package app

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

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

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("你是一名专业内容编辑，请基于已提供的信息，为模板「%s」写出一篇完整的 Markdown 文章。", templateName)
	}

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

	contextBlock := buildPromptContext(params)
	if contextBlock != "" {
		sections = append(sections, "当前上下文:\n"+contextBlock)
	}

	sections = append(sections, strings.Join([]string{
		"写作总要求:",
		"- 仅返回文章 Markdown 正文，不要附带额外说明、提示语或代码块。",
		"- 输出语言与 locale 一致：zh-CN 使用简体中文，en-US 使用自然、专业的英语。",
		"- 如提供了 title，使用该标题作为文章主标题，并围绕它展开，不要另起一个无关标题。",
		"- 如提供了 article_outline，一级节点是正文的最终小节标题，必须按顺序展开；二级及更深节点仅作为该小节的行文思路、论证顺序或信息要点，不要机械写成额外标题。",
		"- 除主标题和一级小节标题外，默认不要把大纲子节点直接写成 Markdown 标题；子节点内容应自然融入段落、列表或过渡句中。",
		"- 如提供了 key_points，正文中必须覆盖这些重点，不要遗漏。",
		"- 每个核心段落都要有明确判断、原因解释、适用场景或对比维度，避免空话、套话和重复表述。",
		"- 信息不足时，不要编造具体事实、价格、数据、测试结果、用户评价或机构结论；可以用稳妥表述说明判断边界。",
		"- 保持客观、克制、非广告化，不使用夸张宣传语，如“顶级”“颠覆性”“完美”等。",
		"- 使用清晰的小节标题和短段落；仅在确实有助于理解时使用列表。",
		"- 结尾应给出清晰结论、适合对象、不适合对象，或下一步建议，帮助读者完成判断。",
	}, "\n"))

	if lengthGuidance := buildGenerationLengthGuidance(params); lengthGuidance != "" {
		sections = append(sections, "篇幅要求:\n"+lengthGuidance)
	}

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

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 strings.Join([]string{
			fmt.Sprintf("- 建议全文控制在 %d-%d English words，优先信息密度，不要为了拉长篇幅重复表达。", minWords, maxWords),
			"- Intro and conclusion should stay concise. Most top-level sections only need 1-3 tight paragraphs; expand only the most important sections.",
			"- If one paragraph can make the point clearly, do not split it into multiple repetitive paragraphs.",
		}, "\n")
	}

	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 strings.Join([]string{
		fmt.Sprintf("- 建议全文控制在 %d-%d 字左右，优先信息密度，不要为了凑字数重复表达。", minChars, maxChars),
		"- 引言和结论保持简洁，大多数一级章节写 1-3 个自然段即可；只有最关键的章节需要更充分展开。",
		"- 能用一段说清的内容，不要拆成多段同义反复；主体部分重点写判断、原因、场景和建议。",
	}, "\n")
}

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
		}
		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", 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 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
}