package httpserver

import (
	"context"
	"database/sql"
	"encoding/json"
	"errors"
	"fmt"
	"html/template"
	"io"
	"io/fs"
	"net/http"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"time"

	"github.com/go-chi/chi/v5"

	"github.com/tim/cairnquire/apps/server/internal/docs"
)

type layoutData struct {
	Title        string
	WebEnabled   bool
	BodyClass    string
	BodyTemplate string
	Data         any
}

type indexData struct {
	Browser browserData
}

type documentData struct {
	Browser     browserData
	Title       string
	Path        string
	Tags        []string
	Hash        string
	HTML        template.HTML
	Breadcrumbs []breadcrumb
}

type documentEditData struct {
	Browser     browserData
	Title       string
	Path        string
	Tags        []string
	Hash        string
	Source      string
	Breadcrumbs []breadcrumb
}

type breadcrumb struct {
	Name string
	URL  string
}

type errorData struct {
	Status  int
	Message string
}

type browserData struct {
	Columns []browserColumn
}

type browserColumn struct {
	Title string
	Items []browserItem
}

type browserItem struct {
	Name     string
	Path     string
	URL      string
	IsFolder bool
	IsIndex  bool
	HasIndex bool
	Active   bool
}

func (s *Server) handleIndex(w http.ResponseWriter, r *http.Request) {
	query := r.URL.Query().Get("q")
	if query != "" {
		s.handleSearchPage(w, r, query)
		return
	}

	items, err := s.documents.ListDocuments(r.Context())
	if err != nil {
		s.renderError(w, r, http.StatusInternalServerError, err.Error())
		return
	}

	activeFolder := strings.Trim(r.URL.Query().Get("folder"), "/")
	s.renderTemplate(w, http.StatusOK, "index.gohtml", layoutData{
		Title:        "Cairnquire",
		WebEnabled:   s.webEnabled,
		BodyClass:    "page-index",
		BodyTemplate: "index_content",
		Data: indexData{
			Browser: buildBrowser(items, activeFolder),
		},
	})
}

func (s *Server) handleSearchPage(w http.ResponseWriter, r *http.Request, query string) {
	ctx, cancel := context.WithTimeout(r.Context(), 5*time.Second)
	defer cancel()

	results, err := s.repository.SearchDocuments(ctx, query)
	if err != nil {
		s.logger.Warn("search failed", "error", err)
	}

	s.renderTemplate(w, http.StatusOK, "search.gohtml", layoutData{
		Title:        "Search: " + query,
		WebEnabled:   s.webEnabled,
		BodyClass:    "page-search",
		BodyTemplate: "search_content",
		Data: struct {
			Query   string
			Results []docs.SearchResult
		}{
			Query:   query,
			Results: results,
		},
	})
}

func (s *Server) handleDocsIndex(w http.ResponseWriter, r *http.Request) {
	s.renderDocumentPage(w, r, "")
}

func (s *Server) handleDocument(w http.ResponseWriter, r *http.Request) {
	pagePath := chi.URLParam(r, "*")
	if isContentAssetPath(pagePath) {
		s.handleContentAsset(w, r, pagePath)
		return
	}
	if editPath, ok := trimEditSuffix(pagePath); ok {
		s.renderDocumentEditor(w, r, editPath)
		return
	}
	s.renderDocumentPage(w, r, pagePath)
}

func (s *Server) handleContentAsset(w http.ResponseWriter, r *http.Request, assetPath string) {
	cleanPath := filepath.Clean(filepath.FromSlash(strings.TrimPrefix(assetPath, "/")))
	if cleanPath == "." || strings.HasPrefix(cleanPath, ".."+string(filepath.Separator)) || filepath.IsAbs(cleanPath) {
		s.renderError(w, r, http.StatusNotFound, "asset not found")
		return
	}

	fullPath := filepath.Join(s.config.Content.SourceDir, cleanPath)
	sourceRoot, err := filepath.Abs(s.config.Content.SourceDir)
	if err != nil {
		s.renderError(w, r, http.StatusInternalServerError, "resolve content root")
		return
	}
	assetAbs, err := filepath.Abs(fullPath)
	if err != nil {
		s.renderError(w, r, http.StatusNotFound, "asset not found")
		return
	}
	relative, err := filepath.Rel(sourceRoot, assetAbs)
	if err != nil || relative == ".." || strings.HasPrefix(relative, ".."+string(filepath.Separator)) {
		s.renderError(w, r, http.StatusNotFound, "asset not found")
		return
	}

	file, err := os.Open(assetAbs)
	if err != nil {
		if errors.Is(err, os.ErrNotExist) {
			s.renderError(w, r, http.StatusNotFound, "asset not found")
			return
		}
		s.renderError(w, r, http.StatusInternalServerError, "read asset")
		return
	}
	defer file.Close()

	info, err := file.Stat()
	if err != nil || info.IsDir() {
		s.renderError(w, r, http.StatusNotFound, "asset not found")
		return
	}

	buffer := make([]byte, 512)
	n, _ := file.Read(buffer)
	if _, err := file.Seek(0, io.SeekStart); err != nil {
		s.renderError(w, r, http.StatusInternalServerError, "read asset")
		return
	}
	contentType := http.DetectContentType(buffer[:n])
	if !isAllowedContentType(contentType) {
		s.renderError(w, r, http.StatusNotFound, "asset not found")
		return
	}

	w.Header().Set("Content-Type", contentType)
	w.Header().Set("Content-Length", fmt.Sprintf("%d", info.Size()))
	http.ServeContent(w, r, info.Name(), info.ModTime(), file)
}

func (s *Server) renderDocumentEditor(w http.ResponseWriter, r *http.Request, pagePath string) {
	page, err := s.documents.LoadSourcePage(r.Context(), pagePath)
	if err != nil {
		if errors.Is(err, sql.ErrNoRows) {
			s.renderError(w, r, http.StatusNotFound, "document not found")
			return
		}
		s.renderError(w, r, http.StatusInternalServerError, err.Error())
		return
	}

	items, err := s.documents.ListDocuments(r.Context())
	if err != nil {
		s.renderError(w, r, http.StatusInternalServerError, err.Error())
		return
	}

	s.renderTemplate(w, http.StatusOK, "document_edit.gohtml", layoutData{
		Title:        "Edit: " + page.Title,
		WebEnabled:   s.webEnabled,
		BodyClass:    "page-document-edit",
		BodyTemplate: "document_edit_content",
		Data: documentEditData{
			Browser:     buildBrowser(items, page.Path),
			Title:       page.Title,
			Path:        page.Path,
			Tags:        page.Tags,
			Hash:        page.Hash,
			Source:      page.Content,
			Breadcrumbs: buildBreadcrumbs(page.Path),
		},
	})
}

func (s *Server) renderDocumentPage(w http.ResponseWriter, r *http.Request, pagePath string) {
	page, err := s.documents.LoadPage(r.Context(), pagePath)
	if err != nil {
		if errors.Is(err, sql.ErrNoRows) {
			s.renderError(w, r, http.StatusNotFound, "document not found")
			return
		}
		s.renderError(w, r, http.StatusInternalServerError, err.Error())
		return
	}

	items, err := s.documents.ListDocuments(r.Context())
	if err != nil {
		s.renderError(w, r, http.StatusInternalServerError, err.Error())
		return
	}

	s.renderTemplate(w, http.StatusOK, "document.gohtml", layoutData{
		Title:        page.Title,
		WebEnabled:   s.webEnabled,
		BodyClass:    "page-document",
		BodyTemplate: "document_content",
		Data: documentData{
			Browser:     buildBrowser(items, page.Path),
			Title:       page.Title,
			Path:        page.Path,
			Tags:        page.Tags,
			Hash:        page.Hash,
			HTML:        template.HTML(page.HTML),
			Breadcrumbs: buildBreadcrumbs(page.Path),
		},
	})
}

func (s *Server) handleHealth(w http.ResponseWriter, r *http.Request) {
	ctx, cancel := context.WithTimeout(r.Context(), 2*time.Second)
	defer cancel()

	dbStatus := "ok"
	if err := s.repository.Ping(ctx); err != nil {
		dbStatus = err.Error()
	}

	contentStatus := "ok"
	if _, err := os.Stat(s.config.Content.StoreDir); err != nil {
		contentStatus = err.Error()
	}

	writeJSON(w, http.StatusOK, map[string]string{
		"status":       "ok",
		"database":     dbStatus,
		"contentStore": contentStatus,
	})
}

func (s *Server) handleServiceWorker(w http.ResponseWriter, r *http.Request) {
	content, err := fs.ReadFile(assets, "static/sw.js")
	if err != nil {
		http.Error(w, "service worker unavailable", http.StatusInternalServerError)
		return
	}

	w.Header().Set("Content-Type", "application/javascript; charset=utf-8")
	w.Header().Set("Cache-Control", "no-cache")
	w.Header().Set("Service-Worker-Allowed", "/")
	w.WriteHeader(http.StatusOK)
	_, _ = w.Write(content)
}

func (s *Server) handleSearch(w http.ResponseWriter, r *http.Request) {
	query := r.URL.Query().Get("q")
	if query == "" {
		writeJSON(w, http.StatusOK, map[string]interface{}{"results": []any{}})
		return
	}

	ctx, cancel := context.WithTimeout(r.Context(), 5*time.Second)
	defer cancel()

	results, err := s.repository.SearchDocuments(ctx, query)
	if err != nil {
		s.logger.Warn("search failed", "error", err)
		writeJSON(w, http.StatusOK, map[string]interface{}{"results": []any{}})
		return
	}

	writeJSON(w, http.StatusOK, map[string]interface{}{"results": results})
}

func (s *Server) handleUpload(w http.ResponseWriter, r *http.Request) {
	if err := r.ParseMultipartForm(32 << 20); err != nil {
		s.renderError(w, r, http.StatusBadRequest, "invalid multipart upload")
		return
	}

	file, header, err := r.FormFile("file")
	if err != nil {
		s.renderError(w, r, http.StatusBadRequest, "file field is required")
		return
	}
	defer file.Close()

	content, err := io.ReadAll(io.LimitReader(file, 32<<20))
	if err != nil {
		s.renderError(w, r, http.StatusInternalServerError, "read upload")
		return
	}

	contentType := http.DetectContentType(content)
	if !isAllowedContentType(contentType) {
		s.renderError(w, r, http.StatusBadRequest, "unsupported content type")
		return
	}

	record, err := s.contentStore.PutBytes(content)
	if err != nil {
		s.renderError(w, r, http.StatusInternalServerError, "store upload")
		return
	}

	if err := s.repository.SaveAttachment(r.Context(), docs.AttachmentRecord{
		Hash:         record.Hash,
		OriginalName: header.Filename,
		ContentType:  contentType,
		SizeBytes:    record.Size,
		CreatedAt:    time.Now().UTC(),
	}); err != nil {
		s.renderError(w, r, http.StatusInternalServerError, "persist upload metadata")
		return
	}

	writeJSONWithStatus(w, http.StatusCreated, map[string]string{
		"hash":          record.Hash,
		"contentType":   contentType,
		"attachmentUrl": "/attachments/" + record.Hash,
	})
}

func (s *Server) handleAttachment(w http.ResponseWriter, r *http.Request) {
	hash := chi.URLParam(r, "hash")
	attachment, err := s.repository.GetAttachment(r.Context(), hash)
	if err != nil {
		if errors.Is(err, sql.ErrNoRows) {
			s.renderError(w, r, http.StatusNotFound, "attachment not found")
			return
		}
		s.renderError(w, r, http.StatusInternalServerError, "lookup attachment")
		return
	}

	content, err := s.contentStore.Read(hash)
	if err != nil {
		s.renderError(w, r, http.StatusInternalServerError, "read attachment")
		return
	}

	w.Header().Set("Content-Type", attachment.ContentType)
	w.Header().Set("Content-Disposition", fmt.Sprintf("inline; filename=%q", sanitizeFilename(attachment.OriginalName)))
	w.Header().Set("Content-Length", fmt.Sprintf("%d", len(content)))
	w.WriteHeader(http.StatusOK)
	_, _ = w.Write(content)
}

func (s *Server) renderTemplate(w http.ResponseWriter, status int, name string, data layoutData) {
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	w.WriteHeader(status)
	if err := s.templates.ExecuteTemplate(w, name, data); err != nil {
		http.Error(w, "template error", http.StatusInternalServerError)
	}
}

func (s *Server) renderError(w http.ResponseWriter, r *http.Request, status int, message string) {
	s.renderTemplate(w, status, "error.gohtml", layoutData{
		Title:        http.StatusText(status),
		WebEnabled:   s.webEnabled,
		BodyClass:    "page-error",
		BodyTemplate: "error_content",
		Data: errorData{
			Status:  status,
			Message: message,
		},
	})
}

func isAllowedContentType(contentType string) bool {
	allowed := []string{
		"image/png",
		"image/jpeg",
		"image/gif",
		"image/webp",
		"application/pdf",
		"text/plain; charset=utf-8",
	}
	for _, candidate := range allowed {
		if strings.EqualFold(candidate, contentType) {
			return true
		}
	}
	return false
}

func sanitizeFilename(name string) string {
	name = filepath.Base(name)
	return strings.ReplaceAll(name, "\"", "")
}

func (s *Server) handleDocuments(w http.ResponseWriter, r *http.Request) {
	records, err := s.documents.ListDocuments(r.Context())
	if err != nil {
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
		return
	}

	results := make([]map[string]any, 0, len(records))
	for _, record := range records {
		results = append(results, map[string]any{
			"path":  record.Path,
			"title": record.Title,
			"hash":  record.CurrentHash,
		})
	}

	writeJSON(w, http.StatusOK, map[string]any{"documents": results})
}

func (s *Server) handleDocumentSave(w http.ResponseWriter, r *http.Request) {
	pagePath := chi.URLParam(r, "*")
	if pagePath == "" {
		writeJSONWithStatus(w, http.StatusBadRequest, map[string]string{"error": "document path is required"})
		return
	}

	var req struct {
		Content  string `json:"content"`
		BaseHash string `json:"baseHash"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeJSONWithStatus(w, http.StatusBadRequest, map[string]string{"error": "invalid request body"})
		return
	}

	page, err := s.documents.SaveSourcePageWithBaseHash(r.Context(), pagePath, req.Content, req.BaseHash)
	if err != nil {
		var conflict *docs.DocumentConflictError
		if errors.As(err, &conflict) {
			writeJSONWithStatus(w, http.StatusConflict, map[string]any{
				"error":          "document conflict",
				"status":         "conflict",
				"path":           conflict.Path,
				"baseHash":       conflict.BaseHash,
				"currentHash":    conflict.CurrentHash,
				"currentContent": conflict.CurrentContent,
			})
			return
		}
		if errors.Is(err, sql.ErrNoRows) {
			writeJSONWithStatus(w, http.StatusNotFound, map[string]string{"error": "document not found"})
			return
		}
		writeJSONWithStatus(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
		return
	}

	writeJSONWithStatus(w, http.StatusOK, map[string]any{
		"status": "saved",
		"path":   page.Path,
		"title":  page.Title,
		"hash":   page.Hash,
	})
}

func writeJSON(w http.ResponseWriter, status int, payload any) {
	writeJSONWithStatus(w, status, payload)
}

func writeJSONWithStatus(w http.ResponseWriter, status int, payload any) {
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(payload)
}

func trimEditSuffix(path string) (string, bool) {
	if path == "edit" {
		return "", true
	}
	if !strings.HasSuffix(path, "/edit") {
		return "", false
	}
	return strings.TrimSuffix(path, "/edit"), true
}

func isContentAssetPath(path string) bool {
	extension := strings.ToLower(filepath.Ext(path))
	return extension != "" && extension != ".md"
}

func buildBrowser(records []docs.DocumentRecord, activePath string) browserData {
	paths := make([]string, 0, len(records))
	titleByPath := make(map[string]string, len(records))
	indexByFolder := make(map[string]string)
	for _, record := range records {
		paths = append(paths, record.Path)
		titleByPath[record.Path] = record.Title
		if folder, ok := indexFolder(record.Path); ok {
			indexByFolder[folder] = record.Path
		}
	}

	prefixes := []string{""}
	if activePath != "" {
		parts := strings.Split(activePath, "/")
		limit := len(parts)
		if strings.HasSuffix(activePath, ".md") {
			limit = len(parts) - 1
		}
		for i := 1; i <= limit; i++ {
			prefixes = append(prefixes, strings.Join(parts[:i], "/"))
		}
	}

	columns := make([]browserColumn, 0, len(prefixes))
	for _, prefix := range prefixes {
		column := browserColumn{
			Title: columnTitle(prefix),
			Items: buildBrowserItems(paths, titleByPath, indexByFolder, prefix, activePath),
		}
		if len(column.Items) > 0 {
			columns = append(columns, column)
		}
	}

	return browserData{Columns: columns}
}

func buildBrowserItems(paths []string, titleByPath map[string]string, indexByFolder map[string]string, prefix string, activePath string) []browserItem {
	seenFolders := make(map[string]browserItem)
	files := make([]browserItem, 0)
	prefixWithSlash := ""
	if prefix != "" {
		prefixWithSlash = prefix + "/"
	}

	for _, path := range paths {
		if shouldHideIndexFile(path, prefix) {
			continue
		}

		if prefix != "" && !strings.HasPrefix(path, prefixWithSlash) {
			continue
		}

		remainder := strings.TrimPrefix(path, prefixWithSlash)
		if remainder == "" {
			continue
		}

		if slash := strings.Index(remainder, "/"); slash >= 0 {
			name := remainder[:slash]
			folderPath := name
			if prefix != "" {
				folderPath = prefix + "/" + name
			}
			indexPath, hasIndex := indexByFolder[folderPath]
			url := "/?folder=" + folderPath
			if hasIndex {
				url = "/docs/" + strings.TrimSuffix(indexPath, "/index.md")
			}
			seenFolders[folderPath] = browserItem{
				Name:     displayFolderName(name, indexPath, titleByPath),
				Path:     folderPath,
				URL:      url,
				IsFolder: true,
				HasIndex: hasIndex,
				Active:   activePath == folderPath || strings.HasPrefix(activePath, folderPath+"/"),
			}
			continue
		}

		files = append(files, browserItem{
			Name:    displayDocumentName(path, titleByPath[path]),
			Path:    path,
			URL:     "/docs/" + strings.TrimSuffix(path, ".md"),
			IsIndex: path == "index.md" || strings.HasSuffix(path, "/index.md"),
			Active:  activePath == path,
		})
	}

	folders := make([]browserItem, 0, len(seenFolders))
	for _, item := range seenFolders {
		folders = append(folders, item)
	}
	sort.Slice(folders, func(i, j int) bool {
		return strings.ToLower(folders[i].Name) < strings.ToLower(folders[j].Name)
	})
	sort.Slice(files, func(i, j int) bool {
		return strings.ToLower(files[i].Name) < strings.ToLower(files[j].Name)
	})

	items := append(folders, files...)
	return items
}

func columnTitle(prefix string) string {
	if prefix == "" {
		return "Content"
	}
	return filepath.Base(prefix)
}

func displayDocumentName(path string, title string) string {
	if title != "" && title != "Untitled" {
		return title
	}
	return strings.TrimSuffix(filepath.Base(path), ".md")
}

func displayFolderName(name string, indexPath string, titleByPath map[string]string) string {
	if indexPath == "" {
		return name
	}
	if title := titleByPath[indexPath]; title != "" && title != "Untitled" {
		return title
	}
	return name
}

func indexFolder(path string) (string, bool) {
	if path == "index.md" {
		return "", true
	}
	if !strings.HasSuffix(path, "/index.md") {
		return "", false
	}
	return strings.TrimSuffix(path, "/index.md"), true
}

func shouldHideIndexFile(path string, prefix string) bool {
	if path == "index.md" {
		return false
	}
	if !strings.HasSuffix(path, "/index.md") {
		return false
	}
	folder := strings.TrimSuffix(path, "/index.md")
	return folder == prefix
}

func buildBreadcrumbs(path string) []breadcrumb {
	crumbs := []breadcrumb{
		{Name: "Content", URL: "/"},
	}
	if path == "" {
		return crumbs
	}

	cleanPath := strings.TrimSuffix(path, "/index.md")
	cleanPath = strings.TrimSuffix(cleanPath, ".md")
	parts := strings.Split(cleanPath, "/")
	currentPath := ""
	for _, part := range parts {
		if part == "" {
			continue
		}
		if currentPath == "" {
			currentPath = part
		} else {
			currentPath = currentPath + "/" + part
		}
		crumbs = append(crumbs, breadcrumb{
			Name: part,
			URL:  "/docs/" + currentPath,
		})
	}
	return crumbs
}