// Copyright 2022-2026 Princess B33f Heavy Industries / Dave Shanley
// SPDX-License-Identifier: MIT

package v3

import (
	"context"
	"fmt"
	"hash/maphash"
	"sync"

	"github.com/pb33f/libopenapi/datamodel"
	"github.com/pb33f/libopenapi/datamodel/low"
	"github.com/pb33f/libopenapi/index"
	"github.com/pb33f/libopenapi/orderedmap"
	"github.com/pb33f/libopenapi/utils"
	"go.yaml.in/yaml/v4"
)

// Paths represents a high-level OpenAPI 3+ Paths object, that is backed by a low-level one.
//
// Holds the relative paths to the individual endpoints and their operations. The path is appended to the URL from the
// Server Object in order to construct the full URL. The Paths MAY be empty, due to Access Control List (ACL)
// constraints.
//   - https://spec.openapis.org/oas/v3.1.0#paths-object
type Paths struct {
	PathItems  *orderedmap.Map[low.KeyReference[string], low.ValueReference[*PathItem]]
	Extensions *orderedmap.Map[low.KeyReference[string], low.ValueReference[*yaml.Node]]
	KeyNode    *yaml.Node
	RootNode   *yaml.Node
	index      *index.SpecIndex
	context    context.Context
	nodeStore  sync.Map
	reference  low.Reference
	*low.Reference
	low.NodeMap
}

// GetIndex returns the index.SpecIndex instance attached to the Paths object.
func (p *Paths) GetIndex() *index.SpecIndex {
	return p.index
}

// GetContext returns the context.Context instance used when building the Paths object.
func (p *Paths) GetContext() context.Context {
	return p.context
}

// GetRootNode returns the root yaml node of the Paths object.
func (p *Paths) GetRootNode() *yaml.Node {
	return p.RootNode
}

// GetKeyNode returns the key yaml node of the Paths object.
func (p *Paths) GetKeyNode() *yaml.Node {
	return p.KeyNode
}

// FindPath will attempt to locate a PathItem using the provided path string.
func (p *Paths) FindPath(path string) (result *low.ValueReference[*PathItem]) {
	for pair := orderedmap.First(p.PathItems); pair != nil; pair = pair.Next() {
		if pair.Key().Value == path {
			result = pair.ValuePtr()
			break
		}
	}
	return result
}

// FindPathAndKey attempts to locate a PathItem instance, given a path key.
func (p *Paths) FindPathAndKey(path string) (key *low.KeyReference[string], value *low.ValueReference[*PathItem]) {
	for pair := orderedmap.First(p.PathItems); pair != nil; pair = pair.Next() {
		if pair.Key().Value == path {
			key = pair.KeyPtr()
			value = pair.ValuePtr()
			break
		}
	}
	return key, value
}

// FindExtension will attempt to locate an extension using the specified string.
func (p *Paths) FindExtension(ext string) *low.ValueReference[*yaml.Node] {
	return low.FindItemInOrderedMap(ext, p.Extensions)
}

// GetExtensions returns all Paths extensions and satisfies the low.HasExtensions interface.
func (p *Paths) GetExtensions() *orderedmap.Map[low.KeyReference[string], low.ValueReference[*yaml.Node]] {
	return p.Extensions
}

// Build will extract extensions and all PathItems. This happens asynchronously for speed.
func (p *Paths) Build(ctx context.Context, keyNode, root *yaml.Node, idx *index.SpecIndex) error {
	root = utils.NodeAlias(root)
	p.KeyNode = keyNode
	p.RootNode = root
	utils.CheckForMergeNodes(root)
	p.reference = low.Reference{}
	p.Reference = &p.reference
	p.nodeStore = sync.Map{}
	p.Nodes = &p.nodeStore
	if keyNode != nil {
		p.AddNode(keyNode.Line, keyNode)
	}
	p.Extensions = low.ExtractExtensions(root)
	p.index = idx
	p.context = ctx

	low.ExtractExtensionNodes(ctx, p.Extensions, p.Nodes)

	pathsMap, err := extractPathItemsMap(ctx, root, idx)
	if err != nil {
		return err
	}

	p.PathItems = pathsMap

	for k, v := range pathsMap.FromOldest() {
		// add path as node to path item, not this path object.
		v.Value.Nodes.Store(k.KeyNode.Line, k.KeyNode)
	}

	return nil
}

// Hash will return a consistent Hash of the Paths object
func (p *Paths) Hash() uint64 {
	return low.WithHasher(func(h *maphash.Hash) uint64 {
		for _, hash := range low.AppendMapHashes(nil, p.PathItems) {
			h.WriteString(hash)
			h.WriteByte(low.HASH_PIPE)
		}
		for _, ext := range low.HashExtensions(p.Extensions) {
			h.WriteString(ext)
			h.WriteByte(low.HASH_PIPE)
		}
		return h.Sum64()
	})
}

func extractPathItemsMap(ctx context.Context, root *yaml.Node, idx *index.SpecIndex) (*orderedmap.Map[low.KeyReference[string], low.ValueReference[*PathItem]], error) {
	type buildResult struct {
		key   low.KeyReference[string]
		value low.ValueReference[*PathItem]
	}
	type buildInput struct {
		currentNode *yaml.Node
		pathNode    *yaml.Node
	}

	pathsMap := orderedmap.New[low.KeyReference[string], low.ValueReference[*PathItem]]()

	if root == nil {
		return pathsMap, nil
	}

	inputs := make([]buildInput, 0, len(root.Content)/2)
	skip := false
	var currentNode *yaml.Node
	for i, pathNode := range root.Content {
		if len(pathNode.Value) >= 2 && (pathNode.Value[0] == 'x' || pathNode.Value[0] == 'X') && pathNode.Value[1] == '-' {
			skip = true
			continue
		}
		if skip {
			skip = false
			continue
		}
		if i%2 == 0 {
			currentNode = pathNode
			continue
		}
		inputs = append(inputs, buildInput{
			currentNode: currentNode,
			pathNode:    pathNode,
		})
	}

	err := datamodel.TranslateSliceParallel(inputs,
		func(_ int, value buildInput) (buildResult, error) {
			pNode := value.pathNode
			cNode := value.currentNode

			foundContext := ctx
			var isRef bool
			var refNode *yaml.Node
			if ok, _, _ := utils.IsNodeRefValue(pNode); ok {
				isRef = true
				refNode = pNode
				r, _, err, fCtx := low.LocateRefNodeWithContext(ctx, pNode, idx)
				if r != nil {
					pNode = r
					foundContext = fCtx
					if err != nil && !idx.AllowCircularReferenceResolving() {
						return buildResult{}, fmt.Errorf("path item build failed: %s", err.Error())
					}
				} else {
					return buildResult{}, fmt.Errorf("path item build failed: cannot find reference: '%s' at line %d, col %d",
						pNode.Content[1].Value, pNode.Content[1].Line, pNode.Content[1].Column)
				}
			}

			path := new(PathItem)
			_ = low.BuildModel(pNode, path)
			err := path.Build(foundContext, cNode, pNode, idx)

			if isRef {
				path.SetReference(refNode.Content[1].Value, refNode)
			}

			if err != nil && idx != nil && idx.GetLogger() != nil {
				idx.GetLogger().Error(fmt.Sprintf("error building path item: %s", err.Error()))
			}

			return buildResult{
				key: low.KeyReference[string]{
					Value:   cNode.Value,
					KeyNode: cNode,
				},
				value: low.ValueReference[*PathItem]{
					Value:     path,
					ValueNode: pNode,
				},
			}, nil
		},
		func(result buildResult) error {
			pathsMap.Set(result.key, result.value)
			return nil
		},
	)
	if err != nil {
		return nil, err
	}
	return pathsMap, nil
}
