package fs

import (
	"context"
	"net/url"
	"os"
	"path/filepath"
	"strings"

	"codeberg.org/VARASYS/ZDDC/zddc/internal/listing"
	"codeberg.org/VARASYS/ZDDC/zddc/internal/policy"
	"codeberg.org/VARASYS/ZDDC/zddc/internal/zddc"
)

// safeJoin joins fsRoot and relPath, then verifies the result is under fsRoot.
// Returns ("", false) if relPath would escape fsRoot.
func safeJoin(fsRoot, relPath string) (string, bool) {
	abs := filepath.Join(fsRoot, filepath.FromSlash(relPath))
	if !strings.HasPrefix(abs, fsRoot+string(filepath.Separator)) && abs != fsRoot {
		return "", false
	}
	return abs, true
}

// ListDirectory returns a Caddy-compatible JSON listing for the directory at
// filepath.Join(fsRoot, dirPath), filtered by ACL for userEmail.
//
// Rules:
//   - Hidden files (.-prefixed and _-prefixed) are excluded by default
//     unless includeHidden is true (typically driven by ?hidden=1 on
//     the request).
//   - *.portfolio files appear as virtual directories (stem + "/")
//   - Subdirectories for which the user lacks access are omitted (not 403'd inline)
//   - dirPath="" means the root of the served tree
//
// baseURL should end with "/" and is the URL prefix for this directory.
//
// The decider is queried per subdirectory; nil falls back to the internal
// Go evaluator (policy.InternalDecider) for tests that don't wire up
// an explicit decider.
func ListDirectory(ctx context.Context, decider policy.Decider, fsRoot, dirPath, userEmail, baseURL string, includeHidden, elevated bool) ([]listing.FileInfo, error) {
	if decider == nil {
		decider = &policy.InternalDecider{}
	}
	absDir, ok := safeJoin(fsRoot, dirPath)
	if !ok {
		return nil, os.ErrNotExist
	}

	// Virtual received/ window: when the URL points at <workflow>/received/
	// (i.e. the URL traverses a `received` segment whose workflow-folder
	// parent declares received_path in its .zddc), redirect the listing
	// source to the canonical received/<tracking>/ path. Entry URLs stay
	// rooted at baseURL so the browse client keeps the workflow context —
	// drag-drop onto an entry here PUTs to <workflow>/received/<file>,
	// which serveFilePut intercepts and rewrites to <workflow>/<base>+C<n><suffix>.
	if vr := zddc.ResolveVirtualReceived(fsRoot, strings.TrimSuffix(baseURL, "/")); vr.Resolved && vr.IsRoot {
		absDir = vr.ReceivedAbs
	}

	entries, err := os.ReadDir(absDir)
	if err != nil {
		// Empty-listing fallback for cascade-declared paths. A fresh
		// project doesn't have working/, staging/, reviewing/, or
		// archive/<party>/incoming/ on disk until something is
		// written into them — but the cascade (defaults.zddc.yaml
		// plus any on-disk overrides) declares them via paths:, so
		// the stage-strip / file nav can link unconditionally.
		// Returning [] gives a usable empty view; the
		// virtualUserHomeEntry below still fires for working/.
		if os.IsNotExist(err) && zddc.IsDeclaredPath(fsRoot, absDir) {
			entries = nil
		} else {
			return nil, err
		}
	}

	// Empty (not nil) so the JSON encoder emits [] rather than null
	// when no entries match — clients (browse, archive) expect an array.
	result := make([]listing.FileInfo, 0, len(entries))

	// Display overrides for this directory's children, sourced from
	// THIS directory's .zddc `display:` map. Built once and looked up
	// case-insensitively per entry. Empty map = no overrides.
	displayMap := readDisplayMap(absDir)

	// Set of cascade-declared child names (lowercase) for this dir.
	// Entries with a matching name get Declared=true so clients can
	// pick out the canonical-convention children without
	// re-implementing the cascade.
	declaredSet := make(map[string]bool)
	for _, name := range zddc.ChildrenDeclaredAt(fsRoot, absDir) {
		declaredSet[strings.ToLower(name)] = true
	}

	// Parent-dir chain + active-admin status. Files in this directory
	// inherit authorization from this chain, so we compute it once
	// and reuse for every file entry's Writable bit. Subdirectories
	// build their own chain (the child cascade can differ — e.g. a
	// per-user fenced home).
	parentChain, _ := zddc.EffectivePolicy(fsRoot, absDir)
	principal := zddc.Principal{Email: userEmail, Elevated: elevated}
	parentActiveAdmin := elevated && userEmail != "" &&
		zddc.IsAdminForChain(parentChain, userEmail)

	for _, entry := range entries {
		name := entry.Name()

		// Hidden file filter. '.' marks system/internal state (.zddc,
		// .converted/, .zddc.d/) and '_' marks operator scaffolding
		// (_app, _template). Both prefixes are hidden by default;
		// includeHidden=true (set via ?hidden=1 in the request) surfaces
		// them. The ACL chain still applies — anyone who can't read
		// the parent directory sees nothing regardless of this flag.
		if !includeHidden && (strings.HasPrefix(name, ".") || strings.HasPrefix(name, "_")) {
			continue
		}

		info, err := entry.Info()
		if err != nil {
			continue
		}

		isDir := entry.IsDir()
		displayName := lookupDisplay(displayMap, name)
		declared := declaredSet[strings.ToLower(name)]

		if isDir {
			// ACL check for subdirectory
			subAbs := filepath.Join(absDir, name)
			chain, err := zddc.EffectivePolicy(fsRoot, subAbs)
			if err != nil {
				continue
			}
			subURLPath := baseURL + name + "/"
			allowed, _ := policy.AllowFromChainP(ctx, decider, chain, principal, subURLPath)
			if !allowed {
				continue // omit denied directories silently
			}
			// Pull the title from this subdir's own .zddc, if it has
			// one. Lets clients render project / folder names without
			// a second round-trip per entry — the landing page used
			// to need a bespoke /api with this info; now the generic
			// listing carries it.
			var title string
			if zf, perr := zddc.ParseFile(filepath.Join(subAbs, ".zddc")); perr == nil {
				title = zf.Title
			}
			fi := listing.FileInfo{
				Name:        name + "/",
				Size:        info.Size(),
				URL:         baseURL + url.PathEscape(name) + "/",
				ModTime:     info.ModTime(),
				Mode:        uint32(info.Mode()),
				IsDir:       true,
				DisplayName: displayName,
				Declared:    declared,
				Title:       title,
			}
			result = append(result, fi)
			continue
		}

		// Regular file
		fi := listing.FileInfo{
			Name:        name,
			Size:        info.Size(),
			URL:         baseURL + url.PathEscape(name),
			ModTime:     info.ModTime(),
			Mode:        uint32(info.Mode()),
			IsDir:       false,
			DisplayName: displayName,
			Declared:    declared,
		}
		// Writable surfaces whether THIS principal could PUT this file
		// — same decision as the file API's authorizeAction would
		// reach. Uses the parent-dir chain (computed once above);
		// active-admin status short-circuits the per-file decider
		// query when the principal already holds admin authority.
		// .zddc requires ActionAdmin (not ActionWrite) so the verb
		// matches the file API's gate at fileapi.go:362-364.
		action := policy.ActionWrite
		if name == ".zddc" {
			action = policy.ActionAdmin
		}
		fileURL := baseURL + name
		if parentActiveAdmin {
			fi.Writable = true
		} else {
			allowed, _ := policy.AllowActionFromChainP(ctx, decider, parentChain, principal, fileURL, action)
			if allowed {
				fi.Writable = true
			}
		}
		result = append(result, fi)
	}

	// Per-user virtual home: when listing <project>/working/ for an
	// authenticated viewer, surface a synthetic <viewer-email>/ entry if
	// no real folder of any case variant already exists for them. A
	// first write to that path materialises a real folder with auto-own
	// .zddc; subsequent listings drop the synthetic entry naturally.
	if syn, ok := virtualUserHomeEntry(fsRoot, dirPath, userEmail, baseURL, result); ok {
		result = append(result, syn)
	}

	// At a project root, surface the four canonical project folders
	// (archive/working/staging/reviewing) as virtual entries when no
	// on-disk variant exists in any case. The browse client previously
	// did this client-side; moving it server-side lets the directory's
	// `display:` map apply to virtual entries the same way it applies
	// to real ones.
	result = append(result, virtualCanonicalFolders(fsRoot, absDir, baseURL, result, displayMap)...)

	// Workflow folder: append a virtual `received/` entry whose backing
	// is .zddc.received_path. The entry's URL stays under the workflow
	// folder (baseURL + "received/") so a click navigates "into" the
	// synthetic child — the listing handler then swaps the read source
	// to the canonical received/<tracking>/ path while keeping the URL
	// context intact. Suppressed if a real `received/` already exists on
	// disk (operator override).
	if rp := zddc.WorkflowReceivedPath(absDir); rp != "" {
		hasReal := false
		for _, fi := range result {
			if fi.IsDir && strings.EqualFold(strings.TrimSuffix(fi.Name, "/"), "received") {
				hasReal = true
				break
			}
		}
		if !hasReal {
			result = append(result, listing.FileInfo{
				Name:    "received/",
				URL:     baseURL + "received/",
				IsDir:   true,
				Virtual: true,
			})
		}
	}

	// Surface a virtual `.zddc` entry when the on-disk file doesn't
	// exist. The /<dir>/.zddc URL always serves SOMETHING — real
	// bytes if present, a synthetic placeholder body otherwise (see
	// handler.ServeZddcFile) — so the entry resolves to a real
	// editable view either way. PUT-ing back materialises the file
	// on disk and the listing converts to a real (non-virtual) row
	// automatically on the next fetch. Only emitted when the caller
	// asked for hidden entries (?hidden=1), matching the dot-prefix
	// hide rule used for every other dotfile.
	if includeHidden {
		if v, ok := virtualZddcEntry(ctx, decider, parentChain, principal, parentActiveAdmin, absDir, baseURL); ok {
			result = append(result, v)
		}
	}

	return result, nil
}

// virtualZddcEntry returns a synthetic listing entry for absDir/.zddc
// when no real file exists. The cascade has effective rules at every
// path (down through embedded defaults), so editing this virtual
// entry is always meaningful — a save promotes it to a real on-disk
// .zddc that overrides ancestor levels for this directory.
//
// Writable mirrors the real-file path: ActionAdmin against the parent
// chain, short-circuited when the principal already holds admin
// authority. An elevated admin sees writable=true and the editor lets
// them save; a non-admin sees writable=false and the editor mounts
// read-only.
func virtualZddcEntry(ctx context.Context, decider policy.Decider, parentChain zddc.PolicyChain, principal zddc.Principal, parentActiveAdmin bool, absDir, baseURL string) (listing.FileInfo, bool) {
	zddcPath := filepath.Join(absDir, ".zddc")
	if _, err := os.Stat(zddcPath); err == nil {
		return listing.FileInfo{}, false
	} else if !os.IsNotExist(err) {
		return listing.FileInfo{}, false
	}
	writable := parentActiveAdmin
	if !writable {
		allowed, _ := policy.AllowActionFromChainP(ctx, decider, parentChain, principal, baseURL+".zddc", policy.ActionAdmin)
		writable = allowed
	}
	return listing.FileInfo{
		Name:     ".zddc",
		URL:      baseURL + ".zddc",
		IsDir:    false,
		Virtual:  true,
		Writable: writable,
	}, true
}

// virtualCanonicalFolders returns synthetic entries for any
// cascade-declared child name that's absent from the on-disk
// listing. Sources from zddc.ChildrenDeclaredAt — the cascade's
// effective paths: at dirPath enumerates the expected children
// (archive, working, staging, reviewing at a project root; mdl,
// incoming, received, issued under archive/<party>/; whatever an
// operator added via on-disk .zddc paths:). Case-insensitive
// presence check suppresses a virtual entry when the on-disk
// directory exists in any case.
func virtualCanonicalFolders(fsRoot, absDir, baseURL string,
	real []listing.FileInfo, displayMap map[string]string) []listing.FileInfo {

	declared := zddc.ChildrenDeclaredAt(fsRoot, absDir)
	if len(declared) == 0 {
		return nil
	}

	present := make(map[string]bool, len(real))
	for _, fi := range real {
		if !fi.IsDir {
			continue
		}
		bare := strings.TrimSuffix(fi.Name, "/")
		present[strings.ToLower(bare)] = true
	}

	var synth []listing.FileInfo
	for _, name := range declared {
		if present[strings.ToLower(name)] {
			continue
		}
		synth = append(synth, listing.FileInfo{
			Name:        name + "/",
			URL:         baseURL + url.PathEscape(name) + "/",
			IsDir:       true,
			Virtual:     true,
			DisplayName: lookupDisplay(displayMap, name),
			Declared:    true, // synthesized entries are by definition cascade-declared
		})
	}
	return synth
}

// virtualUserHomeEntry returns the synthetic <viewer-email>/ entry that
// should be appended to a working/ listing, or (zero, false) when no
// synthetic entry applies.
//
// Conditions for the entry to fire:
//   - dirPath case-folds to <project>/working at depth-2 of fsRoot
//   - viewerEmail is non-empty
//   - real does not already contain a directory entry that case-folds
//     to viewerEmail (so a materialised home doesn't get duplicated)
func virtualUserHomeEntry(fsRoot, dirPath, viewerEmail, baseURL string, real []listing.FileInfo) (listing.FileInfo, bool) {
	if viewerEmail == "" {
		return listing.FileInfo{}, false
	}
	rel := strings.Trim(filepath.ToSlash(dirPath), "/")
	parts := strings.Split(rel, "/")
	if len(parts) != 2 || !strings.EqualFold(parts[1], "working") {
		return listing.FileInfo{}, false
	}
	for _, fi := range real {
		if !fi.IsDir {
			continue
		}
		// fi.Name carries a trailing slash for dirs.
		bare := strings.TrimSuffix(fi.Name, "/")
		if strings.EqualFold(bare, viewerEmail) {
			return listing.FileInfo{}, false
		}
	}
	return listing.FileInfo{
		Name:    viewerEmail + "/",
		URL:     baseURL + url.PathEscape(viewerEmail) + "/",
		IsDir:   true,
		Virtual: true,
	}, true
}

// readDisplayMap parses dirAbs/.zddc and returns its Display map (or
// nil when the file doesn't exist or has no display block). All keys
// are case-folded to lowercase so lookupDisplay's case-insensitive
// match is a simple map read.
func readDisplayMap(dirAbs string) map[string]string {
	zf, err := zddc.ParseFile(filepath.Join(dirAbs, ".zddc"))
	if err != nil || len(zf.Display) == 0 {
		return nil
	}
	out := make(map[string]string, len(zf.Display))
	for k, v := range zf.Display {
		if v == "" {
			continue
		}
		out[strings.ToLower(strings.TrimSpace(k))] = v
	}
	return out
}

// lookupDisplay returns the custom display label for name (matched
// case-insensitively against displayMap's keys), or "" when no
// override applies.
func lookupDisplay(displayMap map[string]string, name string) string {
	if len(displayMap) == 0 {
		return ""
	}
	return displayMap[strings.ToLower(name)]
}