// Copyright 2023 Princess B33f Heavy Industries / Dave Shanley
// SPDX-License-Identifier: MIT

package index

import (
	"errors"
	"fmt"
	"gopkg.in/yaml.v3"
	"io"
	"io/fs"
	"net/url"
	"os"
	"path/filepath"
	"sort"
	"sync"
	"time"
)

// CanBeIndexed is an interface that allows a file to be indexed.
type CanBeIndexed interface {
	Index(config *SpecIndexConfig) (*SpecIndex, error)
}

// RolodexFile is an interface that represents a file in the rolodex. It combines multiple `fs` interfaces
// like `fs.FileInfo` and `fs.File` into one interface, so the same struct can be used for everything.
type RolodexFile interface {
	GetContent() string
	GetFileExtension() FileExtension
	GetFullPath() string
	GetErrors() []error
	GetContentAsYAMLNode() (*yaml.Node, error)
	GetIndex() *SpecIndex
	Name() string
	ModTime() time.Time
	IsDir() bool
	Sys() any
	Size() int64
	Mode() os.FileMode
}

// RolodexFS is an interface that represents a RolodexFS, is the same interface as `fs.FS`, except it
// also exposes a GetFiles() signature, to extract all files in the FS.
type RolodexFS interface {
	Open(name string) (fs.File, error)
	GetFiles() map[string]RolodexFile
}

// Rolodex is a file system abstraction that allows for the indexing of multiple file systems
// and the ability to resolve references across those file systems. It is used to hold references to external
// files, and the indexes they hold. The rolodex is the master lookup for all references.
type Rolodex struct {
	localFS                    map[string]fs.FS
	remoteFS                   map[string]fs.FS
	indexed                    bool
	built                      bool
	manualBuilt                bool
	resolved                   bool
	circChecked                bool
	indexConfig                *SpecIndexConfig
	indexingDuration           time.Duration
	indexes                    []*SpecIndex
	rootIndex                  *SpecIndex
	rootNode                   *yaml.Node
	caughtErrors               []error
	safeCircularReferences     []*CircularReferenceResult
	infiniteCircularReferences []*CircularReferenceResult
	ignoredCircularReferences  []*CircularReferenceResult
}

// NewRolodex creates a new rolodex with the provided index configuration.
func NewRolodex(indexConfig *SpecIndexConfig) *Rolodex {
	r := &Rolodex{
		indexConfig: indexConfig,
		localFS:     make(map[string]fs.FS),
		remoteFS:    make(map[string]fs.FS),
	}
	indexConfig.Rolodex = r
	return r
}

// GetIgnoredCircularReferences returns a list of circular references that were ignored during the indexing process.
// These can be array or polymorphic references.
func (r *Rolodex) GetIgnoredCircularReferences() []*CircularReferenceResult {
	debounced := make(map[string]*CircularReferenceResult)
	for _, c := range r.ignoredCircularReferences {
		if _, ok := debounced[c.LoopPoint.FullDefinition]; !ok {
			debounced[c.LoopPoint.FullDefinition] = c
		}
	}
	var debouncedResults []*CircularReferenceResult
	for _, v := range debounced {
		debouncedResults = append(debouncedResults, v)
	}
	return debouncedResults
}

// GetIndexingDuration returns the duration it took to index the rolodex.
func (r *Rolodex) GetIndexingDuration() time.Duration {
	return r.indexingDuration
}

// GetRootIndex returns the root index of the rolodex (the entry point, the main document)
func (r *Rolodex) GetRootIndex() *SpecIndex {
	return r.rootIndex
}

// GetRootNode returns the root index of the rolodex (the entry point, the main document)
func (r *Rolodex) GetRootNode() *yaml.Node {
	return r.rootNode
}

// GetIndexes returns all the indexes in the rolodex.
func (r *Rolodex) GetIndexes() []*SpecIndex {
	return r.indexes
}

// GetCaughtErrors returns all the errors that were caught during the indexing process.
func (r *Rolodex) GetCaughtErrors() []error {
	return r.caughtErrors
}

// AddLocalFS adds a local file system to the rolodex.
func (r *Rolodex) AddLocalFS(baseDir string, fileSystem fs.FS) {
	absBaseDir, _ := filepath.Abs(baseDir)
	r.localFS[absBaseDir] = fileSystem
}

// SetRootNode sets the root node of the rolodex (the entry point, the main document)
func (r *Rolodex) SetRootNode(node *yaml.Node) {
	r.rootNode = node
}

// AddRemoteFS adds a remote file system to the rolodex.
func (r *Rolodex) AddRemoteFS(baseURL string, fileSystem fs.FS) {
	r.remoteFS[baseURL] = fileSystem
}

// IndexTheRolodex indexes the rolodex, building out the indexes for each file, and then building the root index.
func (r *Rolodex) IndexTheRolodex() error {
	if r.indexed {
		return nil
	}

	var caughtErrors []error

	var indexBuildQueue []*SpecIndex

	indexRolodexFile := func(
		location string, fs fs.FS,
		doneChan chan bool,
		errChan chan error,
		indexChan chan *SpecIndex) {

		var wg sync.WaitGroup

		indexFileFunc := func(idxFile CanBeIndexed, fullPath string) {
			defer wg.Done()

			// copy config and set the
			copiedConfig := *r.indexConfig
			copiedConfig.SpecAbsolutePath = fullPath
			copiedConfig.AvoidBuildIndex = true // we will build out everything in two steps.
			idx, err := idxFile.Index(&copiedConfig)

			if err != nil {
				errChan <- err
			}

			if err == nil {
				// for each index, we need a resolver
				resolver := NewResolver(idx)

				// check if the config has been set to ignore circular references in arrays and polymorphic schemas
				if copiedConfig.IgnoreArrayCircularReferences {
					resolver.IgnoreArrayCircularReferences()
				}
				if copiedConfig.IgnorePolymorphicCircularReferences {
					resolver.IgnorePolymorphicCircularReferences()
				}
				indexChan <- idx
			}

		}

		if lfs, ok := fs.(RolodexFS); ok {
			wait := false
			for _, f := range lfs.GetFiles() {
				if idxFile, ko := f.(CanBeIndexed); ko {
					wg.Add(1)
					wait = true
					go indexFileFunc(idxFile, f.GetFullPath())
				}
			}
			if wait {
				wg.Wait()
			}
			doneChan <- true
			return
		} else {
			errChan <- errors.New("rolodex file system is not a RolodexFS")
			doneChan <- true
		}
	}

	indexingCompleted := 0
	totalToIndex := len(r.localFS) + len(r.remoteFS)
	doneChan := make(chan bool)
	errChan := make(chan error)
	indexChan := make(chan *SpecIndex)

	// run through every file system and index every file, fan out as many goroutines as possible.
	started := time.Now()
	for k, v := range r.localFS {
		go indexRolodexFile(k, v, doneChan, errChan, indexChan)
	}
	for k, v := range r.remoteFS {
		go indexRolodexFile(k, v, doneChan, errChan, indexChan)
	}

	for indexingCompleted < totalToIndex {
		select {
		case <-doneChan:
			indexingCompleted++
		case err := <-errChan:
			indexingCompleted++
			caughtErrors = append(caughtErrors, err)
		case idx := <-indexChan:
			indexBuildQueue = append(indexBuildQueue, idx)
		}
	}

	// now that we have indexed all the files, we can build the index.
	r.indexes = indexBuildQueue

	sort.Slice(indexBuildQueue, func(i, j int) bool {
		return indexBuildQueue[i].specAbsolutePath < indexBuildQueue[j].specAbsolutePath
	})

	for _, idx := range indexBuildQueue {
		idx.BuildIndex()
		if r.indexConfig.AvoidCircularReferenceCheck {
			continue
		}
		errs := idx.resolver.CheckForCircularReferences()
		for e := range errs {
			caughtErrors = append(caughtErrors, errs[e])
		}
		if len(idx.resolver.GetIgnoredCircularPolyReferences()) > 0 {
			r.ignoredCircularReferences = append(r.ignoredCircularReferences, idx.resolver.GetIgnoredCircularPolyReferences()...)
		}
		if len(idx.resolver.GetIgnoredCircularArrayReferences()) > 0 {
			r.ignoredCircularReferences = append(r.ignoredCircularReferences, idx.resolver.GetIgnoredCircularArrayReferences()...)
		}
	}

	// indexed and built every supporting file, we can build the root index (our entry point)
	if r.rootNode != nil {

		// if there is a base path, then we need to set the root spec config to point to a theoretical root.yaml
		// which does not exist, but is used to formulate the absolute path to root references correctly.
		if r.indexConfig.BasePath != "" && r.indexConfig.BaseURL == nil {

			basePath := r.indexConfig.BasePath
			if !filepath.IsAbs(basePath) {
				basePath, _ = filepath.Abs(basePath)
			}

			if len(r.localFS) > 0 || len(r.remoteFS) > 0 {
				r.indexConfig.SpecAbsolutePath = filepath.Join(basePath, "root.yaml")
			}
		}

		index := NewSpecIndexWithConfig(r.rootNode, r.indexConfig)
		resolver := NewResolver(index)

		if r.indexConfig.IgnoreArrayCircularReferences {
			resolver.IgnoreArrayCircularReferences()
		}
		if r.indexConfig.IgnorePolymorphicCircularReferences {
			resolver.IgnorePolymorphicCircularReferences()
		}

		index.BuildIndex()

		if !r.indexConfig.AvoidCircularReferenceCheck {
			resolvingErrors := resolver.CheckForCircularReferences()
			r.circChecked = true
			for e := range resolvingErrors {
				caughtErrors = append(caughtErrors, resolvingErrors[e])
			}
			if len(resolver.GetIgnoredCircularPolyReferences()) > 0 {
				r.ignoredCircularReferences = append(r.ignoredCircularReferences, resolver.GetIgnoredCircularPolyReferences()...)
			}
			if len(resolver.GetIgnoredCircularArrayReferences()) > 0 {
				r.ignoredCircularReferences = append(r.ignoredCircularReferences, resolver.GetIgnoredCircularArrayReferences()...)
			}
		}
		r.rootIndex = index
		if len(index.refErrors) > 0 {
			caughtErrors = append(caughtErrors, index.refErrors...)
		}
	}
	r.indexingDuration = time.Since(started)
	r.indexed = true
	r.caughtErrors = caughtErrors
	r.built = true
	return errors.Join(caughtErrors...)

}

// CheckForCircularReferences checks for circular references in the rolodex.
func (r *Rolodex) CheckForCircularReferences() {
	if !r.circChecked {
		if r.rootIndex != nil && r.rootIndex.resolver != nil {
			resolvingErrors := r.rootIndex.resolver.CheckForCircularReferences()
			for e := range resolvingErrors {
				r.caughtErrors = append(r.caughtErrors, resolvingErrors[e])
			}
			if len(r.rootIndex.resolver.ignoredPolyReferences) > 0 {
				r.ignoredCircularReferences = append(r.ignoredCircularReferences, r.rootIndex.resolver.ignoredPolyReferences...)
			}
			if len(r.rootIndex.resolver.ignoredArrayReferences) > 0 {
				r.ignoredCircularReferences = append(r.ignoredCircularReferences, r.rootIndex.resolver.ignoredArrayReferences...)
			}
			r.safeCircularReferences = append(r.safeCircularReferences, r.rootIndex.resolver.GetSafeCircularReferences()...)
			r.infiniteCircularReferences = append(r.infiniteCircularReferences, r.rootIndex.resolver.GetInfiniteCircularReferences()...)
		}
		r.circChecked = true
	}
}

// Resolve resolves references in the rolodex.
func (r *Rolodex) Resolve() {

	var resolvers []*Resolver
	if r.rootIndex != nil && r.rootIndex.resolver != nil {
		resolvers = append(resolvers, r.rootIndex.resolver)
	}
	for _, idx := range r.indexes {
		if idx.resolver != nil {
			resolvers = append(resolvers, idx.resolver)
		}
	}
	for _, res := range resolvers {
		resolvingErrors := res.Resolve()
		for e := range resolvingErrors {
			r.caughtErrors = append(r.caughtErrors, resolvingErrors[e])
		}
		if len(r.rootIndex.resolver.ignoredPolyReferences) > 0 {
			r.ignoredCircularReferences = append(r.ignoredCircularReferences, res.ignoredPolyReferences...)
		}
		if len(r.rootIndex.resolver.ignoredArrayReferences) > 0 {
			r.ignoredCircularReferences = append(r.ignoredCircularReferences, res.ignoredArrayReferences...)
		}
		r.safeCircularReferences = append(r.safeCircularReferences, res.GetSafeCircularReferences()...)
		r.infiniteCircularReferences = append(r.infiniteCircularReferences, res.GetInfiniteCircularReferences()...)
	}
	r.resolved = true
}

// BuildIndexes builds the indexes in the rolodex, this is generally not required unless manually building a rolodex.
func (r *Rolodex) BuildIndexes() {
	if r.manualBuilt {
		return
	}
	for _, idx := range r.indexes {
		idx.BuildIndex()
	}
	if r.rootIndex != nil {
		r.rootIndex.BuildIndex()
	}
	r.manualBuilt = true
}

// Open opens a file in the rolodex, and returns a RolodexFile.
func (r *Rolodex) Open(location string) (RolodexFile, error) {
	if r == nil {
		return nil, fmt.Errorf("rolodex has not been initialized, cannot open file '%s'", location)
	}

	if len(r.localFS) <= 0 && len(r.remoteFS) <= 0 {
		return nil, fmt.Errorf("rolodex has no file systems configured, cannot open '%s'. Add a BaseURL or BasePath to your configuration so the rolodex knows how to resolve references", location)
	}

	var errorStack []error
	var localFile *LocalFile
	var remoteFile *RemoteFile
	fileLookup := location
	isUrl := false
	u, _ := url.Parse(location)
	if u != nil && u.Scheme != "" {
		isUrl = true
	}

	if !isUrl {
		for k, v := range r.localFS {

			// check if this is a URL or an abs/rel reference.
			if !filepath.IsAbs(location) {
				fileLookup, _ = filepath.Abs(filepath.Join(k, location))
			}

			f, err := v.Open(fileLookup)
			if err != nil {
				// try a lookup that is not absolute, but relative
				f, err = v.Open(location)
				if err != nil {
					errorStack = append(errorStack, err)
					continue
				}
			}
			// check if this is a native rolodex FS, then the work is done.
			if lf, ko := interface{}(f).(*LocalFile); ko {
				localFile = lf
				break
			} else {
				// not a native FS, so we need to read the file and create a local file.
				bytes, rErr := io.ReadAll(f)
				if rErr != nil {
					errorStack = append(errorStack, rErr)
					continue
				}
				s, sErr := f.Stat()
				if sErr != nil {
					errorStack = append(errorStack, sErr)
					continue
				}
				if len(bytes) > 0 {
					localFile = &LocalFile{
						filename:     filepath.Base(fileLookup),
						name:         filepath.Base(fileLookup),
						extension:    ExtractFileType(fileLookup),
						data:         bytes,
						fullPath:     fileLookup,
						lastModified: s.ModTime(),
						index:        r.rootIndex,
					}
					break
				}
			}
		}

		if localFile == nil {

			// if there was no file found locally, then search the remote FS.
			for _, v := range r.remoteFS {
				f, err := v.Open(location)
				if err != nil {
					errorStack = append(errorStack, err)
					continue
				}
				if f != nil {
					return f.(*RemoteFile), nil
				}
			}
		}

	} else {

		if !r.indexConfig.AllowRemoteLookup {
			return nil, fmt.Errorf("remote lookup for '%s' not allowed, please set the index configuration to "+
				"AllowRemoteLookup to true", fileLookup)
		}

		for _, v := range r.remoteFS {
			f, err := v.Open(fileLookup)
			if err == nil {

				if rf, ok := interface{}(f).(*RemoteFile); ok {
					remoteFile = rf
					break
				} else {

					bytes, rErr := io.ReadAll(f)
					if rErr != nil {
						errorStack = append(errorStack, rErr)
						continue
					}
					s, sErr := f.Stat()
					if sErr != nil {
						errorStack = append(errorStack, sErr)
						continue
					}
					if len(bytes) > 0 {
						remoteFile = &RemoteFile{
							filename:     filepath.Base(fileLookup),
							name:         filepath.Base(fileLookup),
							extension:    ExtractFileType(fileLookup),
							data:         bytes,
							fullPath:     fileLookup,
							lastModified: s.ModTime(),
							index:        r.rootIndex,
						}
						break
					}
				}
			}
		}
	}

	if localFile != nil {
		return &rolodexFile{
			rolodex:   r,
			location:  localFile.fullPath,
			localFile: localFile,
		}, errors.Join(errorStack...)
	}

	if remoteFile != nil {
		return &rolodexFile{
			rolodex:    r,
			location:   remoteFile.fullPath,
			remoteFile: remoteFile,
		}, errors.Join(errorStack...)
	}

	return nil, errors.Join(errorStack...)
}