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

package main

import (
	"fmt"
	"io"
	"path/filepath"
	"strconv"
	"strings"
	"unicode/utf8"

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

// actionKindWidth is the field an action cell's kind word is left-padded
// to before its arrow: the widest of the three kinds that carry a
// destination ("copy", "move", "rename"). Trash and DELETE permanently
// have no destination, hence no arrow to align, so they are not padded.
const actionKindWidth = len("rename")

// printPlan renders one directory's plan the way krino -n shows it, per
// spec §8.2, below the header line cmdSort has already written: a counts
// line, the numbered action table, the warnings section and the "not
// acted on" line, each present only when it has something to show. No
// colour, pager or prompt: those arrive with the review UI in plan 4,
// which wraps this same function, hence its plain (io.Writer, *DirPlan,
// bool) signature.
func printPlan(w io.Writer, dp *engine.DirPlan, verbose bool) {
	r := dp.Result
	// C1 (plan 2): scanned counts matched, unmatched and skipped alike, not
	// just matched plus unmatched - 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.
	scanned := len(r.Matched) + len(r.Unmatched) + len(r.Skipped)
	// B2: warning lines come from both the match itself (fm.Warnings) and
	// the chains plan.Build produced (Chain.Warnings, e.g. "moved more than
	// once") - both computed once here so the count and the section below
	// agree on the exact same list.
	lines := collectWarnings(r, dp.Chains)
	// D12: dp.Elapsed spans Match plus Build, unlike r.Elapsed, which stops
	// before Build ever runs - the label says "planning", so the number
	// must cover all of it.
	fmt.Fprintf(w, "%d scanned · %d to act on · %d warnings · %.2fs\n", scanned, countActing(dp.Chains), warnedCount(lines), dp.Elapsed.Seconds())

	if rows := planRows(dp.Chains, dp.Dir.Root); len(rows) > 0 {
		fmt.Fprintln(w)
		printPlanTable(w, rows)
	}

	if len(lines) > 0 {
		fmt.Fprintln(w)
		fmt.Fprintln(w, "warnings")
		printWarnings(w, lines)
	}

	if line := skipSummaryLine(r, dp.Chains, 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)
		}
	}
}

// chainActing reports whether c has at least one step that will actually
// run - the single definition of "actionable" that countActing,
// actionableChains (sort.go) and chainOutcomes (sort.go) all share (fix
// wave item 4 / Minor 5). Before this fix, countActing and actionableChains
// each kept their own copy of this question and disagreed: countActing
// excluded an all-skipped chain (len(Steps) > 0, but every step's Skip is
// set) while actionableChains's own len(Steps) > 0 check included it, so a
// directory could print "N scanned · 0 to act on" and then still ask the
// user to approve a file it had just said there were none of - and on
// approval, log a run-start/run-end pair holding only "skipped" entries.
func chainActing(c plan.Chain) bool {
	for _, s := range c.Steps {
		if s.Skip == "" {
			return true
		}
	}
	return false
}

// countActing reports how many chains have at least one step that will
// actually run. C1/ruling 2026-09-12: a rule with no actions is an
// exclusion, and a chain every one of whose steps is skipped is not about
// to do anything either - neither must inflate "to act on".
func countActing(chains []plan.Chain) int {
	n := 0
	for _, c := range chains {
		if chainActing(c) {
			n++
		}
	}
	return n
}

// planRow is one line of the action table: a file's first step (num and
// file set) or a continuation line (both blank). chainIdx (D15) is the
// index into the DirPlan's own Chains slice this row was built from, kept
// alongside the display strings so plan 4's per-file approval ("row 2 is
// chain index 1", spec §8.3) does not have to re-derive the mapping later;
// it changes no rendering here and is not itself asserted by a test.
type planRow struct {
	num, file, actions, rule, reason string
	chainIdx                         int
}

// planRows turns the chains that have at least one step into table rows,
// per spec §8.2: a file's first step shares its numbered row; later steps
// sit on continuation lines with the number and file columns blank. A
// chain with no steps at all - an exclusion, or a rule that only stops -
// has nothing to show and contributes no row and no number. root is the
// directory being planned, threaded down to destText so a destination
// inside it renders root-relative rather than home-abbreviated.
func planRows(chains []plan.Chain, root string) []planRow {
	var rows []planRow
	n := 0
	for ci, c := range chains {
		if len(c.Steps) == 0 {
			continue
		}
		n++
		for i, s := range c.Steps {
			row := planRow{actions: actionCell(s, root), rule: s.Rule, reason: s.Reason, chainIdx: ci}
			if i == 0 {
				row.num = strconv.Itoa(n)
				row.file = c.File.Rel
			}
			rows = append(rows, row)
		}
	}
	return rows
}

// actionCell renders one step's action column. A step with Skip set shows
// its reason in place of the destination. Trash and DELETE permanently
// have no destination to show - even when the step came from a duplicate
// rule, the reason column already says what it is a duplicate of, so the
// action column is just the kind word. Everything else (copy, move,
// rename) shows the kind, padded so every arrow in the table lines up,
// then its destination; Displaces adds a trailing note.
func actionCell(s plan.Step, root string) string {
	kind := s.Kind.String()
	if s.Skip != "" {
		return padCell(kind, actionKindWidth) + "  skipped: " + s.Skip
	}
	switch s.Kind {
	case plan.Trash, plan.DeletePermanent:
		return kind
	}
	cell := padCell(kind, actionKindWidth) + "  → " + destText(s, root)
	if s.Displaces != "" {
		cell += " (replaces the existing file)"
	}
	return cell
}

// destText renders a copy/move/rename step's destination, per spec §8.2:
// for rename, just the new base name. For copy and move, a directory with
// a trailing "/" so it reads as one - root-relative when it lies inside
// the directory being planned (spec's own worked example: "Work/Acme/"),
// abbreviated against $HOME otherwise (the same example's
// "~/backup/invoices/2026/", outside the root entirely).
func destText(s plan.Step, root string) string {
	if s.Kind == plan.Rename {
		return filepath.Base(s.Dst)
	}
	dir := filepath.Dir(s.Dst)
	if rel, ok := relToRoot(root, dir); ok {
		if rel == "" {
			// D10: rel is "" exactly when dir is root itself (relToRoot's
			// own case below); rendering that as bare rel+"/" would print
			// "/", which reads as the filesystem root rather than "this
			// directory".
			return "./"
		}
		return rel + "/"
	}
	return xdg.Abbrev(dir) + "/"
}

// relToRoot returns dir relative to root (slash-separated) when dir is
// root itself or lies inside it; ok is false when dir lies outside root,
// including when the two cannot be related at all (e.g. one relative, one
// absolute). C3: root itself counts as "inside" here (rel is "", ok true) -
// unlike internal/engine/match.go's excludeDirs, which asks a different
// question (what may a rule exclude from the walk) and treats root as
// outside it; do not "unify" the two.
func relToRoot(root, dir string) (rel string, ok bool) {
	r, err := filepath.Rel(root, dir)
	if err != nil || r == ".." || strings.HasPrefix(r, ".."+string(filepath.Separator)) {
		return "", false
	}
	if r == "." {
		return "", true // dir is root itself
	}
	return filepath.ToSlash(r), true
}

// printPlanTable prints rows in the table layout of spec §8.2: #, file,
// actions and rule are padded to what is actually shown in this section,
// in runes, exactly as relWidth/padCell already do elsewhere; the file
// column is capped at 40 and the actions column at 46. The reason is the
// last column and is never padded. The row number is right-aligned
// (padLeft, not padCell) so the "#" column stays flush as it widens past
// a single digit - the layout plan 4's review UI inherits unchanged.
func printPlanTable(w io.Writer, rows []planRow) {
	nums := make([]string, len(rows))
	files := make([]string, len(rows))
	actions := make([]string, len(rows))
	rules := make([]string, len(rows))
	for i, r := range rows {
		nums[i], files[i], actions[i], rules[i] = r.num, r.file, r.actions, r.rule
	}
	// D13: numW and ruleW are left uncapped, unlike fileW and actionsW. The
	// row number is at most a few digits regardless of how large a
	// directory is, and a rule name is a config author's own identifier,
	// not scan noise from a user's file names - truncating a name someone
	// deliberately chose would only make the row harder to trace back to
	// its rule, so there is nothing here worth capping.
	numW := colWidth(nums, 0)
	fileW := relWidth(files)
	actionsW := colWidth(actions, 46)
	ruleW := colWidth(rules, 0)

	fmt.Fprintf(w, "  %s  %s  %s  rule\n", padLeft("#", numW), padCell("file", fileW), padCell("actions", actionsW))
	for _, r := range rows {
		fmt.Fprintf(w, "  %s  %s  %s  %s  %s\n", padLeft(r.num, numW), padCell(r.file, fileW), padCell(r.actions, actionsW), padCell(r.rule, ruleW), r.reason)
	}
}

// padLeft pads s to width w (runes, not bytes) with leading spaces,
// right-aligning it; s already at or beyond w is left unpadded. Used only
// for the row-number column - every other column reads left-aligned, per
// padCell.
func padLeft(s string, w int) string {
	n := utf8.RuneCountInString(s)
	if n >= w {
		return s
	}
	return strings.Repeat(" ", w-n) + s
}

// colWidth returns the widest string in ss, in runes, capped at max when
// max is positive; 0 leaves it uncapped. Shares relWidth's rune-counting
// rule (C4): a name carrying diacritics must not misalign its column.
func colWidth(ss []string, max int) int {
	w := 0
	for _, s := range ss {
		if n := utf8.RuneCountInString(s); n > w {
			w = n
		}
	}
	if max > 0 && w > max {
		w = max
	}
	return w
}