package handler

import (
	"encoding/json"
	"net/http"
	"os"
	"path/filepath"

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

// writeError is the JSON envelope used by admin-write endpoints to
// surface zddc.ValidateFile field errors back to the caller.
type writeError struct {
	Errors []zddc.FieldError `json:"errors"`
}

// projectCreateRequest is the wire shape for POST /.profile/projects.
//
// All fields except parent and name are optional. The ACL/admins/title
// fields are bundled into a starter .zddc only if at least one is supplied;
// otherwise the new directory is left empty and inherits ACL from its
// ancestors.
type projectCreateRequest struct {
	Parent string         `json:"parent"`
	Name   string         `json:"name"`
	Title  string         `json:"title,omitempty"`
	ACL    *zddc.ACLRules `json:"acl,omitempty"`
	Admins []string       `json:"admins,omitempty"`
}

// projectCreateResponse is the success payload.
type projectCreateResponse struct {
	Path string `json:"path"`
	URL  string `json:"url"`
}

// serveProfileProjectsCreate handles POST /.profile/projects.
//
// Authorization is the cascade's ActionCreate verb at the prospective
// parent directory — the same `c` permission used everywhere else.
// Super-admins pass via the decider's IsActiveAdmin bypass; explicitly
// granted principals (e.g., `*@example.com: c` on the root .zddc) pass
// via the normal ACL path. Non-authorized callers receive 404 to keep
// this endpoint's existence hidden alongside the rest of /.profile.
//
// The new project's .zddc is seeded with the creator's email in
// `admins:` (unless the request body supplied an explicit list). That
// makes them subtree admin of their own project from birth — they can
// manage deeper .zddc files, define roles, set per-stage ACLs. The
// strict-ancestor rule still applies to /<project>/.zddc itself; that
// stays editable only by ancestor admins (root super-admins).
func serveProfileProjectsCreate(cfg config.Config, w http.ResponseWriter, r *http.Request) {
	p := PrincipalFromContext(r)
	if r.Method != http.MethodPost {
		w.Header().Set("Allow", "POST")
		http.Error(w, "Method Not Allowed", http.StatusMethodNotAllowed)
		return
	}

	defer r.Body.Close()
	dec := json.NewDecoder(r.Body)
	dec.DisallowUnknownFields()
	var req projectCreateRequest
	if err := dec.Decode(&req); err != nil {
		http.Error(w, "Bad Request: "+err.Error(), http.StatusBadRequest)
		return
	}

	if err := zddc.ValidateProjectName(req.Name); err != nil {
		writeFieldError(w, http.StatusBadRequest, "name", err.Error())
		return
	}
	parentAbs, err := resolvePath(cfg.Root, req.Parent)
	if err != nil {
		http.NotFound(w, r)
		return
	}
	if pi, err := os.Stat(parentAbs); err != nil || !pi.IsDir() {
		http.Error(w, "Parent directory not found", http.StatusBadRequest)
		return
	}

	// Cascade-driven authorization: ActionCreate at the parent directory.
	// 404 (not 403) on deny to match the rest of /.profile/'s existence-
	// hiding policy.
	parentChain, err := zddc.EffectivePolicy(cfg.Root, parentAbs)
	if err != nil {
		http.Error(w, "Internal Server Error", http.StatusInternalServerError)
		return
	}
	parentRel, _ := filepath.Rel(cfg.Root, parentAbs)
	parentURL := "/"
	if parentRel != "." && parentRel != "" {
		parentURL = "/" + filepath.ToSlash(parentRel) + "/"
	}
	allowed, _ := policy.AllowActionFromChainP(r.Context(), DeciderFromContext(r), parentChain, p, parentURL, policy.ActionCreate)
	if !allowed {
		http.NotFound(w, r)
		return
	}

	newDir := filepath.Join(parentAbs, req.Name)
	if _, err := os.Stat(newDir); err == nil {
		http.Error(w, "Conflict: directory already exists", http.StatusConflict)
		return
	}

	// Always seed a starter .zddc — the creator becomes subtree admin of
	// their new project. Caller can also pass title / ACL / extra
	// admins on top.
	admins := req.Admins
	if len(admins) == 0 && p.Email != "" {
		admins = []string{p.Email}
	}
	var zf zddc.ZddcFile
	zf.Title = req.Title
	if req.ACL != nil {
		zf.ACL = *req.ACL
	}
	zf.Admins = admins
	wantsZddc := len(zf.Admins) > 0 || zf.Title != "" ||
		(req.ACL != nil && len(req.ACL.Permissions) > 0)
	if wantsZddc {
		if errs := zddc.ValidateFile(zf); len(errs) > 0 {
			w.Header().Set("Content-Type", "application/json; charset=utf-8")
			w.WriteHeader(http.StatusBadRequest)
			_ = json.NewEncoder(w).Encode(writeError{Errors: errs})
			return
		}
	}

	if err := os.MkdirAll(newDir, 0o755); err != nil {
		http.Error(w, "Internal Server Error: "+err.Error(), http.StatusInternalServerError)
		return
	}
	if wantsZddc {
		if err := zddc.WriteFile(newDir, zf); err != nil {
			// Best-effort rollback: remove the empty dir we just created.
			_ = os.Remove(newDir)
			http.Error(w, "Internal Server Error: "+err.Error(), http.StatusInternalServerError)
			return
		}
	}

	urlPath := urlPathOf(cfg.Root, newDir)
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	w.WriteHeader(http.StatusCreated)
	_ = json.NewEncoder(w).Encode(projectCreateResponse{
		Path: urlPath,
		URL:  urlPath + "/",
	})
}

// writeFieldError emits a single-error writeError JSON body — used when
// validation fails for a top-level scalar field like `name`.
func writeFieldError(w http.ResponseWriter, status int, field, message string) {
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(writeError{Errors: []zddc.FieldError{{Field: field, Message: message}}})
}