package cmd

import (
	"flag"
	"fmt"
	"os"
	"regexp"
	"strconv"
	"strings"

	"git.noodles.cam/claude-skills/marketplace/cli/internal/issue"
)

var numberRe = regexp.MustCompile(`^\d+$`)

func init() {
	register(&Command{
		Name:  "ac",
		Group: GroupIssue,
		Args:  "<id>",
		Short: "list and tick an issue's checkboxes",
		Long: `A checkbox is the one part of a body that is *state* and not prose. Everything
else is written once; boxes get ticked as the work goes, and the only other ways
to tick one are a human with an editor or a model rewriting the whole body — the
second worse than the first, because the rewrite re-flows the text and the
issue's diff swells around a change of one character. This changes that one
character and nothing else.

Named after ` + "`## Acceptance criteria`" + `, where most boxes live, but every checkbox in
the body is listed and tickable: a type/feature keeps its children under
` + "`## Issues`" + `, and binding this to one heading would silently lose half of them.

A substring picks an item only when it picks exactly one. Two matches is an
error listing both — a coin flip would tick the wrong box and look like it
worked.

Delivering the changed body to a tracker is not part of this; that is
` + "`kettle push --update`" + `.`,
		Examples: []Example{
			{"kettle ac wire-sqlc-appclick", "numbered list with state"},
			{"kettle ac wire-sqlc-appclick --check 3", "tick by number"},
			{"kettle ac wire-sqlc-appclick --check регресс", "tick by substring"},
			{"kettle ac wire-sqlc-appclick --uncheck 3", "untick it again"},
		},
		Setup: func(fs *flag.FlagSet) func([]string) error {
			check := fs.String("check", "", "tick one item: number or substring")
			uncheck := fs.String("uncheck", "", "untick one item: number or substring")
			out := storeFlag(fs)

			return func(args []string) error {
				if len(args) != 1 {
					return Fail("give exactly one issue id")
				}
				checking, unchecking := wasSet(fs, "check"), wasSet(fs, "uncheck")
				if checking && unchecking {
					return Fail("--check and --uncheck are mutually exclusive")
				}
				id := args[0]
				root, err := storeRoot(*out)
				if err != nil {
					return err
				}
				path := issue.PathOf(root, id)
				// Raw bytes in and raw bytes out: byte-for-byte means the line
				// endings too. Reading a CRLF file with translation and writing
				// it back would rewrite every line while claiming to have
				// changed one character.
				raw, err := os.ReadFile(path)
				if err != nil {
					return Fail("no issue %q in %s", id, root)
				}
				text := string(raw)

				// The whole file, not just the body: line numbers then point at
				// the file, and the metadata block is rewritten by nobody.
				// Round-tripping through the parser would re-render metadata and
				// re-strip the body, which is exactly the churn this avoids.
				items := issue.Checkboxes(text)
				needle, checked := *check, true
				if unchecking {
					needle, checked = *uncheck, false
				}
				selecting := checking || unchecking

				if len(items) == 0 {
					if selecting {
						return Fail("%s has no checkboxes", id)
					}
					fmt.Printf("%s — no checkboxes\n", id)
					return nil
				}

				if !selecting {
					done, total := issue.CheckboxProgress(text)
					fmt.Printf("%s — %d/%d   %s\n", id, done, total, path)
					fmt.Println(strings.Join(listing(items), "\n"))
					return nil
				}

				item, err := selectItem(items, needle)
				if err != nil {
					return err
				}
				updated, err := issue.SetCheckbox(text, item.Line, checked)
				if err != nil {
					return err
				}
				if updated == text {
					fmt.Printf("unchanged  %2d %s %s\n", item.Index, box(item.Checked), item.Text)
					return nil
				}
				if err := os.WriteFile(path, []byte(updated), 0o644); err != nil {
					return err
				}
				if _, _, err := issue.BuildIndex(root); err != nil {
					return err
				}

				verb := "checked"
				if !checked {
					verb = "unchecked"
				}
				done, total := issue.CheckboxProgress(updated)
				fmt.Printf("%s   %2d %s %s\n", verb, item.Index, box(checked), item.Text)
				fmt.Printf("%s — %d/%d   %s:%d\n", id, done, total, path, item.Line)
				return nil
			}
		},
	})
}

func box(checked bool) string {
	if checked {
		return "[x]"
	}
	return "[ ]"
}

// listing is the numbered list, grouped by the heading each item sits under.
func listing(items []issue.Checkbox) []string {
	var out []string
	section := "\x00" // no heading can equal this, so the first item opens a group
	for _, c := range items {
		if c.Section != section {
			section = c.Section
			head := section
			if head == "" {
				head = "(above the first heading)"
			}
			out = append(out, "", head)
		}
		out = append(out, fmt.Sprintf("  %2d %s %s", c.Index, box(c.Checked), c.Text))
	}
	return out
}

// selectItem resolves a --check/--uncheck argument to exactly one item.
func selectItem(items []issue.Checkbox, needle string) (issue.Checkbox, error) {
	needle = strings.TrimSpace(needle)
	if needle == "" {
		return issue.Checkbox{}, Fail("empty selector — give an item number or a substring")
	}
	if numberRe.MatchString(needle) {
		n, _ := strconv.Atoi(needle)
		if n < 1 || n > len(items) {
			return issue.Checkbox{}, Fail("no item %d — the issue has %d", n, len(items))
		}
		return items[n-1], nil
	}
	var hits []issue.Checkbox
	for _, c := range items {
		if strings.Contains(strings.ToLower(c.Text), strings.ToLower(needle)) {
			hits = append(hits, c)
		}
	}
	switch len(hits) {
	case 0:
		return issue.Checkbox{}, Fail("nothing matches %q", needle)
	case 1:
		return hits[0], nil
	}
	lines := []string{fmt.Sprintf("%q matches %d items — narrow it down, or use a number:", needle, len(hits))}
	for _, c := range hits {
		lines = append(lines, fmt.Sprintf("  %2d %s %s", c.Index, box(c.Checked), c.Text))
	}
	return issue.Checkbox{}, Fail("%s", strings.Join(lines, "\n"))
}