package wand

import (
	"fmt"
	"github.com/iancoleman/strcase"
	"io"
	"sort"
	"strings"
)

func formatHelp(w io.Writer, doc doc) error {
	var err error
	println := func(a ...any) {
		if err != nil {
			return
		}

		_, err = fmt.Fprintln(w, a...)
	}

	printf := func(f string, a ...any) {
		if err != nil {
			return
		}

		_, err = fmt.Fprintf(w, f, a...)
	}

	printf(doc.fullCommand)
	println()
	if doc.hasImplementation || doc.synopsis.hasSubcommands {
		println()
		printf("Synopsis")
		println()
	}

	if doc.hasImplementation {
		println()
		printf(doc.synopsis.command)
		if doc.synopsis.hasOptions {
			printf(" [options ...]")
		}

		for _, n := range doc.synopsis.arguments.names {
			printf(" %s", n)
		}

		if doc.synopsis.arguments.variadic {
			printf("...")
			if doc.synopsis.arguments.minPositional > 0 {
				printf(" min %d arguments", doc.synopsis.arguments.minPositional)
			}

			if doc.synopsis.arguments.maxPositional > 0 {
				printf(" max %d arguments", doc.synopsis.arguments.maxPositional)
			}
		}

		println()
	}

	if doc.synopsis.hasSubcommands {
		if !doc.hasImplementation {
			println()
		}

		printf("%s <subcommand> [options or args...]", doc.synopsis.command)
		println()
		println()
		printf("(For the details about the available subcommands, see the according section below.)")
		println()
	}

	if len(doc.description) > 0 {
		println()
		printf(paragraphs(doc.description))
		println()
	}

	if len(doc.options) > 0 {
		println()
		printf("Options")
		println()
		println()
		printf("[*]: accepts multiple instances of the same option")
		println()
		printf("[b]: booelan flag, true or false, or no argument means true")
		println()
		println()

		var names []string
		od := make(map[string]string)
		for _, o := range doc.options {
			ons := []string{fmt.Sprintf("--%s", o.name)}
			for _, sn := range o.shortNames {
				ons = append(ons, fmt.Sprintf("-%s", sn))
			}

			n := strings.Join(ons, ", ")
			if o.acceptsMultiple {
				n = fmt.Sprintf("%s [*]", n)
			}

			if o.isBool {
				n = fmt.Sprintf("%s [b]", n)
			}

			names = append(names, n)
			od[n] = o.description
		}

		sort.Strings(names)

		var max int
		for _, n := range names {
			if len(n) > max {
				max = len(n)
			}
		}

		for i := range names {
			pad := strings.Join(make([]string, max-len(names[i])+1), " ")
			names[i] = fmt.Sprintf("%s%s", names[i], pad)
		}

		for _, n := range names {
			printf(n)
			if od[n] != "" {
				printf(": %s", paragraphs(od[n]))
			}

			println()
		}
	}

	if len(doc.subcommands) > 0 {
		println()
		printf("Subcommands")
		println()
		println()

		var names []string
		cd := make(map[string]string)
		for _, sc := range doc.subcommands {
			name := sc.name
			if sc.isDefault {
				name = fmt.Sprintf("%s (default)", name)
			}

			d := sc.description
			if sc.isHelp {
				d = fmt.Sprintf("Show this help. %s", d)
			}

			if sc.hasHelpSubcommand {
				d = fmt.Sprintf("%s - For help, see: %s %s help", d, doc.name, sc.name)
			} else if sc.hasHelpOption {
				d = fmt.Sprintf("%s - For help, see: %s %s --help", d, doc.name, sc.name)
			}

			cd[name] = d
		}

		sort.Strings(names)

		var max int
		for _, n := range names {
			if len(n) > max {
				max = len(n)
			}
		}

		for i := range names {
			pad := strings.Join(make([]string, max-len(names[i])+1), " ")
			names[i] = fmt.Sprintf("%s%s", names[i], pad)
		}

		for _, n := range names {
			printf(n)
			if cd[n] != "" {
				printf(": %s", paragraphs(cd[n]))
			}

			println()
		}
	}

	if len(doc.options) > 0 {
		printf(paragraphs(envDocs))
		println()
		println()
		o := doc.options[0]
		printf("Example environment variable:")
		println()
		println()
		printf(strcase.ToSnake(o.name))
		printf("=")
		if o.isBool {
			printf("true")
		} else {
			printf("42")
		}

		println()
	}

	if len(doc.options) > 0 && len(doc.configFiles) > 0 {
		printf(paragraphs(configDocs))
		println()
		println()
		printf("Config files:")
		println()
		println()
		for _, cf := range doc.configFiles {
			if cf.fromOption {
				printf("zero or more configuration files defined by the --config option")
				println()
				continue
			}

			if cf.fn != "" {
				printf(cf.fn)
				if cf.optional {
					printf(" (optional)")
				}

				println()
				continue
			}
		}

		println()
		o := doc.options[0]
		printf("Example configuration entry:")
		println()
		println()
		printf("# default for --")
		printf(o.name)
		println()
		printf(strcase.ToSnake(o.name))
		printf(" = ")
		if o.isBool {
			printf("true")
		} else {
			printf("42")
		}

		println()
	}

	return err
}