package ckconfig

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"io"
	"sort"
	"strings"

	commandkit "gitea.maximumdirect.net/eric/CommandKit"
	configkit "gitea.maximumdirect.net/eric/ConfigKit"
)

type scopeMetadata struct {
	Name       string      `yaml:"name"`
	Operations []Operation `yaml:"operations"`
}

type scopeInventory struct {
	Scopes []scopeMetadata `yaml:"scopes"`
}

type preparedScope[I, S any] struct {
	scope    Scope[I, S]
	bindings []commandkit.Flag[I]
}

type preparedSuite[I, S any] struct {
	newInput            func() I
	newState            func() S
	checkInput          func(string, Selection, I) error
	scopes              []*preparedScope[I, S]
	byName              map[string]*preparedScope[I, S]
	bindingsByOperation map[Operation][]commandkit.Flag[I]
	scopeChoices        string
	operations          []Operation
	inventory           scopeInventory
	issues              []error
}

// Command eagerly captures a configuration suite as a root-only config family.
// It copies suite slices, retains callback references, and returns a reusable
// declaration; installation does not invoke factories or providers. During an
// inspection, it initializes input separately for each selected scope. A
// comparison initializes and checks both sides before creating shared state
// and calling the pair provider. Suite documents factory timing, zero values,
// shared state, and caller ownership of returned objects.
func Command[I, S any](suite Suite[I, S]) commandkit.Command {
	prepared := captureSuite(suite)
	if len(prepared.scopes) == 0 {
		prepared.issues = append(prepared.issues, errors.New("configuration suite must declare at least one named scope"))
		return commandkit.WithError(commandkit.NoCommand(), errors.Join(prepared.issues...))
	}

	children := make([]commandkit.Command, 0, len(prepared.operations)+1)
	for _, operation := range prepared.operations {
		children = append(children, newConfigOperationCommand(prepared, operation))
	}
	children = append(children, newConfigScopesCommand(prepared))
	declaration := commandkit.RootGroup("config", "Inspect configuration.", children...)
	if len(prepared.issues) > 0 {
		declaration = commandkit.WithError(declaration, errors.Join(prepared.issues...))
	}
	return declaration
}

// AppCommand builds the state-free, input-free convenience suite for application
// configuration. The application consumer supplies only its ConfigKit loader,
// which runs for ordinary operations and separately for each reached comparison
// side after input preflight.
func AppCommand[T any](load func(context.Context, Selection) (*configkit.Result[T], error)) commandkit.Command {
	var adapterLoad func(context.Context, Selection, struct{}, struct{}) (*configkit.Result[T], error)
	if load != nil {
		adapterLoad = func(ctx context.Context, selection Selection, _ struct{}, _ struct{}) (*configkit.Result[T], error) {
			return load(ctx, selection)
		}
	}
	adapted := FromConfigKit[struct{}, struct{}, T]("app", "Application configuration.", adapterLoad)
	return Command(Suite[struct{}, struct{}]{Scopes: []Scope[struct{}, struct{}]{adapted}})
}

func captureSuite[I, S any](suite Suite[I, S]) *preparedSuite[I, S] {
	prepared := &preparedSuite[I, S]{
		newInput:            suite.NewInput,
		newState:            suite.NewState,
		checkInput:          suite.CheckInput,
		byName:              make(map[string]*preparedScope[I, S], len(suite.Scopes)),
		bindingsByOperation: make(map[Operation][]commandkit.Flag[I]),
	}
	selectors := make([]Selector[I], len(suite.Selectors))
	for index, selector := range suite.Selectors {
		selector.Scopes = append([]string(nil), selector.Scopes...)
		selectors[index] = selector
	}

	seenNames := make(map[string]struct{}, len(suite.Scopes))
	for _, original := range suite.Scopes {
		scope := original
		scope.Operations = normalizeOperations(scope.Operations, &prepared.issues, scope.Name)
		scope.issues = append([]error(nil), original.issues...)
		if scope.Name == "" {
			prepared.issues = append(prepared.issues, errors.New("configuration scope name must not be empty"))
		}
		if scope.Name == "all" {
			prepared.issues = append(prepared.issues, fmt.Errorf("configuration scope name %q is reserved", scope.Name))
		}
		if _, exists := seenNames[scope.Name]; exists {
			prepared.issues = append(prepared.issues, fmt.Errorf("duplicate configuration scope %q", scope.Name))
		} else {
			seenNames[scope.Name] = struct{}{}
		}
		for _, issue := range scope.issues {
			prepared.issues = append(prepared.issues, fmt.Errorf("configuration scope %q: %w", scope.Name, issue))
		}
		requiresAcquire, requiresCompare := false, false
		for _, operation := range scope.Operations {
			if operation == Diff {
				requiresCompare = true
			} else {
				requiresAcquire = true
			}
		}
		if requiresAcquire && scope.Acquire == nil {
			prepared.issues = append(prepared.issues, fmt.Errorf("configuration scope %q declares operations without an acquisition callback", scope.Name))
		}
		if requiresCompare && scope.Compare == nil {
			prepared.issues = append(prepared.issues, fmt.Errorf("configuration scope %q declares diff without a comparison callback", scope.Name))
		}
		prepared.scopes = append(prepared.scopes, &preparedScope[I, S]{scope: scope})
	}
	sort.SliceStable(prepared.scopes, func(i, j int) bool {
		return scopeOrder(prepared.scopes[i].scope.Name) < scopeOrder(prepared.scopes[j].scope.Name)
	})
	names := make([]string, 0, len(prepared.scopes))
	for _, scope := range prepared.scopes {
		prepared.byName[scope.scope.Name] = scope
		names = append(names, scope.scope.Name)
	}
	prepared.scopeChoices = joinNames(names)

	for index, selector := range selectors {
		seen := make(map[string]struct{}, len(selector.Scopes))
		uniqueScopes := make([]string, 0, len(selector.Scopes))
		for _, name := range selector.Scopes {
			if _, exists := seenNames[name]; !exists {
				prepared.issues = append(prepared.issues, fmt.Errorf("configuration selector %d references unknown scope %q", index, name))
			}
			if _, exists := seen[name]; exists {
				continue
			}
			seen[name] = struct{}{}
			uniqueScopes = append(uniqueScopes, name)
		}
		selectors[index].Scopes = uniqueScopes
		if len(selector.Scopes) == 0 {
			for scopeIndex := range prepared.scopes {
				if len(prepared.scopes[scopeIndex].scope.Operations) > 0 {
					prepared.scopes[scopeIndex].bindings = append(prepared.scopes[scopeIndex].bindings, selector.Binding)
				}
			}
		} else {
			for _, name := range uniqueScopes {
				if scope, exists := prepared.byName[name]; exists && len(scope.scope.Operations) > 0 {
					scope.bindings = append(scope.bindings, selector.Binding)
				}
			}
		}
	}

	for _, operation := range []Operation{Validate, Show, Sources, Explain, Diff} {
		for _, scope := range prepared.scopes {
			if containsOperation(scope.scope.Operations, operation) {
				prepared.operations = append(prepared.operations, operation)
				break
			}
		}
		for _, selector := range selectors {
			for _, scope := range prepared.scopes {
				if containsOperation(scope.scope.Operations, operation) && selectorApplies(selector.Scopes, scope.scope.Name) {
					prepared.bindingsByOperation[operation] = append(prepared.bindingsByOperation[operation], selector.Binding)
					break
				}
			}
		}
	}
	for _, scope := range prepared.scopes {
		prepared.inventory.Scopes = append(prepared.inventory.Scopes, scopeMetadata{
			Name:       scope.scope.Name,
			Operations: append([]Operation(nil), scope.scope.Operations...),
		})
	}
	return prepared
}

func normalizeOperations(operations []Operation, issues *[]error, scope string) []Operation {
	seen := make(map[Operation]struct{}, len(operations))
	for _, operation := range operations {
		switch operation {
		case Validate, Show, Sources, Explain, Diff:
		default:
			*issues = append(*issues, fmt.Errorf("configuration scope %q declares unknown operation %q", scope, operation))
		}
		seen[operation] = struct{}{}
	}
	ordered := make([]Operation, 0, len(seen))
	for _, operation := range []Operation{Validate, Show, Sources, Explain, Diff} {
		if _, exists := seen[operation]; exists {
			ordered = append(ordered, operation)
		}
	}
	return ordered
}

func scopeOrder(name string) string {
	switch name {
	case "app":
		return "\x00"
	case "promptkit":
		return "\x01"
	default:
		return "\x02" + name
	}
}

func containsOperation(operations []Operation, requested Operation) bool {
	for _, operation := range operations {
		if operation == requested {
			return true
		}
	}
	return false
}

func selectorApplies(scopes []string, name string) bool {
	if len(scopes) == 0 {
		return true
	}
	for _, scope := range scopes {
		if scope == name {
			return true
		}
	}
	return false
}

func joinNames(names []string) string {
	ordered := append([]string(nil), names...)
	sort.Strings(ordered)
	if len(ordered) == 0 {
		return "none"
	}
	return strings.Join(ordered, ", ")
}

func newConfigScopesCommand[I, S any](prepared *preparedSuite[I, S]) commandkit.Command {
	formatDefault := "text"
	spec := commandkit.CommandSpec[scopeInventoryInput]{
		Name:    "scopes",
		Summary: "List configuration scopes and supported operations.",
		Flags: []commandkit.Flag[scopeInventoryInput]{commandkit.ValueFlag(
			commandkit.FlagMeta{Name: "format", Usage: "Output format: text or yaml."}, &formatDefault, parseConfigString,
			func(input *scopeInventoryInput, value commandkit.Supplied[string]) { input.Format = value.Value },
		)},
		CheckInput: func(input scopeInventoryInput) error { return checkConfigFormat(input.Format) },
		Run: func(invocation commandkit.Invocation, input scopeInventoryInput) commandkit.Outcome {
			_ = invocation.Reporter().RenderOutput(func(writer io.Writer) error {
				var report bytes.Buffer
				if input.Format == "yaml" {
					if err := encodeYAML(&report, prepared.inventory); err != nil {
						return err
					}
				} else {
					_, _ = report.WriteString(formatScopeInventory(prepared.inventory))
				}
				_, err := writer.Write(report.Bytes())
				return err
			})
			return commandkit.Success()
		},
	}
	return commandkit.NewCommand(spec)
}

type scopeInventoryInput struct{ Format string }

type scopeInventoryYAML struct {
	Scopes []scopeMetadata `yaml:"scopes"`
}

func formatScopeInventory(inventory scopeInventory) string {
	var output strings.Builder
	for _, scope := range inventory.Scopes {
		output.WriteString(scope.Name)
		output.WriteString(": ")
		for index, operation := range scope.Operations {
			if index > 0 {
				output.WriteString(", ")
			}
			output.WriteString(string(operation))
		}
		output.WriteByte('\n')
	}
	return output.String()
}

func checkConfigFormat(format string) error {
	if format != "text" && format != "yaml" {
		return fmt.Errorf("unsupported configuration format %q", format)
	}
	return nil
}

func parseConfigString(value string) (string, error) { return value, nil }