// SPDX-License-Identifier: GPL-3.0-or-later

package main

import (
	"context"
	"fmt"
	"io"
	"os"
	"sort"
	"strings"
	"unicode/utf8"

	"krino/internal/engine"
	"krino/internal/scan"
	"krino/internal/xdg"
)

// cmdSort plans and applies the included directories. Only -n (dry run) is
// implemented; applying arrives in plan 3.
func cmdSort(g *globals, names []string, stdout, stderr io.Writer) int {
	if g.yes && g.dry {
		return usageError(stderr, "-y and -n cannot be used together")
	}
	if g.json {
		fmt.Fprintln(stderr, "krino: --json is not implemented yet")
		return 2
	}
	if !g.dry {
		fmt.Fprintln(stderr, "krino: applying files is not implemented yet; use -n to see what would happen")
		return 2
	}

	e, errs := engine.Load(mainFile(g), names...)
	if len(errs) > 0 {
		printDiags(stderr, errs)
		return 2
	}

	exit := 0
	printed := false
	for _, d := range e.Dirs {
		if fi, err := os.Stat(d.Root); err != nil || !fi.IsDir() {
			fmt.Fprintf(stderr, "krino: skipping %s: %s is not a directory\n", d.Name, xdg.Abbrev(d.Root))
			exit = 1
			continue
		}
		r, err := e.Match(context.Background(), d)
		if err != nil {
			fmt.Fprintf(stderr, "krino: skipping %s: %v\n", d.Name, err)
			exit = 1
			continue
		}
		if printed {
			fmt.Fprintln(stdout)
		}
		printed = true
		fmt.Fprintf(stdout, "krino: %s  %s\n", d.Name, xdg.Abbrev(d.Root))
		// C3: directory-level warnings go to stderr after the header
		// line above, not before it, so on a terminal they read as
		// describing the directory just named instead of floating above it.
		for _, w := range r.Warnings {
			fmt.Fprintf(stderr, "krino: %s: %s\n", d.Name, w)
		}
		printResult(stdout, r, g.verbose)
	}
	return exit
}

// printResult renders one directory's match result the way krino -n shows
// it, below the header line cmdSort has already written: a summary line,
// then the matched, warnings and skip-count sections, each present only
// when it has something to show. Plan 3 reuses this for the outcome of an
// actual run.
func printResult(w io.Writer, r *engine.Result, verbose bool) {
	// C1: spec §8.2's worked example is "266 scanned" against "41 to act
	// on" and "not acted on: 3 busy · 12 ignored · 210 unmatched", and
	// 41+3+12+210 = 266 - so scanned counts matched, unmatched and skipped
	// alike, not just matched plus unmatched.
	scanned := len(r.Matched) + len(r.Unmatched) + len(r.Skipped)
	warned := 0
	for _, fm := range r.Matched {
		if len(fm.Warnings) > 0 {
			warned++
		}
	}
	for _, fm := range r.Unmatched {
		if len(fm.Warnings) > 0 {
			warned++
		}
	}
	fmt.Fprintf(w, "%d scanned · %d matched · %d warnings · %.2fs\n", scanned, len(r.Matched), warned, r.Elapsed.Seconds())

	if len(r.Matched) > 0 {
		fmt.Fprintln(w)
		printMatched(w, r.Matched)
	}

	if lines := collectWarnings(r); len(lines) > 0 {
		fmt.Fprintln(w)
		fmt.Fprintln(w, "warnings")
		printWarnings(w, lines)
	}

	if line := skipSummaryLine(r, verbose); line != "" {
		fmt.Fprintln(w)
		fmt.Fprintln(w, line)
	}

	if verbose {
		if len(r.Unmatched) > 0 {
			fmt.Fprintln(w)
			fmt.Fprintln(w, "not matched")
			for _, fm := range r.Unmatched {
				fmt.Fprintf(w, "  %s\n", fm.File.Rel)
			}
		}
		if len(r.Skipped) > 0 {
			fmt.Fprintln(w)
			fmt.Fprintln(w, "skipped")
			printSkipped(w, r.Skipped)
		}
	}
}

// printMatched lists each matched file, its Rel padded to the widest shown
// (capped at 40), then each matching rule as "name: reasons", rules joined
// by "; ".
func printMatched(w io.Writer, matched []engine.FileMatch) {
	rels := make([]string, len(matched))
	for i, fm := range matched {
		rels[i] = fm.File.Rel
	}
	width := relWidth(rels)
	for _, fm := range matched {
		parts := make([]string, len(fm.Rules))
		for i, rm := range fm.Rules {
			parts[i] = rm.Rule.Name + ": " + strings.Join(rm.Reasons, ", ")
		}
		fmt.Fprintf(w, "  %s  %s\n", padCell(fm.File.Rel, width), strings.Join(parts, "; "))
	}
}

// warnLine is one file's warning, for the warnings section.
type warnLine struct {
	rel  string
	text string
}

// collectWarnings gathers every file's warnings into a single list sorted
// by Rel across matched and unmatched files alike: a reader scans this
// section by file name and has no way to tell which group a file fell
// into, so grouping by match state is invisible structure that would only
// show up as an odd order. A file's own warnings (when it has more than
// one) stay in the order they were recorded.
func collectWarnings(r *engine.Result) []warnLine {
	files := make([]engine.FileMatch, 0, len(r.Matched)+len(r.Unmatched))
	files = append(files, r.Matched...)
	files = append(files, r.Unmatched...)
	sort.Slice(files, func(i, j int) bool { return files[i].File.Rel < files[j].File.Rel })

	var out []warnLine
	for _, fm := range files {
		for _, w := range fm.Warnings {
			out = append(out, warnLine{fm.File.Rel, w})
		}
	}
	return out
}

// printWarnings lists one line per warning, Rel padded to the widest shown
// (capped at 40).
func printWarnings(w io.Writer, lines []warnLine) {
	rels := make([]string, len(lines))
	for i, l := range lines {
		rels[i] = l.rel
	}
	width := relWidth(rels)
	for _, l := range lines {
		fmt.Fprintf(w, "  %s  %s\n", padCell(l.rel, width), l.text)
	}
}

// printSkipped lists each skipped file, Rel padded to the widest shown
// (capped at 40), then its reason.
func printSkipped(w io.Writer, skipped []scan.Skipped) {
	rels := make([]string, len(skipped))
	for i, s := range skipped {
		rels[i] = s.Rel
	}
	width := relWidth(rels)
	for _, s := range skipped {
		fmt.Fprintf(w, "  %s  %s\n", padCell(s.Rel, width), s.Reason.String())
	}
}

// skipReasonOrder is the order the last line reports skip reasons in,
// after "not matched".
var skipReasonOrder = []scan.Reason{scan.Ignored, scan.Busy, scan.TooNew, scan.Symlink, scan.NotRegular, scan.Unreadable}

// skipSummaryLine builds the "not matched: N · ignored: N ..." line, only
// the non-zero counts, or "" when every count is zero.
func skipSummaryLine(r *engine.Result, verbose bool) string {
	counts := map[scan.Reason]int{}
	for _, s := range r.Skipped {
		counts[s.Reason]++
	}

	var parts []string
	if n := len(r.Unmatched); n > 0 {
		parts = append(parts, fmt.Sprintf("not matched: %d", n))
	}
	for _, reason := range skipReasonOrder {
		if n := counts[reason]; n > 0 {
			parts = append(parts, fmt.Sprintf("%s: %d", reason.String(), n))
		}
	}
	if len(parts) == 0 {
		return ""
	}
	line := strings.Join(parts, " · ")
	if !verbose {
		line += "   (-v lists them)"
	}
	return line
}

// relWidth returns the column width for a list of Rel names: the widest in
// runes (C4: not bytes, or a name carrying diacritics misaligns its
// column), capped at 40.
func relWidth(rels []string) int {
	w := 0
	for _, s := range rels {
		if n := utf8.RuneCountInString(s); n > w {
			w = n
		}
	}
	if w > 40 {
		w = 40
	}
	return w
}

// padCell pads s to width w (runes, not bytes) with trailing spaces; s
// already at or beyond w is left unpadded.
func padCell(s string, w int) string {
	n := utf8.RuneCountInString(s)
	if n >= w {
		return s
	}
	return s + strings.Repeat(" ", w-n)
}