package handler

import (
	"encoding/json"
	"log/slog"
	"net/http"
	"path/filepath"
	"strings"

	"codeberg.org/VARASYS/ZDDC/zddc/internal/archive"
	"codeberg.org/VARASYS/ZDDC/zddc/internal/config"
	"codeberg.org/VARASYS/ZDDC/zddc/internal/listing"
	"codeberg.org/VARASYS/ZDDC/zddc/internal/zddc"
)

// ServeArchive handles requests under a .archive virtual path segment.
//
// .archive is exposed at every folder depth so HTML produced for offline use
// can reference sibling tracking numbers via "../.archive/<tracking>.html".
// In a browser the relative link is resolved before the request reaches the
// server, so the contextPath the request arrives under is significant: its
// FIRST segment is the project, and the .archive listing/resolver is scoped
// to that project's bucket. This avoids cross-project collisions when the
// same tracking number is issued under multiple projects.
//
// contextPath: the URL path leading up to (but not including) .archive
//   - first segment selects the project bucket
//   - used to gate the listing endpoint via cascading .zddc ACL
//   - used as the URL prefix for the entries returned in the listing
//   - empty (root /.archive/) returns 404 — refs must be project-rooted
//
// filename:    the part after .archive/ (empty for directory listing)
func ServeArchive(cfg config.Config, idx *archive.Index, w http.ResponseWriter, r *http.Request, contextPath, filename string) {
	email := EmailFromContext(r)

	project := projectFromContextPath(contextPath)
	if project == "" {
		http.Error(w, "Not Found: .archive must be requested under a project directory (e.g. /<project>/.archive/)", http.StatusNotFound)
		return
	}

	// ACL gate on the context directory: callers who can't reach the
	// directory hosting this .archive shouldn't be able to query it either.
	dirPath := strings.TrimPrefix(contextPath, "/")
	dirPath = strings.TrimSuffix(dirPath, "/")
	absDir := filepath.Join(cfg.Root, filepath.FromSlash(dirPath))
	chain, err := zddc.EffectivePolicy(cfg.Root, absDir)
	if err != nil {
		slog.Warn("ACL policy error", "path", absDir, "err", err)
	}
	if !zddc.AllowedWithChain(chain, email) {
		http.Error(w, "Forbidden", http.StatusForbidden)
		return
	}

	if filename == "" {
		serveArchiveListing(cfg, idx, w, r, contextPath, project, email)
		return
	}

	target, ok := archive.Resolve(idx, project, filename)
	if !ok {
		http.Error(w, "Not Found", http.StatusNotFound)
		return
	}

	// Per-target ACL: the resolved file may live in a subtree the caller
	// can't reach even though they could reach the contextPath. 404 (not
	// 403) so the tracking number's mere existence isn't disclosed.
	fileDir := filepath.Dir(filepath.Join(cfg.Root, filepath.FromSlash(target)))
	chain, err = zddc.EffectivePolicy(cfg.Root, fileDir)
	if err != nil {
		slog.Warn("ACL policy error on resolved file", "path", fileDir, "err", err)
	}
	if !zddc.AllowedWithChain(chain, email) {
		http.Error(w, "Not Found", http.StatusNotFound)
		return
	}

	http.Redirect(w, r, "/"+target, http.StatusFound)
}

// projectFromContextPath returns the first non-empty segment of the
// contextPath, which is the project bucket key for archive lookups. Returns
// "" for "/" or "" (root .archive — has no project).
func projectFromContextPath(contextPath string) string {
	cleaned := strings.Trim(contextPath, "/")
	if cleaned == "" {
		return ""
	}
	if i := strings.IndexByte(cleaned, '/'); i >= 0 {
		return cleaned[:i]
	}
	return cleaned
}

func serveArchiveListing(cfg config.Config, idx *archive.Index, w http.ResponseWriter, r *http.Request, contextPath, project, email string) {
	allEntries := idx.AllEntries(project)
	archiveBase := contextPath
	if !strings.HasSuffix(archiveBase, "/") {
		archiveBase += "/"
	}
	archiveBase += cfg.IndexPath + "/"

	// ACL chains are folder-keyed and the listing typically hits the same
	// few directories repeatedly (one per transmittal folder), so cache the
	// allow/deny decision per directory rather than re-walking .zddc files
	// for every entry.
	aclCache := make(map[string]bool)
	allowed := func(targetPath string) bool {
		fileDir := filepath.Dir(filepath.Join(cfg.Root, filepath.FromSlash(targetPath)))
		if v, ok := aclCache[fileDir]; ok {
			return v
		}
		chain, err := zddc.EffectivePolicy(cfg.Root, fileDir)
		if err != nil {
			aclCache[fileDir] = false
			return false
		}
		v := zddc.AllowedWithChain(chain, email)
		aclCache[fileDir] = v
		return v
	}

	var result []listing.FileInfo
	for _, e := range allEntries {
		if !allowed(e.TargetPath) {
			continue
		}
		result = append(result, listing.FileInfo{
			Name:  e.URLName,
			URL:   archiveBase + e.URLName,
			IsDir: false,
		})
	}

	w.Header().Set("Content-Type", "application/json")
	w.Header().Set("Cache-Control", "no-cache")
	if err := json.NewEncoder(w).Encode(result); err != nil {
		slog.Error("encoding archive listing", "err", err)
	}
}