package httpserver

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

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

	"github.com/tim/md-hub-secure/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
}

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) {
	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:        "MD Hub Secure",
		WebEnabled:   s.webEnabled,
		BodyClass:    "page-index",
		BodyTemplate: "index_content",
		Data: indexData{
			Browser: buildBrowser(items, activeFolder),
		},
	})
}

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, "*")
	s.renderDocumentPage(w, r, pagePath)
}

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),
		},
	})
}

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) 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 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 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
}