package engine

import (
	"path"
	"strings"

	"gitea.maximumdirect.net/eric/ConfigKit/internal/document"
)

const directiveKey = "configkit"

func splitImportDirectives(root *document.Node) (*document.Node, []importDeclarationSpec, []Diagnostic) {
	body := document.Clone(root)
	var declarations []importDeclarationSpec
	directiveIndex := -1
	for index, entry := range body.Mapping {
		if entry.Key != directiveKey {
			continue
		}
		directiveIndex = index
		parsed, diagnostics := parseImportSpecificationDirective(entry.Value, Keys(directiveKey))
		if len(diagnostics) != 0 {
			return nil, nil, diagnostics
		}
		declarations = parsed
		break
	}
	if directiveIndex >= 0 {
		body.Mapping = append(body.Mapping[:directiveIndex], body.Mapping[directiveIndex+1:]...)
	}
	if diagnostics := nestedDirectiveDiagnostics(body, Path{}); len(diagnostics) != 0 {
		return nil, nil, diagnostics
	}
	return body, declarations, nil
}

func nestedDirectiveDiagnostics(node *document.Node, current Path) []Diagnostic {
	if node.Kind == document.Mapping {
		for _, entry := range node.Mapping {
			childPath := current.Key(entry.Key)
			if entry.Key == directiveKey {
				location := publicLocation(entry.KeyLocation)
				return []Diagnostic{{Code: CodeImportInvalid, Severity: SeverityError, Path: childPath, Message: "configuration directives are permitted only at the document root", Primary: &location}}
			}
			if diagnostics := nestedDirectiveDiagnostics(entry.Value, childPath); len(diagnostics) != 0 {
				return diagnostics
			}
		}
	} else if node.Kind == document.Sequence {
		for index, child := range node.Sequence {
			if diagnostics := nestedDirectiveDiagnostics(child, current.Index(index)); len(diagnostics) != 0 {
				return diagnostics
			}
		}
	}
	return nil
}

func fragmentVersionClaim(root *document.Node, rule *VersionRule) *document.Node {
	return fragmentVersionClaimProjected(root, rule, -1, nil)
}

func fragmentVersionClaimProjected(root *document.Node, rule *VersionRule, sourceIndex int, ranges []sequenceRange) *document.Node {
	return fragmentVersionClaimWithIndex(root, rule, sourceIndex, indexSequenceRanges(ranges))
}

func fragmentVersionClaimWithIndex(root *document.Node, rule *VersionRule, sourceIndex int, ranges sequenceRangeIndex) *document.Node {
	if rule == nil {
		return nil
	}
	current := root
	currentPath := Path{}
	if len(rule.Path.segments) == 0 {
		return current
	}
	for _, segment := range rule.Path.segments {
		switch current.Kind {
		case document.Mapping:
			if segment.kind == pathSegmentIndex {
				return current
			}
			index := documentEntryIndex(current.Mapping, segment.key)
			if index < 0 {
				return nil
			}
			current = current.Mapping[index].Value
			currentPath = currentPath.Key(segment.key)
		case document.Sequence:
			index, valid := schemaIndex(segment)
			if !valid {
				return current
			}
			if assigned, found := ranges[sequenceRangeKey{sourceIndex: sourceIndex, path: currentPath.String()}]; found {
				if index < assigned.start || index >= assigned.end {
					return nil
				}
				index -= assigned.start
			}
			if index < 0 || index >= len(current.Sequence) {
				return nil
			}
			current = current.Sequence[index]
			currentPath = currentPath.Index(index)
		default:
			// A scalar or null at an ancestor replaces the protected subtree.
			return current
		}
	}
	return current
}

func validImportPath(value string) bool {
	if value == "" || strings.TrimSpace(value) != value || path.IsAbs(value) || strings.HasPrefix(value, "//") {
		return false
	}
	return !hasImportScheme(value)
}

func hasImportScheme(value string) bool {
	colon := strings.IndexByte(value, ':')
	slash := strings.IndexByte(value, '/')
	if colon <= 0 || (slash >= 0 && slash < colon) {
		return false
	}
	for index := 0; index < colon; index++ {
		character := value[index]
		if index == 0 {
			if (character < 'a' || character > 'z') && (character < 'A' || character > 'Z') {
				return false
			}
			continue
		}
		if (character < 'a' || character > 'z') && (character < 'A' || character > 'Z') &&
			(character < '0' || character > '9') && character != '+' && character != '-' && character != '.' {
			return false
		}
	}
	return true
}

func nodeImportDiagnostic(code Code, path Path, message string, node *document.Node) Diagnostic {
	location := publicLocation(node.Location)
	return Diagnostic{Code: code, Severity: SeverityError, Path: path, Message: message, Primary: &location}
}

func overlayDirectiveDiagnostics(node *document.Node, current Path) []Diagnostic {
	if node.Kind == document.Mapping {
		for _, entry := range node.Mapping {
			childPath := current.Key(entry.Key)
			if entry.Key == directiveKey {
				location := publicLocation(entry.KeyLocation)
				return []Diagnostic{{
					Code: CodeOverlayDirective, Severity: SeverityError, Path: childPath,
					Message: "overlays cannot contain configuration directives", Primary: &location,
				}}
			}
			if diagnostics := overlayDirectiveDiagnostics(entry.Value, childPath); len(diagnostics) != 0 {
				return diagnostics
			}
		}
	} else if node.Kind == document.Sequence {
		for index, child := range node.Sequence {
			if diagnostics := overlayDirectiveDiagnostics(child, current.Index(index)); len(diagnostics) != 0 {
				return diagnostics
			}
		}
	}
	return nil
}

func disabledDirectiveDiagnostics(node *document.Node, path Path) []Diagnostic {
	var diagnostics []Diagnostic
	if node.Kind == document.Mapping {
		for _, entry := range node.Mapping {
			childPath := path.Key(entry.Key)
			if entry.Key == directiveKey {
				location := Location{SourceID: entry.KeyLocation.SourceID, Line: entry.KeyLocation.Line, Column: entry.KeyLocation.Column}
				diagnostics = append(diagnostics, Diagnostic{
					Code: CodeImportDisabled, Severity: SeverityError, Path: childPath,
					Message: "configuration directives require imports to be enabled", Primary: &location,
				})
			}
			diagnostics = append(diagnostics, disabledDirectiveDiagnostics(entry.Value, childPath)...)
		}
	} else if node.Kind == document.Sequence {
		for index, child := range node.Sequence {
			diagnostics = append(diagnostics, disabledDirectiveDiagnostics(child, path.Index(index))...)
		}
	}
	return diagnostics
}