// ingestion/internal/frontmatter/frontmatter_test.go
package frontmatter

import (
	"testing"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
	"gopkg.in/yaml.v3"
)

func TestLint(t *testing.T) {
	tests := []struct {
		name    string
		doc     string
		wantErr bool
	}{
		{
			name: "no frontmatter block is not an error",
			doc:  "# Just a heading\n\nSome body text.\n",
		},
		{
			name: "quoted title parses",
			doc:  "---\ntitle: 'Headless dispatch runs: Bash is denied'\n---\n\nbody\n",
		},
		{
			name: "plain title parses",
			doc:  "---\ntitle: A simple title\nwing: homelab\n---\n\nbody\n",
		},
		{
			name:    "unquoted colon in title does not parse",
			doc:     "---\ntitle: Headless dispatch runs: Bash is denied — use gitea MCP\nwing: homelab\n---\n\nbody\n",
			wantErr: true,
		},
		{
			// Known gap, deliberately not fixed here: this parses, but the
			// item becomes map[string]any{"Headless dispatch": "denied"}
			// rather than a string. It is a silent type corruption, not a
			// parse failure, so repairing it would rewrite documents that
			// currently load — out of scope for a lint about broken YAML.
			name: "unquoted colon in a list item parses as a mapping, not an error",
			doc:  "---\ntitle: Fine\naliases:\n  - Headless dispatch: denied\n---\n\nbody\n",
		},
		{
			name: "unterminated frontmatter is not treated as frontmatter",
			doc:  "---\ntitle: no closing fence\n\nbody\n",
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			err := Lint([]byte(tt.doc))
			if tt.wantErr {
				require.Error(t, err)
				return
			}
			require.NoError(t, err)
		})
	}
}

func TestFix(t *testing.T) {
	tests := []struct {
		name        string
		doc         string
		wantChanged bool
		wantKey     string
		wantValue   string
	}{
		{
			name:        "quotes an unquoted title containing a colon",
			doc:         "---\ntitle: Headless dispatch runs: Bash is denied — use gitea MCP\nwing: homelab\n---\n\nbody\n",
			wantChanged: true,
			wantKey:     "title",
			wantValue:   "Headless dispatch runs: Bash is denied — use gitea MCP",
		},
		{
			// Parses already (see the Lint table), so Fix must leave it alone
			// rather than rewrite a document that loads.
			name:        "leaves a colon-bearing list item alone because it already parses",
			doc:         "---\ntitle: Fine\naliases:\n  - Headless dispatch: denied\n---\n\nbody\n",
			wantChanged: false,
			wantKey:     "title",
			wantValue:   "Fine",
		},
		{
			name:        "escapes an embedded single quote when quoting",
			doc:         "---\ntitle: Don't do this: it breaks\n---\n\nbody\n",
			wantChanged: true,
			wantKey:     "title",
			wantValue:   "Don't do this: it breaks",
		},
		{
			// The value opens with a double quote and then keeps going after
			// the closing one, so YAML reads it as a quoted scalar followed by
			// junk. Treating "starts with a quote" as "already quoted" leaves
			// this broken forever.
			name:        "quotes a value that only looks quoted",
			doc:         "---\ntitle: \"Evaluation Driven Generation\" — a TDD-style scaffold\ntags: [a, b]\n---\n\nbody\n",
			wantChanged: true,
			wantKey:     "title",
			wantValue:   "\"Evaluation Driven Generation\" — a TDD-style scaffold",
		},
		{
			name:        "leaves an already-valid document untouched",
			doc:         "---\ntitle: 'Already quoted: fine'\nwing: homelab\n---\n\nbody\n",
			wantChanged: false,
			wantKey:     "title",
			wantValue:   "Already quoted: fine",
		},
		{
			name:        "leaves a document with no frontmatter untouched",
			doc:         "# Heading\n\nbody: with a colon\n",
			wantChanged: false,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			got, changed, err := Fix([]byte(tt.doc))
			require.NoError(t, err)
			assert.Equal(t, tt.wantChanged, changed)

			if !tt.wantChanged {
				assert.Equal(t, tt.doc, string(got), "unchanged docs must be returned byte-identical")
			}

			// Whatever came back must parse — that is the whole point.
			require.NoError(t, Lint(got), "Fix must not return a document that still fails to parse")

			if tt.wantKey == "" {
				return
			}
			block, ok := block(got)
			require.True(t, ok)
			var m map[string]any
			require.NoError(t, yaml.Unmarshal(block, &m))
			assert.Equal(t, tt.wantValue, m[tt.wantKey], "the value must survive quoting unchanged")
		})
	}
}

func TestFix_LeavesStructuredValuesStructured(t *testing.T) {
	// Only the broken scalar may be touched. A flow sequence on a neighbouring
	// line still has to load as a sequence afterwards, not as a string.
	doc := "---\ntitle: Broken: here\ntags: [prompting, llm]\ncount: 3\n---\n\nbody\n"

	got, changed, err := Fix([]byte(doc))
	require.NoError(t, err)
	require.True(t, changed)

	b, ok := block(got)
	require.True(t, ok)
	var m map[string]any
	require.NoError(t, yaml.Unmarshal(b, &m))

	assert.Equal(t, "Broken: here", m["title"])
	assert.Equal(t, []any{"prompting", "llm"}, m["tags"])
	assert.Equal(t, 3, m["count"])
}

func TestFix_PreservesBodyExactly(t *testing.T) {
	body := "\nThe body has: colons, 'quotes', and\n---\na horizontal rule.\n"
	doc := "---\ntitle: Broken: title\n---" + body

	got, changed, err := Fix([]byte(doc))
	require.NoError(t, err)
	require.True(t, changed)
	assert.True(t, len(got) > 0)

	_, rest, ok := Split([]byte(doc))
	require.True(t, ok)
	_, gotRest, ok := Split(got)
	require.True(t, ok)
	assert.Equal(t, string(rest), string(gotRest), "the body must not be touched")
}

func TestFix_RefusesToReturnAnUnparseableResult(t *testing.T) {
	// A frontmatter block that quoting cannot rescue: the structure itself is
	// broken, not a scalar. Fix must return the original and an error rather
	// than a half-repaired document.
	doc := "---\ntitle: fine\n\tbad: tab-indented mapping\n  - stray list item\n---\n\nbody\n"

	got, changed, err := Fix([]byte(doc))
	require.Error(t, err)
	assert.False(t, changed)
	assert.Equal(t, doc, string(got), "an unfixable document must come back byte-identical")
}

// TestSplit_NormalizesCRLFBeforeFenceDetection is hyperguild#138: a note
// whose fence lines use CRLF ("---\r\n") failed strings.HasPrefix(doc,
// "---\n") on the precondition read in internal/mcp's independent
// reimplementation -- encoding alone, no adversarial input, silently
// defeated fence detection there before this consolidation. Split must
// never repeat that.
func TestSplit_NormalizesCRLFBeforeFenceDetection(t *testing.T) {
	doc := "---\r\ntitle: 'n'\r\nhalf_life: durable\r\n---\r\n\r\nbody\r\n"
	block, rest, ok := Split([]byte(doc))
	require.True(t, ok)
	assert.Contains(t, string(block), "half_life: durable")
	assert.Contains(t, string(rest), "body")
}

// TestSplit_StripsALeadingUTF8BOM is the same mechanism one layer earlier:
// a leading BOM (Notepad's default "UTF-8" save, PowerShell's pre-v6
// Out-File/Set-Content) defeats the same HasPrefix check before CRLF
// normalization even applies.
func TestSplit_StripsALeadingUTF8BOM(t *testing.T) {
	doc := "\xef\xbb\xbf---\ntitle: 'n'\n---\n\nbody\n"
	block, rest, ok := Split([]byte(doc))
	require.True(t, ok)
	assert.Contains(t, string(block), "title: 'n'")
	assert.Contains(t, string(rest), "body")
}

// TestSplit_RequiresANewlineAfterTheClosingFence closes the looser match
// internal/api's independent reimplementation carried (strings.Index(body,
// "\n"+fence) with no trailing-newline requirement): a document ending in
// "\n---extra" with no newline separating the fence from what follows it is
// not a valid closing fence and must not be treated as one.
func TestSplit_RequiresANewlineAfterTheClosingFence(t *testing.T) {
	doc := "---\ntitle: 'n'\n---extra-not-a-real-close"
	_, _, ok := Split([]byte(doc))
	assert.False(t, ok, "a fence line not followed by a newline is not a valid closing fence")
}