#!/usr/bin/env nu
# Check for malformed closing code fences in markdown files
# Malformed: ```plaintext (closing fence with language specifier)
# Correct: ``` (just three backticks)
#
# Markdownlint does NOT catch this natively (MD040 only checks opening fences)
# This is a CommonMark violation that must be checked separately
#
# Usage:
#   nu check-malformed-fences.nu              # Check all markdown files
#   nu check-malformed-fences.nu file.md      # Check specific file
#   nu check-malformed-fences.nu **/*.md      # Check pattern

def main [
    ...files: string  # Files to check (or empty for all)
] {
    let md_files = if ($files | is-empty) {
        glob **/*.md
        | where { |f| $f !~ "node_modules" }
        | where { |f| $f !~ "target" }
        | where { |f| $f !~ ".git" }
        | where { |f| $f !~ "build" }
        | where { |f| $f !~ "dist" }
        | where { |f| $f !~ ".coder" }
        | where { |f| $f !~ ".claude" }
        | where { |f| $f !~ "old_config" }
    } else {
        $files
    }

    mut errors = []
    mut checked_count = 0

    for file in $md_files {
        $checked_count = $checked_count + 1

        let content = open $file | lines
        mut in_fence = false
        mut fence_lang = ""
        mut fence_start = 0

        for line in ($content | enumerate) {
            let idx = $line.index
            let text = $line.item

            # Check if this is a code fence line
            if ($text =~ '^```') {
                if not $in_fence {
                    # Opening fence
                    if ($text =~ '^```\w+') {
                        $in_fence = true
                        $fence_lang = ($text | str substring 3..)
                        $fence_start = $idx + 1
                    }
                } else {
                    # We're inside a fence, so this must be a closing fence
                    if ($text =~ '^```\w+\s*$') {
                        # MALFORMED: closing fence has language
                        $errors = ($errors | append {
                            file: $file,
                            line: ($idx + 1),
                            fence_opened: $fence_start,
                            opening_lang: $fence_lang,
                            closing_text: $text,
                        })
                    }
                    # Reset fence state regardless
                    $in_fence = false
                }
            }
        }
    }

    print $"🔍 Checked ($checked_count) markdown files"
    print ""

    if ($errors | is-empty) {
        print "✅ No malformed closing fences found"
        print ""
        print "All closing fences are correct: ``` (no language specifier)"
        exit 0
    } else {
        print $"❌ Found ($errors | length) malformed closing fences"
        print ""
        print "Closing fences must NOT have language specifiers (CommonMark violation)"
        print ""

        for e in $errors {
            print $"  ($e.file):($e.line)"
            print $"    Opened at line ($e.fence_opened) with: ```($e.opening_lang)"
            print $"    ❌ WRONG: ($e.closing_text | str trim)"
            print $"    ✅ FIX TO: ```"
            print ""
        }

        print "How to fix:"
        print "  Replace closing fences like ```plaintext with just ```"
        print ""
        exit 1
    }
}