package apps

import (
	"path/filepath"
	"strings"
)

// AppAvailableAt reports whether app's virtual HTML can be served at
// requestDir. Rules (case-insensitive on canonical folder names):
//
//   - archive: every directory (multi-project, project, archive, party)
//   - browse: every directory (generic file listing — also the default
//     served at folder URLs without an index.html; see directory.go)
//   - classifier: requestDir is, or descends from, a folder named
//     "working", "staging", or "incoming" (the directories where
//     in-flight files get classified)
//   - mdedit: requestDir is, or descends from, a "working" or
//     "reviewing" folder. working/ is the drafting workspace;
//     reviewing/ is the virtual aggregation view of pending review
//     responses (server-rendered listings; mdedit follows the
//     listing's canonical URLs via the polyfill).
//   - transmittal: requestDir is, or descends from, a "staging" folder
//     (where outgoing transmittals are prepared)
//   - landing: only at the deployment root (the project picker)
//
// Operators can always drop a real <name>.html file at any path to
// override — that path is served by the static handler regardless of
// this function's result. AppAvailableAt is consulted only when no
// real file exists.
//
// In the canonical layout, "incoming" only appears at
// archive/<party>/incoming/, so checking "any ancestor named incoming"
// is equivalent to checking "under a per-party incoming folder."
func AppAvailableAt(root, requestDir, app string) bool {
	root = filepath.Clean(root)
	requestDir = filepath.Clean(requestDir)

	switch app {
	case "archive", "browse":
		return true
	case "landing":
		return requestDir == root
	case "classifier":
		return inAncestorWithName(root, requestDir, "working", "staging", "incoming")
	case "mdedit":
		return inAncestorWithName(root, requestDir, "working", "reviewing")
	case "transmittal":
		return inAncestorWithName(root, requestDir, "staging")
	}
	return false
}

// inAncestorWithName reports whether requestDir is, or has an ancestor
// (not including root itself), whose last segment case-folds to one
// of names. Match is on segment names, case-insensitively.
func inAncestorWithName(root, requestDir string, names ...string) bool {
	if requestDir == root {
		return false
	}
	rel, err := filepath.Rel(root, requestDir)
	if err != nil || strings.HasPrefix(rel, "..") {
		return false
	}
	for _, part := range strings.Split(rel, string(filepath.Separator)) {
		for _, n := range names {
			if strings.EqualFold(part, n) {
				return true
			}
		}
	}
	return false
}

// DefaultAppAt returns the canonical default tool name for requestDir,
// or "" if no specific tool fits. Used by the dispatcher to decide
// which app to serve at a directory URL with no trailing slash —
// trailing-slash URLs serve the browse app for any directory.
//
// Rules (case-insensitive on canonical folder names):
//
//   - <project>/archive/<party>/mdl/...    → "tables"
//   - <project>/archive/                   → "archive"
//   - <project>/archive/<party>/...        → "archive"
//   - <project>/staging/...                → "transmittal"
//   - <project>/working/...                → "mdedit"
//   - <project>/reviewing/...              → "mdedit" (operates on the
//                                              virtual aggregator listing)
//   - any other directory                  → "" (no default)
//
// The mdl rule wins over the broader archive rule because the table
// editor is a more specific surface for browsing planned deliverables
// than the archive index. Note: the dir at archive/<party>/mdl/
// itself IS the table — its table.yaml + form.yaml + row YAMLs all
// live there together (self-contained directory).
//
// requestDir and root are absolute filesystem paths; requestDir must
// be under root (otherwise "" is returned).
func DefaultAppAt(root, requestDir string) string {
	root = filepath.Clean(root)
	requestDir = filepath.Clean(requestDir)
	if requestDir == root {
		return ""
	}
	rel, err := filepath.Rel(root, requestDir)
	if err != nil || strings.HasPrefix(rel, "..") {
		return ""
	}
	parts := strings.Split(rel, string(filepath.Separator))
	if len(parts) < 2 {
		// Project root itself — no default tool.
		return ""
	}
	// The project segment is parts[0]; canonical folder is parts[1].
	canonical := strings.ToLower(parts[1])
	switch canonical {
	case "archive":
		// Inside archive/. Check for the mdl sub-case at depth 4
		// (parts: project, archive, party, mdl).
		if len(parts) >= 4 && strings.EqualFold(parts[3], "mdl") {
			return "tables"
		}
		return "archive"
	case "staging":
		return "transmittal"
	case "working":
		return "mdedit"
	case "reviewing":
		return "mdedit"
	}
	return ""
}