// this file handles YAML file reading and writing with comment preservation, using gopkg.in/yaml.v3's node tree to maintain all existing comments during regeneration.
package main

import (
	"fmt"
	"os"

	"gopkg.in/yaml.v3"

	"github.com/anchore/syft/internal/capabilities"
)

const autoGeneratedComment = "AUTO-GENERATED"

const capabilitiesHeaderComment = `This file is partially auto-generated. Run 'go generate ./internal/capabilities' to regenerate.
Fields marked AUTO-GENERATED will be updated during regeneration.
All 'capabilities' sections are MANUAL - edit these to describe cataloger behavior.

CAPABILITY SECTIONS:
  There are two types of capability sections depending on cataloger type:

  1. Generic catalogers (type=generic): Have capabilities at the PARSER level
     - Each parser function has its own capabilities section
     - Allows different parsers within the same cataloger to have different capabilities

  2. Custom catalogers (type=custom): Have capabilities at the CATALOGER level
     - Single capabilities section for the entire cataloger

CAPABILITIES FORMAT:
  Capabilities use a field-based format with defaults and optional conditional overrides:

  capabilities:
    - field: <field-name>           # dot-notation path (e.g., "license", "dependency.depth")
      default: <value>              # value when no conditions match
      conditions:                   # optional - conditional overrides evaluated in order
        - when: {ConfigField: val}  # when these config fields match (AND logic)
          value: <override-value>   # use this value instead
          comment: "explanation"    # optional - why this condition exists
      evidence:                     # optional - source code references
        - "StructName.FieldName"
      comment: "explanation"        # optional - general field explanation

DETECTOR CONDITIONS:
  Detectors (used by custom catalogers) can have optional conditions that control when
  they are active. This allows a single cataloger to have different detection behavior
  based on configuration.

  Structure:
    detectors:
      - method: glob                 # AUTO-GENERATED - detection method
        criteria: ["**/*.jar"]       # AUTO-GENERATED - patterns to match
        comment: "always active"     # MANUAL - optional explanation
      - method: glob
        criteria: ["**/*.zip"]
        conditions:                  # MANUAL - when this detector is active
          - when: {IncludeZipFiles: true}  # config fields that must match
            comment: "optional explanation"
        comment: "ZIP detection requires config"

  Notes:
    - Conditions reference fields from the cataloger's config struct
    - Multiple conditions in the array use OR logic (any condition can activate)
    - Multiple fields in a 'when' clause use AND logic (all must match)
    - Detectors without conditions are always active
    - Only custom catalogers support detectors with conditions

CONDITION EVALUATION:
  - Conditions are evaluated in array order (first match wins)
  - Multiple fields in a 'when' clause use AND logic (all must match)
  - Multiple conditions in the array use OR logic (first matching condition)
  - If no conditions match, the default value is used

CAPABILITY FIELDS:
  Standard capability field names and their value types:

  license: (boolean)
    Whether license information is available.
    Examples:
      default: true                 # always available
      default: false                # never available
      default: false                # requires configuration
        conditions:
          - when: {SearchRemoteLicenses: true}
            value: true

  dependency.depth: (array of strings)
    Which dependency depths can be discovered.
    Values: "direct" (immediate deps), "indirect" (transitive deps)
    Examples:
      default: [direct]                    # only immediate dependencies
      default: [direct, indirect]          # full transitive closure
      default: []                          # no dependency information

  dependency.edges: (string)
    Relationships between nodes and completeness of the dependency graph.
    Values:
      - ""         # dependencies found but no edges between them
      - "flat"     # single level of dependencies with edges to root package only
      - "reduced"  # transitive reduction (redundant edges removed)
      - "complete" # all relationships with accurate direct and indirect edges
    Examples:
      default: complete
      default: ""

  dependency.kinds: (array of strings)
    Types of dependencies that can be discovered.
    Values: "runtime", "dev", "build", "test", "optional"
    Examples:
      default: [runtime]                   # production dependencies only
      default: [runtime, dev]              # production and development
      default: [runtime, dev, build]       # all dependency types
      default: [runtime]                   # with conditional dev deps
        conditions:
          - when: {IncludeDevDeps: true}
            value: [runtime, dev]

  package_manager.files.listing: (boolean)
    Whether file listings are available (which files belong to the package).
    Examples:
      default: true
      default: false
        conditions:
          - when: {CaptureOwnedFiles: true}
            value: true

  package_manager.files.digests: (boolean)
    Whether file digests/checksums are included in listings.
    Examples:
      default: true
      default: false

  package_manager.package_integrity_hash: (boolean)
    Whether a hash for verifying package integrity is available.
    Examples:
      default: true
      default: false

EXAMPLES:

  # Simple cataloger with no configuration
  capabilities:
    - name: license
      default: true
      comment: "license field always present in package.json"
    - name: dependency.depth
      default: [direct]
    - name: dependency.edges
      default: ""
    - name: dependency.kinds
      default: [runtime]
      comment: "devDependencies not parsed by this cataloger"
    - name: package_manager.files.listing
      default: false
    - name: package_manager.files.digests
      default: false
    - name: package_manager.package_integrity_hash
      default: false

  # Cataloger with configuration-dependent capabilities
  capabilities:
    - name: license
      default: false
      conditions:
        - when: {SearchLocalModCacheLicenses: true}
          value: true
          comment: "searches for licenses in GOPATH mod cache"
        - when: {SearchRemoteLicenses: true}
          value: true
          comment: "fetches licenses from proxy.golang.org"
      comment: "license scanning requires configuration"
    - name: dependency.depth
      default: [direct, indirect]
    - name: dependency.edges
      default: flat
    - name: dependency.kinds
      default: [runtime, dev]
    - name: package_manager.files.listing
      default: false
    - name: package_manager.files.digests
      default: false
    - name: package_manager.package_integrity_hash
      default: true
      evidence:
        - "GolangBinaryBuildinfoEntry.H1Digest"`

// loadCapabilities loads the capabilities document from a YAML file.
// Returns both the parsed document and the original YAML node tree to preserve comments.
// Exported for use by the generator in generate/main.go
func loadCapabilities(path string) (*capabilities.Document, *yaml.Node, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		if os.IsNotExist(err) {
			// return empty document if file doesn't exist
			return &capabilities.Document{}, nil, nil
		}
		return nil, nil, fmt.Errorf("failed to read capabilities file: %w", err)
	}

	// parse into node tree to preserve comments
	var rootNode yaml.Node
	if err := yaml.Unmarshal(data, &rootNode); err != nil {
		return nil, nil, fmt.Errorf("failed to parse capabilities YAML into node tree: %w", err)
	}

	// also parse into struct for easy manipulation
	var doc capabilities.Document
	if err := yaml.Unmarshal(data, &doc); err != nil {
		return nil, nil, fmt.Errorf("failed to parse capabilities YAML into struct: %w", err)
	}

	return &doc, &rootNode, nil
}

// writeYAMLToFile writes a YAML node to a file with proper encoding
func writeYAMLToFile(path string, rootNode *yaml.Node) error {
	f, err := os.Create(path)
	if err != nil {
		return fmt.Errorf("failed to create file: %w", err)
	}
	defer f.Close()

	encoder := yaml.NewEncoder(f)
	encoder.SetIndent(2)
	if err := encoder.Encode(rootNode); err != nil {
		return fmt.Errorf("failed to write YAML: %w", err)
	}
	if err := encoder.Close(); err != nil {
		return fmt.Errorf("failed to close encoder: %w", err)
	}

	return nil
}

// addFieldComments adds comments to top-level fields in the YAML node
func addFieldComments(rootNode *yaml.Node) {
	// navigate to the mapping node (handle both DocumentNode and MappingNode)
	var mappingNode *yaml.Node
	if rootNode.Kind == yaml.DocumentNode && len(rootNode.Content) > 0 {
		mappingNode = rootNode.Content[0]
	} else {
		mappingNode = rootNode
	}

	if mappingNode != nil && len(mappingNode.Content) > 0 {
		// iterate through top-level keys
		for i := 0; i < len(mappingNode.Content); i += 2 {
			keyNode := mappingNode.Content[i]
			valueNode := mappingNode.Content[i+1]

			switch keyNode.Value {
			case "configs":
				// configs section is AUTO-GENERATED
				if keyNode.LineComment == "" {
					keyNode.LineComment = "AUTO-GENERATED - config structs and their fields"
				}
			case "application":
				// application section is AUTO-GENERATED
				if keyNode.LineComment == "" {
					keyNode.LineComment = "AUTO-GENERATED - application-level config keys"
				}
			case "catalogers":
				// clear any HeadComment on catalogers key and value nodes to prevent duplicate headers
				// (the only header should be on the root DocumentNode)
				keyNode.HeadComment = ""
				valueNode.HeadComment = ""
				addCatalogerComments(valueNode)
			}
		}
	}
}

// SaveCapabilities saves the capabilities document to a YAML file with comments.
// If existingNode is provided, it updates the existing node tree in-place to preserve comments.
// If existingNode is nil, it creates a new node tree.
func saveCapabilities(path string, doc *capabilities.Document, existingNode *yaml.Node) error {
	var rootNode yaml.Node

	if existingNode != nil {
		// update existing node tree in-place to preserve all comments
		rootNode = *existingNode
		rootNode.HeadComment = capabilitiesHeaderComment // update header before processing
		if err := updateNodeTree(&rootNode, doc); err != nil {
			return fmt.Errorf("failed to update node tree: %w", err)
		}
	} else {
		// create a new yaml.Node for new files
		if err := rootNode.Encode(doc); err != nil {
			return fmt.Errorf("failed to encode document: %w", err)
		}
		rootNode.HeadComment = capabilitiesHeaderComment
	}

	// add/update comments to fields
	addFieldComments(&rootNode)

	// write to file
	return writeYAMLToFile(path, &rootNode)
}

// updateNodeTree updates an existing YAML node tree with new document data
// while preserving all existing comments (HeadComment, LineComment, FootComment).
func updateNodeTree(rootNode *yaml.Node, doc *capabilities.Document) error {
	// encode the document into a new temporary node tree
	var newNode yaml.Node
	if err := newNode.Encode(doc); err != nil {
		return fmt.Errorf("failed to encode document: %w", err)
	}

	// get the mapping node from root
	var existingMapping *yaml.Node
	var newMapping *yaml.Node

	if rootNode.Kind == yaml.DocumentNode && len(rootNode.Content) > 0 {
		existingMapping = rootNode.Content[0]
	} else {
		existingMapping = rootNode
	}

	if newNode.Kind == yaml.DocumentNode && len(newNode.Content) > 0 {
		newMapping = newNode.Content[0]
	} else {
		newMapping = &newNode
	}

	if existingMapping == nil || newMapping == nil {
		*rootNode = newNode
		return nil
	}

	// update or add configs section (AUTO-GENERATED, no comment preservation needed)
	updateOrAddSection(existingMapping, newMapping, "configs")

	// update or add application section (AUTO-GENERATED, no comment preservation needed)
	updateOrAddSection(existingMapping, newMapping, "application")

	// update catalogers section (preserve comments)
	updateCatalogersSection(existingMapping, newMapping)

	return nil
}

// updateCatalogersSection updates the catalogers section while preserving comments
func updateCatalogersSection(existingMapping, newMapping *yaml.Node) {
	existingCatalogersNode := findSectionNode(existingMapping, "catalogers")
	newCatalogersNode := findSectionNode(newMapping, "catalogers")

	if existingCatalogersNode == nil || newCatalogersNode == nil {
		return
	}

	// create a map of existing cataloger nodes by name for quick lookup
	existingByName := make(map[string]*yaml.Node)
	if existingCatalogersNode.Kind == yaml.SequenceNode {
		for _, catalogerNode := range existingCatalogersNode.Content {
			if catalogerNode.Kind == yaml.MappingNode {
				name := findFieldValue(catalogerNode, "name")
				if name != "" {
					existingByName[name] = catalogerNode
				}
			}
		}
	}

	// update each cataloger in the new tree with preserved comments
	if newCatalogersNode.Kind == yaml.SequenceNode {
		for _, newCatalogerNode := range newCatalogersNode.Content {
			if newCatalogerNode.Kind != yaml.MappingNode {
				continue
			}

			name := findFieldValue(newCatalogerNode, "name")
			if existingNode := existingByName[name]; existingNode != nil {
				// preserve comments from existing cataloger entry
				newCatalogerNode.HeadComment = existingNode.HeadComment
				newCatalogerNode.LineComment = existingNode.LineComment
				newCatalogerNode.FootComment = existingNode.FootComment

				// preserve field-level and nested comments
				preserveFieldComments(existingNode, newCatalogerNode)
			}
		}
	}

	// replace the catalogers content
	existingCatalogersNode.Content = newCatalogersNode.Content
}

// updateOrAddSection updates or adds a section in the existing mapping from the new mapping
func updateOrAddSection(existingMapping, newMapping *yaml.Node, sectionName string) {
	if existingMapping.Kind != yaml.MappingNode || newMapping.Kind != yaml.MappingNode {
		return
	}

	newSection := findSectionNode(newMapping, sectionName)
	if newSection == nil {
		return
	}

	// find if section exists in existing mapping
	existingSectionIdx := -1
	for i := 0; i < len(existingMapping.Content); i += 2 {
		if existingMapping.Content[i].Value == sectionName {
			existingSectionIdx = i
			break
		}
	}

	if existingSectionIdx >= 0 {
		// replace existing section value
		existingMapping.Content[existingSectionIdx+1] = newSection
	} else {
		// add new section at the beginning (before catalogers)
		keyNode := &yaml.Node{
			Kind:  yaml.ScalarNode,
			Value: sectionName,
		}
		existingMapping.Content = append([]*yaml.Node{keyNode, newSection}, existingMapping.Content...)
	}
}

// findSectionNode finds a section node by name in a mapping node
func findSectionNode(mappingNode *yaml.Node, sectionName string) *yaml.Node {
	if mappingNode.Kind != yaml.MappingNode {
		return nil
	}

	for i := 0; i < len(mappingNode.Content); i += 2 {
		if mappingNode.Content[i].Value == sectionName && i+1 < len(mappingNode.Content) {
			return mappingNode.Content[i+1]
		}
	}

	return nil
}

// findFieldValue finds the value of a field in a mapping node
func findFieldValue(mappingNode *yaml.Node, fieldName string) string {
	if mappingNode.Kind != yaml.MappingNode {
		return ""
	}

	for i := 0; i < len(mappingNode.Content); i += 2 {
		if mappingNode.Content[i].Value == fieldName && i+1 < len(mappingNode.Content) {
			return mappingNode.Content[i+1].Value
		}
	}

	return ""
}

// preserveMappingNodeComments preserves comments for mapping nodes
func preserveMappingNodeComments(existingNode, newNode *yaml.Node) {
	// create maps of existing fields by key for both keys and values
	existingKeys := make(map[string]*yaml.Node)
	existingValues := make(map[string]*yaml.Node)
	for i := 0; i < len(existingNode.Content); i += 2 {
		keyNode := existingNode.Content[i]
		valueNode := existingNode.Content[i+1]
		existingKeys[keyNode.Value] = keyNode
		existingValues[keyNode.Value] = valueNode
	}

	// preserve comments for matching fields in new node
	for i := 0; i < len(newNode.Content); i += 2 {
		keyNode := newNode.Content[i]
		valueNode := newNode.Content[i+1]

		// preserve comments on the key node (for line comments like "# AUTO-GENERATED")
		if existingKey := existingKeys[keyNode.Value]; existingKey != nil {
			keyNode.HeadComment = existingKey.HeadComment
			keyNode.LineComment = existingKey.LineComment
			keyNode.FootComment = existingKey.FootComment
		}

		// preserve comments on the value node
		if existingValue := existingValues[keyNode.Value]; existingValue != nil {
			valueNode.HeadComment = existingValue.HeadComment
			valueNode.LineComment = existingValue.LineComment
			valueNode.FootComment = existingValue.FootComment

			// recursively preserve nested comments
			preserveFieldComments(existingValue, valueNode)
		}
	}
}

// preserveSequenceNodeComments preserves comments for sequence nodes
func preserveSequenceNodeComments(existingNode, newNode *yaml.Node) {
	// for sequences, preserve comments based on matching "parser_function" field (for parsers)
	// or by array index as a fallback
	existingByParser := make(map[string]*yaml.Node)
	for _, existingItem := range existingNode.Content {
		if existingItem.Kind == yaml.MappingNode {
			parser := findFieldValue(existingItem, "parser_function")
			if parser != "" {
				existingByParser[parser] = existingItem
			}
		}
	}

	// match parsers by parser_function if available
	for i, newItem := range newNode.Content {
		if newItem.Kind == yaml.MappingNode {
			parser := findFieldValue(newItem, "parser_function")
			if parser != "" && existingByParser[parser] != nil {
				existingItem := existingByParser[parser]
				newItem.HeadComment = existingItem.HeadComment
				newItem.LineComment = existingItem.LineComment
				newItem.FootComment = existingItem.FootComment
				preserveFieldComments(existingItem, newItem)
			} else if i < len(existingNode.Content) {
				// fallback to index-based matching
				existingItem := existingNode.Content[i]
				newItem.HeadComment = existingItem.HeadComment
				newItem.LineComment = existingItem.LineComment
				newItem.FootComment = existingItem.FootComment
				preserveFieldComments(existingItem, newItem)
			}
		}
	}
}

// preserveFieldComments recursively preserves comments from an existing node to a new node
func preserveFieldComments(existingNode, newNode *yaml.Node) {
	if existingNode.Kind != newNode.Kind {
		return
	}

	switch newNode.Kind {
	case yaml.MappingNode:
		preserveMappingNodeComments(existingNode, newNode)
	case yaml.SequenceNode:
		preserveSequenceNodeComments(existingNode, newNode)
	}
}

// addCatalogerFieldComment adds appropriate comment to a single cataloger field
func addCatalogerFieldComment(keyNode, valueNode *yaml.Node, catalogerName string) {
	switch keyNode.Value {
	case "ecosystem":
		// ecosystem is MANUAL
		if keyNode.LineComment == "" {
			keyNode.LineComment = "MANUAL"
		}
	case "name", "type":
		// add AUTO-GENERATED comment to these fields
		if keyNode.LineComment == "" {
			keyNode.LineComment = autoGeneratedComment
		}
	case "source":
		// add AUTO-GENERATED comment to source field
		if keyNode.LineComment == "" {
			keyNode.LineComment = autoGeneratedComment
		}
	case "config":
		// add AUTO-GENERATED comment to config field
		if keyNode.LineComment == "" {
			keyNode.LineComment = autoGeneratedComment
		}
	case "selectors":
		// selectors are AUTO-GENERATED
		if keyNode.LineComment == "" {
			keyNode.LineComment = autoGeneratedComment
		}
	case "parsers":
		// parsers is AUTO-GENERATED structure
		if keyNode.LineComment == "" {
			keyNode.LineComment = "AUTO-GENERATED structure"
		}
		addParserComments(valueNode)
	case "detectors":
		// detectors are AUTO-GENERATED for binary-classifier-cataloger, MANUAL for others
		if catalogerName == "binary-classifier-cataloger" {
			keyNode.LineComment = autoGeneratedComment
		} else if keyNode.LineComment == "" {
			keyNode.LineComment = "MANUAL - edit detectors here"
		}
	case "metadata_types":
		// cataloger-level metadata_types (for custom catalogers) are AUTO-GENERATED
		if keyNode.LineComment == "" {
			keyNode.LineComment = autoGeneratedComment
		}
	case "package_types":
		// cataloger-level package_types (for custom catalogers) are AUTO-GENERATED
		if keyNode.LineComment == "" {
			keyNode.LineComment = autoGeneratedComment
		}
	case "json_schema_types":
		// json_schema_types are AUTO-GENERATED
		if keyNode.LineComment == "" {
			keyNode.LineComment = autoGeneratedComment
		}
	case "capabilities":
		// capabilities are MANUAL
		if keyNode.LineComment == "" {
			keyNode.LineComment = "MANUAL - edit capabilities here"
		}
	}
}

func addCatalogerComments(catalogersNode *yaml.Node) {
	// catalogersNode should be a sequence of cataloger entries
	if catalogersNode.Kind != yaml.SequenceNode {
		return
	}

	for _, catalogerNode := range catalogersNode.Content {
		if catalogerNode.Kind != yaml.MappingNode {
			continue
		}

		// get the cataloger name for special handling
		catalogerName := findFieldValue(catalogerNode, "name")

		// iterate through the fields of this cataloger entry
		for i := 0; i < len(catalogerNode.Content); i += 2 {
			keyNode := catalogerNode.Content[i]
			valueNode := catalogerNode.Content[i+1]
			addCatalogerFieldComment(keyNode, valueNode, catalogerName)
		}
	}
}

func addParserComments(parsersNode *yaml.Node) {
	// parsersNode should be a sequence of parser entries
	if parsersNode.Kind != yaml.SequenceNode {
		return
	}

	for _, parserNode := range parsersNode.Content {
		if parserNode.Kind != yaml.MappingNode {
			continue
		}

		// iterate through the fields of this parser entry
		for i := 0; i < len(parserNode.Content); i += 2 {
			keyNode := parserNode.Content[i]
			valueNode := parserNode.Content[i+1]

			switch keyNode.Value {
			case "parser_function", "metadata_types", "package_types", "json_schema_types":
				// add AUTO-GENERATED comment to these fields
				if keyNode.LineComment == "" {
					keyNode.LineComment = autoGeneratedComment
				}
			case "detector":
				// detector is AUTO-GENERATED
				if keyNode.LineComment == "" {
					keyNode.LineComment = autoGeneratedComment
				}
				addDetectorComments(valueNode)
			case "capabilities":
				// capabilities are MANUAL
				if keyNode.LineComment == "" {
					keyNode.LineComment = "MANUAL - preserved across regeneration"
				}
			}
		}
	}
}

func addDetectorComments(detectorNode *yaml.Node) {
	// detectorNode should be a mapping node with method and criteria fields
	if detectorNode.Kind != yaml.MappingNode {
		return
	}

	// iterate through the fields of the detector
	for i := 0; i < len(detectorNode.Content); i += 2 {
		keyNode := detectorNode.Content[i]

		switch keyNode.Value {
		case "method", "criteria":
			// add AUTO-GENERATED comment to these fields
			if keyNode.LineComment == "" {
				keyNode.LineComment = autoGeneratedComment
			}
		}
	}
}