrimSpace(text)
		if text == "" {
			return
		}
		items = append(items, text)
	}

	switch list := value.(type) {
	case []string:
		for _, item := range list {
			appendItem(item)
			if limit > 0 && len(items) >= limit {
				break
			}
		}
	case []interface{}:
		for _, item := range list {
			appendItem(formatPromptValue(item))
			if limit > 0 && len(items) >= limit {
				break
			}
		}
	}

	return items
}

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 {
	return contentstats.CountWords(markdown)
}

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