package linthost

import "testing"

// TestDisplayWidthMatchesPrettierGetStringWidth verifies displayWidth returns
// the number Prettier 3.8.3 returns for each listed string.
//
// These frozen expectations were recorded as Prettier 3.8.3 measurements,
// except the documented tab deviation. The unit compares displayWidth with
// those literals; it does not call Prettier or verify installed-version
// agreement. The literals are not generated from the implementation under test.
//
// Inputs are written as `\u` escapes on purpose. Several are unassigned, several
// are invisible, and one is a lone keycap mark; verify the code points, not the
// glyphs, before changing any of them. `＀`, `⺚`, and `꓇` measure
// 1 precisely BECAUSE they are unassigned, so replacing one with its assigned
// neighbour inverts the assertion silently.
//
// @evidence contracts/testing.md#behavioral-verification displayWidth must reproduce the frozen Prettier width corpus, including complete versus incomplete emoji sequences, combining code points and the documented one-column tab deviation.
// @evidence contracts/testing.md#independent-expectations The independently supplied frozen literals are recorded as Prettier 3.8.3 measurements, with a documented tab deviation; this unit neither regenerates expectations from displayWidth nor remeasures Prettier. Range shape checks are prerequisites, not proof of installed-version agreement.
// @evidence contracts/testing.md#distinguishing-cases The named matrix retains empty/control, assigned/unassigned, text versus emoji, combining marks, lone selectors, ASCII fast-path DEL and mixed lines. Each t.Run case keeps its name and assertion.
// @evidence contracts/testing.md#execution-ownership TestDisplayWidthMatchesPrettierGetStringWidth is a top-level Go unit selected by the Go tests Evidence claim. It calls its private range-table precondition helper, then displayWidth in each named t.Run case in-process; it installs no consumer, builds no native artifact and starts no formatter child or product host.
func TestDisplayWidthMatchesPrettierGetStringWidth(t *testing.T) {
  assertDisplayWidthOraclePreconditions(t)
  for _, tc := range []struct {
    name  string
    input string
    want  int
  }{
    // Emoji the old range table under-charged.
    {"star", "⭐", 2},
    {"check-mark", "✅", 2},
    {"cross-mark", "❌", 2},
    {"high-voltage", "⚡", 2},
    {"watch", "⌚", 2},
    {"mahjong-red-dragon", "\U0001F004", 2},
    {"hexagram", "䷀", 2},
    {"small-comma", "﹐", 2},

    // Emoji sequences: the regex substitution charges each whole.
    {"heart-with-vs16", "❤\uFE0F", 2},
    {"keycap-one", "1\uFE0F\u20E3", 2},
    {"waving-hand-skin-tone", "\U0001F44B\U0001F3FD", 2},
    {"zwj-family", "\U0001F468\u200D\U0001F469\u200D\U0001F467", 2},
    // Not every ZWJ chain is an RGI sequence. This one is not, so the regex
    // does not match it whole and its parts are charged: 2 + 1 + 2.
    {"incomplete-zwj-sequence", "\U0001F468\u200D\U0001F469", 5},
    {"regional-indicator-flag", "\U0001F1F0\U0001F1F7", 2},

    // Emoji-regex matches these bare although they default to text
    // presentation, so they are two columns while Emoji_Presentation is false.
    // A `string-width` port charges them 1.
    {"thermometer-text-presentation", "\U0001F321", 2},
    {"eye-text-presentation", "\U0001F441", 2},
    {"detective-text-presentation", "\U0001F575", 2},
    // A skin tone on a base that is itself narrow.
    {"index-pointing-up-skin-tone", "☝\U0001F3FD", 2},

    // Ranges the old table over-charged.
    {"ornamental-leaf", "\U0001F650", 1},
    {"circled-number-ten", "㉈", 1},
    {"unassigned-cjk-radical", "⺚", 1},
    {"unassigned-yi-radical", "꓇", 1},
    {"unassigned-fullwidth", "＀", 1},
    // Half of a flag is not a flag; the regex needs the pair.
    {"lone-regional-indicator", "\U0001F1F0", 1},
    // A copyright sign is an emoji Prettier charges one column.
    {"narrow-emoji-copyright", "©", 1},

    // Counted per CODE POINT, not per grapheme cluster. Charging a cluster's
    // base alone is what made a `string-width` port wrong on ordinary text.
    {"devanagari-ka-aa", "का", 2},
    {"hindi-word", "हिंदी", 5},
    {"decomposed-hangul", "한", 4},
    {"base-with-combining-mark", "가\u0301", 2},

    // Not skipped: only U+0300-U+036F, the C0/C1 controls, and U+FE00-U+FE0F
    // are free. A default-ignorable skip would zero all of these.
    {"hangul-filler", "\u115F", 2},
    {"halfwidth-hangul-filler", "\u3164", 2},
    {"zero-width-non-joiner", "\u200C", 1},
    {"left-to-right-mark", "\u200E", 1},
    {"soft-hyphen", "\u00AD", 1},
    {"zero-width-space", "\u200B", 1},
    {"byte-order-mark", "\uFEFF", 1},
    {"lone-zwj", "\u200D", 1},
    {"lone-keycap-mark", "\u20E3", 1},
    // A variation selector on a base the emoji regex does not match is free,
    // and its base is charged normally.
    {"a-with-vs16", "a\uFE0F", 1},
    {"hash-with-vs16", "#\uFE0F", 1},
    {"lone-variation-selector", "\uFE0F", 0},
    {"lone-combining-mark", "\u0301", 0},

    // Already correct, and must stay correct.
    {"ascii", "a", 1},
    {"ascii-run", "const value = 1;", 16},
    {"hangul-syllable", "가", 2},
    {"cjk-unified", "一", 2},
    {"subscript-digit", "₀", 1},
    {"empty", "", 0},
    {"control-character", "\x07", 0},
    {"carriage-return-and-newline", "a\r\nb", 2},
    // U+007F rides the printable-ASCII fast path, which the counting loop
    // would have skipped. The fast path is observable, not an optimization.
    {"delete-through-the-ascii-fast-path", "\x7F", 1},

    // The one deliberate deviation: Prettier's loop skips a tab as a control
    // and returns 0. The layout engine emits indentation outside the text it
    // measures, so a tab is charged one column here and tab-stop expansion is
    // `displayWidthFromColumn`'s.
    {"tab-keeps-its-documented-one-column", "\t", 1},

    // A mixed line, the shape the formatter actually measures: five stars cost
    // the same ten columns as ten ASCII characters.
    {"mixed-line", "fn(\"⭐⭐⭐⭐⭐\", 1);", 20},
  } {
    t.Run(tc.name, func(t *testing.T) {
      if got := displayWidth(tc.input); got != tc.want {
        t.Fatalf("displayWidth(%q) = %d, want %d", tc.input, got, tc.want)
      }
    })
  }
}