// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
// SPDX-License-Identifier: BSD-3-Clause

package main

import (
	"os"
	"os/exec"
	"path/filepath"
	"regexp"
	"strings"
	"testing"
)

// TestManPagesTrackTheCLI builds the binary once, then compares every
// command's live `-h` output with its docs/man/gasm-<command>.1 page: the
// flag sets must agree both ways, and the page's SYNOPSIS line must carry
// the command's usage line.  A flag or a usage change that skips the man
// page fails here, so the pages cannot drift from the binary.
func TestManPagesTrackTheCLI(t *testing.T) {
	if testing.Short() {
		t.Skip("builds the gasm binary")
	}
	bin := filepath.Join(t.TempDir(), "gasm")
	if out, err := exec.Command("go", "build", "-o", bin, ".").CombinedOutput(); err != nil {
		t.Fatalf("build gasm: %v\n%s", err, out)
	}

	for _, cmd := range []string{
		"tokens", "parse", "fmt", "lint", "asm", "dis", "verify",
		"debug", "diff", "profile", "audit-instructions", "scaffold", "lsp",
	} {
		t.Run(cmd, func(t *testing.T) {
			raw, err := os.ReadFile(filepath.Join("..", "..", "docs", "man", "gasm-"+cmd+".1"))
			if err != nil {
				t.Fatalf("read man page: %v", err)
			}
			page := string(raw)

			out, _ := exec.Command(bin, cmd, "-h").CombinedOutput()
			help := string(out)

			binFlags := helpFlags(help)
			pageFlags := roffFlags(page)
			for f := range binFlags {
				if !pageFlags[f] {
					t.Errorf("flag -%s is in the binary's help but missing from the man page", f)
				}
			}
			for f := range pageFlags {
				if !binFlags[f] {
					t.Errorf("flag -%s is in the man page but the binary does not accept it", f)
				}
			}

			want := helpUsage(help)
			got := roffSynopsis(page)
			if want != "" && got != want {
				t.Errorf("SYNOPSIS drift:\n page: %s\nbinary: %s", got, want)
			}
		})
	}
}

// helpFlags extracts the flag names from a `gasm <cmd> -h` output.
func helpFlags(help string) map[string]bool {
	m := map[string]bool{}
	inFlags := false
	for line := range strings.SplitSeq(help, "\n") {
		if strings.TrimRight(line, " \t") == "Flags:" {
			inFlags = true
			continue
		}
		if !inFlags {
			continue
		}
		if !strings.HasPrefix(line, "  -") {
			continue
		}
		token := strings.FieldsFunc(strings.TrimLeft(line, " "), func(r rune) bool {
			return r == ' ' || r == '\t'
		})
		if len(token) == 0 {
			continue
		}
		m[strings.TrimLeft(token[0], "-")] = true
	}
	return m
}

var roffEscape = regexp.MustCompile(`\\f[BIRP]`)

// roffFlags extracts the flag names from a man page's OPTIONS section.
func roffFlags(page string) map[string]bool {
	m := map[string]bool{}
	inOptions := false
	for line := range strings.SplitSeq(page, "\n") {
		if strings.HasPrefix(line, ".SH ") {
			inOptions = strings.HasPrefix(line, ".SH OPTIONS")
			continue
		}
		if !inOptions {
			continue
		}
		// Flag entries are written as either `.B \-flag` or `\fB\-flag`.
		var body string
		switch {
		case strings.HasPrefix(line, `.B \-`):
			body = line[3:]
		case strings.HasPrefix(line, `\fB\-`):
			body = line[1:]
		default:
			continue
		}
		name := roffEscape.ReplaceAllString(body, "")
		name = strings.ReplaceAll(name, `\-`, "-")
		name = strings.TrimSpace(name)
		if i := strings.IndexAny(name, " \t"); i >= 0 {
			name = name[:i]
		}
		m[strings.TrimLeft(name, "-")] = true
	}
	return m
}

// helpUsage returns the command's usage line without the "Usage: " prefix.
func helpUsage(help string) string {
	for line := range strings.SplitSeq(help, "\n") {
		if strings.HasPrefix(line, "Usage: ") {
			return normaliseUsage(line[len("Usage: "):])
		}
	}
	return ""
}

// roffSynopsis returns the page's SYNOPSIS usage line, unescaped.
func roffSynopsis(page string) string {
	inSyn := false
	for line := range strings.SplitSeq(page, "\n") {
		if strings.HasPrefix(line, ".SH ") {
			inSyn = strings.HasPrefix(line, ".SH SYNOPSIS")
			continue
		}
		if !inSyn || !strings.HasPrefix(line, ".B ") {
			continue
		}
		return normaliseUsage(strings.ReplaceAll(line[3:], `\-`, "-"))
	}
	return ""
}

// normaliseUsage flattens whitespace and drops the roff font escapes so that
// the binary's usage line and the page's SYNOPSIS line compare equal.
func normaliseUsage(s string) string {
	s = roffEscape.ReplaceAllString(s, "")
	return strings.Join(strings.Fields(s), " ")
}