package commandkit

import (
	"bytes"
	"errors"
	"fmt"
	"io"
	"runtime/debug"

	internalcobra "gitea.maximumdirect.net/eric/CommandKit/internal/cobra"
	commandmeta "gitea.maximumdirect.net/eric/CommandKit/internal/commandmeta"
	yaml "go.yaml.in/yaml/v4"
)

const commandKitModulePath = "gitea.maximumdirect.net/eric/CommandKit"

type helpInput struct {
	Targets Supplied[[]string]
}

type versionInput struct {
	Scope  string
	Format string
}

type versionDocument struct {
	Name     string `yaml:"name"`
	Version  string `yaml:"version"`
	Revision string `yaml:"revision"`
}

func (a *App) builtinCommands() []Command {
	help := captureCommand(CommandSpec[helpInput]{
		Name:        "help",
		Summary:     "Show help for commands.",
		Description: "Describe registered commands and their inputs.",
		Arguments: []Argument[helpInput]{RepeatArgument(ArgumentMeta{Name: "COMMAND", Usage: "registered command path"}, 0, -1,
			func(value string) (string, error) { return value, nil },
			func(input *helpInput, value Supplied[[]string]) { input.Targets = value })},
	}, func(current commandExecution, input helpInput) Outcome {
		return current.renderHelpTargets(input.Targets.Value)
	})
	scopeDefault := "app"
	formatDefault := "text"
	version := NewCommand(CommandSpec[versionInput]{
		Name:        "version",
		Summary:     "Show application or CommandKit version.",
		Description: "Report identity and build metadata without loading application configuration.",
		Flags: []Flag[versionInput]{
			ValueFlag(FlagMeta{Name: "scope", Usage: "version subject"}, &scopeDefault, parseVersionScope, func(input *versionInput, value Supplied[string]) { input.Scope = value.Value }),
			ValueFlag(FlagMeta{Name: "format", Usage: "output format"}, &formatDefault, parseVersionFormat, func(input *versionInput, value Supplied[string]) { input.Format = value.Value }),
		},
		Run: func(invocation Invocation, input versionInput) Outcome {
			identity := a.identity
			if input.Scope == "commandkit" {
				identity = commandKitBuildIdentity(readBuildInfo())
			}
			if identity.Version == "" {
				identity.Version = "dev"
			}
			return renderVersionOutcome(identity, input.Format, invocation.Streams)
		},
	})
	return []Command{help, version}
}

func parseVersionScope(value string) (string, error) {
	if value != "app" && value != "commandkit" {
		return "", fmt.Errorf("scope must be app or commandkit, got %q", value)
	}
	return value, nil
}

func parseVersionFormat(value string) (string, error) {
	if value != "text" && value != "yaml" {
		return "", fmt.Errorf("format must be text or yaml, got %q", value)
	}
	return value, nil
}

func (a *App) renderHelpOutcome(path []string, streams Streams) Outcome {
	session := internalcobra.Prepare(a.routeSnapshot().metadata, commandmeta.ParseOptions{})
	return a.renderHelpOutcomeWithSession(path, streams, session)
}

func (a *App) renderHelpTargets(targets []string, streams Streams) Outcome {
	session := internalcobra.Prepare(a.routeSnapshot().metadata, commandmeta.ParseOptions{})
	return a.renderHelpTargetsWithSession(targets, streams, session)
}

func (a *App) renderHelpTargetsWithSession(targets []string, streams Streams, session *internalcobra.Session) Outcome {
	return a.renderHelpOutcomeWithSession(targets, streams, session)
}

func (a *App) renderHelpOutcomeWithSession(path []string, streams Streams, session *internalcobra.Session) Outcome {
	content, failure := session.RenderHelp(path)
	if failure != nil {
		if failure.Usage {
			return Usage(errors.New(failure.Message))
		}
		return Failure(errors.New(failure.Message))
	}
	if err := writeReport(streams.Out, []byte(content)); err != nil {
		return incompleteReport(err)
	}
	return Success()
}

func renderVersionOutcome(identity Identity, format string, streams Streams) Outcome {
	var content []byte
	switch format {
	case "text":
		name := identity.Name
		if identity.Version == "" {
			identity.Version = "dev"
		}
		line := name + " " + identity.Version
		if identity.Revision != "" {
			line += " (" + identity.Revision + ")"
		}
		content = []byte(line + "\n")
	case "yaml":
		if identity.Version == "" {
			identity.Version = "dev"
		}
		var buffer bytes.Buffer
		if err := encodeYAML(&buffer, versionDocument{Name: identity.Name, Version: identity.Version, Revision: identity.Revision}); err != nil {
			return Failure(err)
		}
		content = buffer.Bytes()
	default:
		return Usage(fmt.Errorf("unsupported version format %q", format))
	}
	if err := writeReport(streams.Out, content); err != nil {
		return incompleteReport(err)
	}
	return Success()
}

func encodeYAML(writer io.Writer, document any) error {
	encoder := yaml.NewEncoder(writer)
	encoder.SetIndent(2)
	return encoder.Encode(document)
}

func writeReport(writer io.Writer, content []byte) error {
	checked := &checkedWriter{writer: writer}
	_, err := checked.Write(content)
	if err == nil {
		err = checked.failure
	}
	return err
}

func incompleteReport(err error) Outcome {
	outcome := Failure(err)
	outcome.ReportIncomplete = true
	outcome.DeliveryError = err
	return outcome
}

func readBuildInfo() *debug.BuildInfo {
	info, ok := debug.ReadBuildInfo()
	if !ok {
		return nil
	}
	return info
}

func commandKitBuildIdentity(info *debug.BuildInfo) Identity {
	identity := Identity{Name: "CommandKit", Version: "dev"}
	if info == nil {
		return identity
	}
	var module *debug.Module
	if info.Main.Path == commandKitModulePath {
		module = &info.Main
	} else {
		for _, dependency := range info.Deps {
			if dependency != nil && dependency.Path == commandKitModulePath {
				module = dependency
				break
			}
		}
	}
	if module == nil {
		return identity
	}
	version := module.Version
	if module.Replace != nil {
		version = module.Replace.Version
	}
	if version != "" && version != "(devel)" {
		identity.Version = version
	}
	return identity
}