// Package cobra adapts CommandKit's neutral command declarations to Cobra and
// pflag. Backend types and failures remain inside this package.
package cobra

import (
	"context"
	"fmt"
	"io"
	"strconv"
	"strings"

	spfcobra "github.com/spf13/cobra"
	"github.com/spf13/pflag"
)

// Command describes one node in a per-parse command tree.
type Command struct {
	Name        string
	Summary     string
	Description string
	Runnable    bool
	Flags       []Flag
	Children    []*Command
}

// Flag describes one local option without exposing a pflag value.
type Flag struct {
	Name     string
	Short    string
	Usage    string
	Default  string
	Boolean  bool
	Repeated bool
	Required bool
}

// Failure is a backend-owned parse failure translated to neutral message data.
type Failure struct {
	Message string
}

// Result contains the selected command and raw input collected by pflag.
type Result struct {
	Path          []string
	HelpRequested bool
	FlagValues    [][]string
	Operands      []string
	Failure       *Failure
}

// ParseOptions makes the parser's context and streams explicit. Nil writers
// are replaced with io.Discard.
type ParseOptions struct {
	Context context.Context
	In      io.Reader
	Out     io.Writer
	Err     io.Writer
}

// Parse constructs a fresh Cobra tree and parses one argv. It routes only the
// leading command words, stopping permanently at the first option or --.
func Parse(root *Command, argv []string, options ParseOptions) Result {
	result := Result{}
	if root == nil {
		return failure(result, "command tree is nil")
	}
	options = normalizeOptions(options)
	backendRoot, nodes := buildTree(root, options)
	leading, tail := splitRoutingPrefix(argv)
	selected, unconsumed, err := backendRoot.Find(leading)
	if err != nil {
		return failure(result, err.Error())
	}
	if selected == nil {
		return failure(result, "no command was selected")
	}
	selectedNode := declarationFor(nodes, selected)
	if selectedNode == nil {
		return failure(result, "selected command is not part of the declared tree")
	}
	result.Path = pathFor(root, selectedNode)

	remaining := append(append([]string(nil), unconsumed...), tail...)
	if err := selected.ParseFlags(remaining); err != nil {
		return failure(result, err.Error())
	}
	operands := selected.Flags().Args()

	result.Operands = append([]string(nil), operands...)
	result.FlagValues = make([][]string, len(selectedNode.Flags))
	for index, flag := range selectedNode.Flags {
		if value := selected.Flags().Lookup(flag.Name); value != nil {
			result.FlagValues[index] = value.Value.(*rawValue).valuesCopy()
		}
	}
	if helpFlag := selected.Flags().Lookup("help"); helpFlag != nil {
		helpRequested, err := helpFlag.Value.(*rawValue).lastBool()
		if err != nil {
			return failure(result, err.Error())
		}
		result.HelpRequested = helpRequested
	}
	if !selectedNode.Runnable && len(result.Operands) > 0 {
		return failure(result, "unknown command or unexpected group operands: "+strings.Join(result.Operands, " "))
	}
	return result
}

func normalizeOptions(options ParseOptions) ParseOptions {
	if options.Context == nil {
		options.Context = context.Background()
	}
	if options.In == nil {
		options.In = strings.NewReader("")
	}
	if options.Out == nil {
		options.Out = io.Discard
	}
	if options.Err == nil {
		options.Err = io.Discard
	}
	return options
}

func buildTree(root *Command, options ParseOptions) (*spfcobra.Command, map[*Command]*spfcobra.Command) {
	nodes := make(map[*Command]*spfcobra.Command)
	var build func(*Command) *spfcobra.Command
	build = func(declaration *Command) *spfcobra.Command {
		backend := &spfcobra.Command{
			Use:                declaration.Name,
			Short:              declaration.Summary,
			Long:               declaration.Description,
			Args:               func(*spfcobra.Command, []string) error { return nil },
			SilenceErrors:      true,
			SilenceUsage:       true,
			DisableSuggestions: true,
		}
		backend.SetContext(options.Context)
		backend.SetIn(options.In)
		backend.SetOut(options.Out)
		backend.SetErr(options.Err)
		backend.SetHelpFunc(func(*spfcobra.Command, []string) {})
		backend.SetUsageFunc(func(*spfcobra.Command) error { return nil })
		backend.SetFlagErrorFunc(func(_ *spfcobra.Command, err error) error { return err })
		backend.Flags().SetInterspersed(true)
		backend.Flags().SortFlags = false
		backend.DisableAutoGenTag = true
		helpValue := &rawValue{boolean: true}
		backend.Flags().VarP(helpValue, "help", "h", "help for this command")
		backend.Flags().Lookup("help").NoOptDefVal = "true"
		for _, declarationFlag := range declaration.Flags {
			value := &rawValue{boolean: declarationFlag.Boolean}
			backend.Flags().VarP(value, declarationFlag.Name, declarationFlag.Short, declarationFlag.Usage)
			backendFlag := backend.Flags().Lookup(declarationFlag.Name)
			backendFlag.DefValue = declarationFlag.Default
			if declarationFlag.Boolean {
				backendFlag.NoOptDefVal = "true"
			}
		}
		// Cobra's automatic help flag is suppressed because CommandKit declares
		// and interprets the local help flag itself.
		backend.SetHelpCommand(nil)
		nodes[declaration] = backend
		for _, child := range declaration.Children {
			backend.AddCommand(build(child))
		}
		return backend
	}
	return build(root), nodes
}

func declarationFor(nodes map[*Command]*spfcobra.Command, selected *spfcobra.Command) *Command {
	for declaration, backend := range nodes {
		if backend == selected {
			return declaration
		}
	}
	return nil
}

func splitRoutingPrefix(argv []string) ([]string, []string) {
	for index, argument := range argv {
		if argument == "--" || (strings.HasPrefix(argument, "-") && argument != "-") {
			return append([]string(nil), argv[:index]...), append([]string(nil), argv[index:]...)
		}
	}
	return append([]string(nil), argv...), nil
}

func pathFor(root, selected *Command) []string {
	var reverse []string
	for current := selected; current != nil && current != root; {
		reverse = append(reverse, current.Name)
		current = parentOf(root, current)
	}
	path := make([]string, len(reverse))
	for index := range reverse {
		path[len(reverse)-index-1] = reverse[index]
	}
	return path
}

func parentOf(root, target *Command) *Command {
	for _, child := range root.Children {
		if child == target {
			return root
		}
		if parent := parentOf(child, target); parent != nil {
			return parent
		}
	}
	return nil
}

func failure(result Result, message string) Result {
	result.Failure = &Failure{Message: message}
	return result
}

type rawValue struct {
	values  []string
	boolean bool
}

func (v *rawValue) Set(value string) error {
	v.values = append(v.values, value)
	return nil
}

func (v *rawValue) String() string {
	if len(v.values) > 0 {
		return v.values[len(v.values)-1]
	}
	return ""
}

func (v *rawValue) Type() string {
	if v.boolean {
		return "bool"
	}
	return "string"
}

func (v *rawValue) IsBoolFlag() bool { return v.boolean }

func (v *rawValue) valuesCopy() []string { return append([]string(nil), v.values...) }

func (v *rawValue) lastBool() (bool, error) {
	var value bool
	for _, raw := range v.values {
		parsed, err := strconv.ParseBool(raw)
		if err != nil {
			return false, fmt.Errorf("invalid boolean value %q for --help", raw)
		}
		value = parsed
	}
	return value, nil
}

var _ pflag.Value = (*rawValue)(nil)