// Copyright (c) 2026 Storm Dragon
// Authors: Storm Dragon, Angus Kola
// SPDX-License-Identifier: GPL-3.0-or-later

package atspi

import "context"

// Owned by AccessibleTree under its mutex. Published data is immutable and can
// outlive a replacement; ValidateDocumentRange rejects retired views. Dirty
// flags stay in treeEntry, so an unrelated invalidation need not rebuild this.
type documentData struct {
	nodes   []DocumentNode
	indices map[ObjectID]int
	ends    []int
	rows    map[ObjectID][]ObjectReference
}

func new_document_data(nodes []DocumentNode) *documentData {
	data := &documentData{nodes: nodes, indices: make(map[ObjectID]int, len(nodes)), ends: make([]int, len(nodes))}
	for index, node := range nodes {
		data.indices[node.Reference.ID()] = index
		data.ends[index] = index
	}
	for index := len(nodes) - 1; index > 0; index-- {
		parent := data.indices[nodes[index].Parent]
		data.ends[parent] = max(data.ends[parent], data.ends[index])
	}
	return data
}

// SameContent identifies a shared immutable view, not merely matching object
// paths. A replacement with surviving identities still has different content.
func (document DocumentSnapshot) SameContent(other DocumentSnapshot) bool {
	return document.data != nil && document.data == other.data
}

func (document DocumentSnapshot) Index(id ObjectID) (int, bool) {
	if document.data != nil {
		index, ok := document.data.indices[id]
		return index, ok
	}
	for index, node := range document.Nodes {
		if node.Reference.ID() == id {
			return index, true
		}
	}
	return 0, false
}

func (document DocumentSnapshot) Node(id ObjectID) (DocumentNode, bool) {
	index, ok := document.Index(id)
	if !ok {
		return DocumentNode{}, false
	}
	return document.Nodes[index], true
}

func (document DocumentSnapshot) SubtreeEnd(index int) int {
	if document.data != nil {
		return document.data.ends[index]
	}
	end := index
	for next := index + 1; next < len(document.Nodes); next++ {
		parent, ok := document.Index(document.Nodes[next].Parent)
		if !ok || parent < index {
			break
		}
		end = next
	}
	return end
}

func document_entry_error(entry treeEntry) error {
	switch {
	case entry.snapshotInvalid:
		return ErrStaleSnapshot
	case entry.childrenInvalid:
		return ErrIncompleteTree
	case entry.textInvalid:
		return ErrStaleText
	case entry.geometryInvalid:
		return ErrStaleGeometry
	}
	return nil
}

// ValidateDocumentRange checks traversed objects, including skipped/hidden
// candidates, before committing a move. Ancestor metadata always matters;
// ancestor child order matters when crossing objects. A character move within
// one live leaf therefore survives insertions elsewhere in its parent.
func (tree *AccessibleTree) ValidateDocumentRange(ctx context.Context, document DocumentSnapshot, from, to int) error {
	tree.mu.RLock()
	defer tree.mu.RUnlock()
	return tree.validate_document_range_locked(ctx, document, from, to)
}

// ValidateDocumentOrder also checks ancestor child order when a structural
// search or a document-boundary jump will leave its current object.
func (tree *AccessibleTree) ValidateDocumentOrder(ctx context.Context, document DocumentSnapshot, index int) error {
	tree.mu.RLock()
	defer tree.mu.RUnlock()
	return tree.validate_document_path_locked(ctx, document, index, index, true)
}

func (tree *AccessibleTree) validate_document_range_locked(ctx context.Context, document DocumentSnapshot, from, to int) error {
	return tree.validate_document_path_locked(ctx, document, from, to, from != to)
}

func (tree *AccessibleTree) validate_document_path_locked(ctx context.Context, document DocumentSnapshot, from, to int, requireOrder bool) error {
	if err := ctx.Err(); err != nil {
		return err
	}
	if document.data == nil || tree.documents[document.Context.TopLevel.ID()] != document.data {
		return ErrStaleObject
	}
	if from < 0 || to < 0 || from >= len(document.Nodes) || to >= len(document.Nodes) {
		return ErrStaleObject
	}
	for index := min(from, to); index <= max(from, to); index++ {
		if err := ctx.Err(); err != nil {
			return err
		}
		node := document.Nodes[index]
		entry, err := tree.resolveLocked(node.Reference)
		if err != nil {
			return err
		}
		if err := document_entry_error(entry); err != nil {
			return err
		}
		if err := tree.validate_document_row_locked(document, node.Reference.ID()); err != nil {
			return err
		}
		for entry.hasParent {
			entry = tree.nodes[entry.parent]
			if entry.snapshotInvalid {
				return ErrStaleSnapshot
			}
			if entry.geometryInvalid {
				return ErrStaleGeometry
			}
			if requireOrder && entry.childrenInvalid {
				return ErrIncompleteTree
			}
			// Hypertext ranges interleave parent-owned text with embedded
			// children. An insertion can change those ranges without changing
			// the accessible child list. Refresh before crossing objects, while
			// allowing movement within an unchanged child to remain local.
			if requireOrder && entry.textInvalid && len(entry.snapshot.TextChildren) != 0 {
				return ErrStaleText
			}
			if err := tree.validate_document_row_locked(document, entry.snapshot.ID()); err != nil {
				return err
			}
		}
	}
	return nil
}

func (tree *AccessibleTree) validate_document_row_locked(document DocumentSnapshot, id ObjectID) error {
	for _, reference := range document.data.rows[id] {
		entry, err := tree.resolveLocked(reference)
		if err != nil {
			return err
		}
		if err := document_entry_error(entry); err != nil {
			return err
		}
	}
	return nil
}