package server

import (
	"context"
	"errors"
	"net/http"
	"strings"

	"chat-agent-system/internal/auth"
	"chat-agent-system/internal/authz"
	"chat-agent-system/internal/docrevision"
	"chat-agent-system/internal/freedoc"
	"chat-agent-system/internal/projectinstance"
)

type docRevisionRef struct {
	Kind           string // controlled|freeform|orphan
	ProjectID      int64
	WorkDir        string
	LifecycleState string
	Markdown       string
	Title          string
	AuthorID       int64
}

func (s *Server) resolveDocRevisionRef(ctx context.Context, user *auth.UserAccount, docID string) (*docRevisionRef, error) {
	if strings.TrimSpace(docID) == "" {
		return nil, docrevision.ErrInvalidDocID
	}
	if s.gov() != nil {
		if doc, err := s.gov().GetDocument(ctx, docID); err == nil && doc != nil {
			ref := &docRevisionRef{
				Kind: "controlled", ProjectID: doc.ProjectID, WorkDir: doc.WorkDir,
				LifecycleState: string(doc.CurrentState), AuthorID: doc.AuthorID,
			}
			if s.docRev() != nil {
				if md, _, herr := s.docRev().HeadContent(ctx, docID); herr == nil && strings.TrimSpace(md) != "" {
					ref.Markdown = md
					return ref, nil
				}
			}
			if content, cErr := s.gov().ReadDocumentContent(ctx, docID, s.dataRoot()); cErr == nil && content != nil {
				ref.Markdown = content.Markdown
			}
			return ref, nil
		}
	}
	if s.freeDoc() != nil && user != nil {
		if detail, err := s.freeDoc().GetDocument(ctx, int(user.ID), docID); err == nil && detail != nil {
			return &docRevisionRef{
				Kind: "freeform", ProjectID: int64(detail.Document.ProjectID),
				LifecycleState: "drafting", Markdown: detail.Content, Title: detail.Document.Title,
			}, nil
		} else if errors.Is(err, freedoc.ErrForbidden) {
			return nil, docrevision.ErrForbidden
		}
	}
	return &docRevisionRef{Kind: "orphan", LifecycleState: "drafting"}, nil
}

func (s *Server) authorizeDocRevision(ctx context.Context, user *auth.UserAccount, ref *docRevisionRef, write bool) error {
	if user == nil || ref == nil {
		return authz.ErrForbidden
	}
	if ref.Kind == "orphan" {
		// Unknown doc IDs: never bootstrap a silent fake ledger (read or write).
		return docrevision.ErrNotFound
	}
	if ref.ProjectID > 0 {
		if s.authorizer() == nil {
			if s.failClosedAuthz() {
				return authz.ErrForbidden
			}
		} else if err := s.authorizer().RequireProjectAccessOrAdmin(ctx, ref.ProjectID, user.ID, s.isSystemAdminUser(ctx, user)); err != nil {
			return err
		}
	} else if ref.Kind == "controlled" {
		return authz.ErrForbidden
	}
	if write && ref.LifecycleState != "" && ref.LifecycleState != "drafting" {
		return docrevision.ErrLifecycleLocked
	}
	if write && ref.Kind == "controlled" && ref.AuthorID > 0 && user.ID != ref.AuthorID && !s.isSystemAdminUser(ctx, user) {
		return docrevision.ErrForbidden
	}
	return nil
}

func (s *Server) requireDocRevisionAccess(w http.ResponseWriter, r *http.Request, write bool) (*auth.UserAccount, string, *docRevisionRef, bool) {
	user, ok := s.requirePrincipal(w, r)
	if !ok {
		return nil, "", nil, false
	}
	docID := strings.TrimSpace(r.PathValue("doc_id"))
	if docID == "" {
		writeDocRevisionError(w, docrevision.ErrInvalidDocID)
		return nil, "", nil, false
	}
	ref, err := s.resolveDocRevisionRef(r.Context(), user, docID)
	if err != nil {
		writeDocRevisionError(w, err)
		return nil, "", nil, false
	}
	if err := s.authorizeDocRevision(r.Context(), user, ref, write); err != nil {
		if errors.Is(err, authz.ErrForbidden) || errors.Is(err, authz.ErrUnauthenticated) {
			writeAuthzError(w, err)
			return nil, "", nil, false
		}
		writeDocRevisionError(w, err)
		return nil, "", nil, false
	}
	if write && !s.enforceDocGovWorkflowAction(w, r.Context(), user.ID, docID, projectinstance.DocAccessActionEdit) {
		return nil, "", nil, false
	}
	return user, docID, ref, true
}

func (s *Server) dataRoot() string {
	if s != nil && s.cfg != nil && s.cfg.DataDir != "" {
		return s.cfg.DataDir
	}
	return "."
}

func (s *Server) bootstrapRevisionIfNeeded(ctx context.Context, user *auth.UserAccount, docID string, ref *docRevisionRef) (*docrevision.RevisionState, error) {
	rev := s.docRev()
	if rev == nil {
		return nil, errors.New("docrevision unavailable")
	}
	st, err := rev.GetRevisionState(ctx, docID)
	if err == nil {
		return st, nil
	}
	if !errors.Is(err, docrevision.ErrNotFound) {
		return nil, err
	}
	if ref != nil && ref.Kind == "orphan" {
		return nil, docrevision.ErrNotFound
	}
	md := ""
	if ref != nil {
		md = ref.Markdown
	}
	if strings.TrimSpace(md) == "" {
		return nil, docrevision.ErrNeedsContent
	}
	kind := "controlled"
	life := "drafting"
	var projectID int64
	workDir := ""
	if ref != nil {
		if ref.Kind != "" {
			kind = ref.Kind
		}
		life = ref.LifecycleState
		projectID = ref.ProjectID
		workDir = ref.WorkDir
	}
	actor := docrevision.ActorSnapshot{DisplayName: "bootstrap", Role: "system"}
	if user != nil {
		actor = docrevision.ActorSnapshot{DisplayName: user.Name, Role: "author", Duty: "author"}
	}
	return rev.EnsureBootstrap(ctx, docrevision.BootstrapRequest{
		DocID: docID, Kind: kind, Markdown: md, ProjectID: projectID,
		WorkDir: workDir, LifecycleState: life, Actor: actor,
	})
}