package configkit

import (
	"os"
	"reflect"

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

// Definition contains reusable application rules for a configuration type.
// Secret is a pure predicate that can add sensitivity to semantic paths.
// Definitions should be treated as read-only after being shared.
type Definition[T any] struct {
	Defaults func() T
	Resolve  func(*T, *Resolution) error
	Validate func(*T, *Validation)
	Version  *VersionRule
	Secret   func(Path) bool
}

// Options contains the application definition and per-load input selections.
// Imports enables explicit path and glob imports; Profile selects one fixed profile
// overlay; Overrides contains only values explicitly supplied by an application CLI.
type Options[T any] struct {
	Definition Definition[T]
	Imports    bool
	Profile    string
	Filesystem *FilesystemContext
	Overrides  []Override
}

// FilesystemContext supplies filesystem roots for imports and profiles.
type FilesystemContext struct {
	BaseDir string
	Root    string
}

// Override describes one explicitly supplied application override. Value uses
// parser-neutral built-in scalars, nil, []any, or map[string]any; Flag is a safe
// display name and must not contain a raw argument or value.
type Override struct {
	Path  Path
	Value any
	Flag  string
}

// Resolution exposes entry-state input provenance, surviving-input presence, and
// audited application resolution changes. A resolver must not retain or
// concurrently use the context.
type Resolution struct {
	state *resolutionState
}

// VersionRule declares the input path and application checker for a schema version.
// At that path, string and decimal-integer input is supplied as Version.Text.
type VersionRule struct {
	Path  Path
	Check func(Version, *Validation) error
}

// Version preserves the absent, null, and textual states of a schema-version input.
// Text is the exact spelling of accepted string or decimal-integer input.
type Version struct {
	Present bool
	Null    bool
	Text    string
}

// Result is a successful independently owned configuration load.
type Result[T any] struct {
	Config T

	metadata         Metadata
	sources          []SourceInfo
	diagnostics      []Diagnostic
	baseline         *document.Node
	input            *document.Node
	inputOrigins     map[string]Origin
	final            *document.Node
	resolution       []resolutionSnapshot
	applications     []historyApplication
	secrets          map[string]bool
	secretReferences map[string]string
}

// Metadata returns detached effective presence, origin, and history records.
func (r *Result[T]) Metadata() Metadata {
	if r == nil {
		return Metadata{}
	}
	return cloneMetadata(r.metadata)
}

// Sources returns a detached list of sources used by the load.
func (r *Result[T]) Sources() []SourceInfo {
	if r == nil {
		return nil
	}
	return cloneSourceInfos(r.sources)
}

// Diagnostics returns detached nonfatal diagnostics from the load.
func (r *Result[T]) Diagnostics() []Diagnostic {
	if r == nil {
		return nil
	}
	return cloneDiagnostics(r.diagnostics)
}

// Load parses and strictly decodes zero or one selected source, explicitly enabled
// imports, and one selected profile. It accepts at most one Options value and
// returns no result when any error is reported.
func Load[T any](source Source, supplied ...Options[T]) (*Result[T], error) {
	return loadWithSecretLookup(source, os.LookupEnv, supplied...)
}

func loadWithSecretLookup[T any](source Source, lookup secretLookup, supplied ...Options[T]) (*Result[T], error) {
	accumulator := diagnosticAccumulator{}
	options, diagnostics := selectOptions(source, supplied)
	accumulator.add(diagnostics...)
	if len(diagnostics) != 0 {
		return nil, accumulator.loadError()
	}

	input, diagnostics := assembleBaseInput(source, options)
	accumulator.sources = input.sources
	accumulator.add(diagnostics...)
	if len(diagnostics) != 0 {
		return nil, accumulator.loadError()
	}
	schema, schemaIssue := buildSchema(reflect.TypeFor[T]())
	if schemaIssue != nil {
		accumulator.add(diagnosticFromSchemaIssue(schemaIssue))
		return nil, accumulator.loadError()
	}
	versionDiagnostics := checkVersion(options.Definition.Version, input.document)
	accumulator.add(versionDiagnostics...)
	if hasErrors(versionDiagnostics) {
		return nil, accumulator.loadError()
	}
	input, diagnostics = applyInputLayers(source, options, input)
	accumulator.sources = input.sources
	accumulator.add(diagnostics...)
	if len(diagnostics) != 0 {
		return nil, accumulator.loadError()
	}

	decoded, diagnostics := decodeLoadInput(schema, options.Definition, input)
	accumulator.add(diagnostics...)
	if len(diagnostics) != 0 {
		return nil, accumulator.loadError()
	}
	resolved, diagnostics := resolveLoadInput(schema, options.Definition, input, decoded)
	accumulator.add(diagnostics...)
	if hasErrors(diagnostics) {
		return nil, accumulator.loadError()
	}
	if !historyNodesWithinLimit(decoded.baseline, decoded.final, resolved.final, resolved.applications, resolved.snapshots) {
		accumulator.add(Diagnostic{Code: CodeExplainLimitExceeded, Severity: SeverityError, Message: "retained configuration history exceeds the node limit"})
		return nil, accumulator.loadError()
	}

	// Detach resolver-borrowed values before reference mutation or validation.
	configuration, ownershipIssue := detachLoadConfiguration(schema, resolved.configuration, cloneUnresolvedSecrets)
	if ownershipIssue != nil {
		accumulator.add(*ownershipIssue)
		return nil, accumulator.loadError()
	}
	secretResolution := resolveSecretReferences(reflect.ValueOf(&configuration).Elem(), schema, input.document, lookup)
	accumulator.add(secretResolution.diagnostics...)
	if hasErrors(secretResolution.diagnostics) {
		return nil, accumulator.loadError()
	}
	if options.Definition.Validate != nil {
		diagnostics = runValidation(&configuration, options.Definition.Validate, schema, resolved.final, input.document, secretResolution.lookups)
		accumulator.add(diagnostics...)
		if hasErrors(diagnostics) {
			return nil, accumulator.loadError()
		}
	}
	resolved.configuration = configuration
	// Publication detaches equal-valued validator replacements, preserving the
	// validated secret state, then finalizes metadata and sensitivity.
	return publishLoadResult(schema, options.Definition, resolved, secretResolution.references, &accumulator)
}