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

package main

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

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

// cmdSort plans and applies the included directories. Only -n (dry run) is
// implemented; applying arrives in plan 4.
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 && !g.dry {
		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
	jsonDirs := []plan.JSONDir{} // never nil: the document's "dirs" must marshal as [], not null
	// A3: one Claims for the whole run, shared across every directory's
	// Plan call below, so two directories that both plan a move to the
	// same destination resolve the collision at planning time instead of
	// each independently believing it owns that path.
	claims := plan.NewClaims()
	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
		}
		dp, err := e.Plan(context.Background(), d, claims)
		if err != nil {
			fmt.Fprintf(stderr, "krino: skipping %s: %v\n", d.Name, err)
			exit = 1
			continue
		}
		if !g.json {
			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 dp.Result.Warnings {
			fmt.Fprintf(stderr, "krino: %s: %s\n", d.Name, w)
		}
		if g.json {
			jsonDirs = append(jsonDirs, plan.NewJSONDir(d.Name, d.Root, dp.Chains, dp.Result.Warnings))
			continue
		}
		printPlan(stdout, dp, g.verbose)
	}

	if g.json {
		b, err := json.MarshalIndent(plan.NewJSON(jsonDirs), "", "  ")
		if err != nil {
			// Unreachable in practice: every field the document carries
			// marshals cleanly (strings, times, ints).
			fmt.Fprintf(stderr, "krino: %v\n", err)
			return 1
		}
		stdout.Write(b)
		fmt.Fprintln(stdout)
	}
	return exit
}

// 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: its match warnings (if any)
// first, then its chain warnings (B2) - match happens before planning, so
// that is also the order they were actually produced in. chains supplies
// the chain-level warnings (e.g. "moved more than once"), keyed by
// Chain.File.Rel; every chain's file is necessarily also in r.Matched (only
// matched files ever reach plan.Build), so it is visited exactly once here.
func collectWarnings(r *engine.Result, chains []plan.Chain) []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 })

	chainWarnings := make(map[string][]string, len(chains))
	for _, c := range chains {
		if len(c.Warnings) > 0 {
			chainWarnings[c.File.Rel] = c.Warnings
		}
	}

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

// warnedCount counts the distinct files behind lines: B2's "N warnings" in
// the counts line must count a file once even when it carries both a match
// warning and a chain warning, not once per warning line.
func warnedCount(lines []warnLine) int {
	seen := make(map[string]bool, len(lines))
	for _, l := range lines {
		seen[l.rel] = true
	}
	return len(seen)
}

// 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 plan 2's reviewed order for the skip reasons the last
// line reports, before "unmatched".
var skipReasonOrder = []scan.Reason{scan.Ignored, scan.Busy, scan.TooNew, scan.Symlink, scan.NotRegular, scan.Unreadable}

// skipSummaryLine builds the "not acted on: N ignored · N busy · ... · N
// unmatched" line per spec §8.2's item format ("<count> <label>", not
// "<label>: <count>"), only the non-zero counts, or "" when every count is
// zero. Ordering is plan 2's reviewed skipReasonOrder, with "unmatched"
// last: the spec's own worked example shows only three of the seven
// categories and states no ordering rule, so its incidental order is not
// adopted, only its item format and unmatched's trailing position.
func skipSummaryLine(r *engine.Result, chains []plan.Chain, verbose bool) string {
	counts := map[scan.Reason]int{}
	for _, s := range r.Skipped {
		counts[s.Reason]++
	}

	var parts []string
	for _, reason := range skipReasonOrder {
		if n := counts[reason]; n > 0 {
			parts = append(parts, fmt.Sprintf("%d %s", n, reason.String()))
		}
	}
	// excluded and allSkipped (chainOutcomes) close the same arithmetic gap:
	// without them, a file matching only an action-less rule, or one whose
	// every step was skipped, is neither "to act on", unmatched, nor a walk
	// skip, so it appears nowhere.
	excluded, allSkipped := chainOutcomes(chains)
	if excluded > 0 {
		parts = append(parts, fmt.Sprintf("%d excluded", excluded))
	}
	if allSkipped > 0 {
		parts = append(parts, fmt.Sprintf("%d all steps skipped", allSkipped))
	}
	if n := len(r.Unmatched); n > 0 {
		parts = append(parts, fmt.Sprintf("%d unmatched", n))
	}
	if len(parts) == 0 {
		return ""
	}
	line := "not acted on: " + strings.Join(parts, " · ")
	if !verbose {
		line += "   (-v lists them)"
	}
	return line
}

// chainOutcomes counts two of skipSummaryLine's categories over chains:
// excluded is chains with no steps at all (a file that matched only rules
// carrying no actions - spec §4.5: "a rule with only (stop) is an
// exclusion"); allSkipped is chains with at least one step, none of them
// unskipped (every step's Skip is set). Neither is "to act on", neither is
// unmatched, and neither is a walk skip, so without these two counts they
// appear nowhere: the real downloads folder reported "267 scanned · 172 to
// act on" and said nothing at all about the other 95. With them the
// arithmetic always closes - scanned = to act on + excluded + all steps
// skipped + unmatched + walk skips - as spec §8.2's own example does.
func chainOutcomes(chains []plan.Chain) (excluded, allSkipped int) {
	for _, c := range chains {
		if len(c.Steps) == 0 {
			excluded++
			continue
		}
		acting := false
		for _, s := range c.Steps {
			if s.Skip == "" {
				acting = true
				break
			}
		}
		if !acting {
			allSkipped++
		}
	}
	return excluded, allSkipped
}

// 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)
}