package filter_test

import (
	"fmt"
	"regexp"
	"strings"
	"testing"

	"errors"

	"github.com/gruntwork-io/terragrunt/internal/filter"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

// TestHints_Golden tests the full rendered error messages for golden/regression testing.
func TestHints_Golden(t *testing.T) {
	t.Parallel()

	testCases := []struct {
		name     string
		query    string
		expected string
	}{
		{
			name:  "git syntax caret after ref",
			query: "HEAD^",
			expected: `Filter parsing error: Unexpected token
 --> --filter 'HEAD^'

     HEAD^
         ^ Unexpected '^' after expression

  hint: Git-based expressions require surrounding references with '[]'. Did you mean '[HEAD^]'?
`,
		},
		{
			name:  "unclosed bracket",
			query: "[main...HEAD",
			expected: `Filter parsing error: Unclosed Git filter expression
 --> --filter '[main...HEAD'

     [main...HEAD
     ^ This Git-based expression is missing a closing ']'

  hint: Git-based expressions require surrounding references with '[]'. Did you mean '[main...HEAD]'?
`,
		},
		{
			name:  "unclosed brace",
			query: "{my path",
			expected: `Filter parsing error: Unclosed path expression
 --> --filter '{my path'

     {my path
     ^ This braced path expression is missing a closing '}'

  hint: Explicit path expressions require surrounding paths with '{}'. Did you mean '{my path}'?
`,
		},
		{
			name:  "empty git filter",
			query: "[]",
			expected: `Filter parsing error: Empty Git filter
 --> --filter '[]'

     []
      ^ Git filter expression cannot be empty
`,
		},
		{
			name:  "pipe at start",
			query: "| foo",
			expected: `Filter parsing error: Unexpected token
 --> --filter '| foo'

     | foo
     ^ Missing left-hand side of '|' operator
`,
		},
		{
			name:  "pipe at end",
			query: "foo |",
			expected: `Filter parsing error: Unexpected end of input
 --> --filter 'foo |'

     foo |
          ^ Missing right-hand side of '|' operator
`,
		},
		{
			name:  "bang without operand",
			query: "!",
			expected: `Filter parsing error: Unexpected end of input
 --> --filter '!'

     !
      ^ Missing target expression for '!' operator
`,
		},
		{
			name:  "Unexpected closing bracket",
			query: "]",
			expected: `Filter parsing error: Unexpected token
 --> --filter ']'

     ]
     ^ Unexpected ']'

  hint: Unexpected ']' without matching '['. Git-based expressions use square brackets. e.g. '[main...HEAD]'
`,
		},
		{
			name:  "Unexpected closing brace",
			query: "}",
			expected: `Filter parsing error: Unexpected token
 --> --filter '}'

     }
     ^ Unexpected '}'

  hint: Unexpected '}' without matching '{'. Explicit path expressions use braces. e.g. '{./my path}'
`,
		},
		{
			name:  "equals without context",
			query: "=foo",
			expected: `Filter parsing error: Unexpected token
 --> --filter '=foo'

     =foo
     ^ Unexpected '='

  hint: The equals sign is used for attribute filters. e.g. 'name=foo'
`,
		},
		{
			name:  "caret at start",
			query: "^",
			expected: `Filter parsing error: Unexpected end of input
 --> --filter '^'

     ^
      ^ Expression is incomplete

  hint: The '^' operator must be used in either a graph-based or Git-based expression. e.g. '...^foo...' or '[HEAD^]'
`,
		},
		{
			name:  "ellipsis at start",
			query: "...",
			expected: `Filter parsing error: Unexpected end of input
 --> --filter '...'

     ...
        ^ Expression is incomplete

  hint: The '...' operator must be used in either a graph-based or Git-based expression. e.g. '...foo...' or '[main...HEAD]'
`,
		},
		{
			name:  "missing git ref after ellipsis",
			query: "[main...]",
			expected: `Filter parsing error: Missing Git reference
 --> --filter '[main...]'

     [main...]
             ^ Expected second Git reference after '...'

  hint: Git filters with '...' require a reference on each side. e.g. '[main...HEAD]'
`,
		},
		{
			name:  "complex expression with caret",
			query: "./apps/* | HEAD^",
			expected: `Filter parsing error: Unexpected token
 --> --filter './apps/* | HEAD^'

     ./apps/* | HEAD^
                    ^ Unexpected '^' after expression

  hint: Git-based expressions require surrounding references with '[]'. Did you mean '[HEAD^]'?
`,
		},
		{
			name:  "caret after ellipsis",
			query: "./foo...^",
			expected: `Filter parsing error: Unexpected token
 --> --filter './foo...^'

     ./foo...^
             ^ Unexpected '^' after expression

  hint: The '^' operator excludes the target from graph results when used on the left side of the expression. Did you mean '^./foo...'?
`,
		},
	}

	for _, tc := range testCases {
		t.Run(tc.name, func(t *testing.T) {
			t.Parallel()

			output, err := renderParseError(tc.query)
			require.NoError(t, err)

			output = stripTimestampPrefix(output)

			assert.Equal(t, tc.expected, output)
		})
	}
}

// TestHints_ErrorCodeCoverage verifies that all error codes produce appropriate hints.
func TestHints_ErrorCodeCoverage(t *testing.T) {
	t.Parallel()

	testCases := []struct {
		name          string
		token         string
		query         string
		hintSubstring string
		code          filter.ErrorCode
		position      int
		expectHint    bool
	}{
		{
			name:       "UnexpectedToken with pipe",
			code:       filter.ErrorCodeUnexpectedToken,
			token:      "|",
			query:      "| foo",
			position:   0,
			expectHint: false,
		},
		{
			name:          "UnexpectedToken with caret",
			code:          filter.ErrorCodeUnexpectedToken,
			token:         "^",
			query:         "HEAD^",
			position:      4,
			expectHint:    true,
			hintSubstring: "Git",
		},
		{
			name:          "UnexpectedToken with equals",
			code:          filter.ErrorCodeUnexpectedToken,
			token:         "=",
			query:         "=foo",
			position:      0,
			expectHint:    true,
			hintSubstring: "attribute",
		},
		{
			name:          "UnexpectedToken with closing bracket",
			code:          filter.ErrorCodeUnexpectedToken,
			token:         "]",
			query:         "]",
			position:      0,
			expectHint:    true,
			hintSubstring: "without matching '['",
		},
		{
			name:          "UnexpectedToken with closing brace",
			code:          filter.ErrorCodeUnexpectedToken,
			token:         "}",
			query:         "}",
			position:      0,
			expectHint:    true,
			hintSubstring: "without matching '{'",
		},
		{
			name:          "UnexpectedToken with ellipsis",
			code:          filter.ErrorCodeUnexpectedToken,
			token:         "...",
			query:         "...",
			position:      0,
			expectHint:    true,
			hintSubstring: "graph-based",
		},
		{
			name:          "MissingClosingBracket",
			code:          filter.ErrorCodeMissingClosingBracket,
			token:         "",
			query:         "[main",
			position:      5,
			expectHint:    true,
			hintSubstring: "require surrounding references with '[]'",
		},
		{
			name:          "MissingClosingBrace",
			code:          filter.ErrorCodeMissingClosingBrace,
			token:         "",
			query:         "{path",
			position:      5,
			expectHint:    true,
			hintSubstring: "require surrounding paths with '{}'",
		},
		{
			name:          "MissingGitRef",
			code:          filter.ErrorCodeMissingGitRef,
			token:         "",
			query:         "[main...]",
			position:      8,
			expectHint:    true,
			hintSubstring: "require a reference on each side",
		},
		{
			name:       "MissingOperand",
			code:       filter.ErrorCodeMissingOperand,
			token:      "",
			query:      "foo |",
			position:   5,
			expectHint: false,
		},
		{
			name:          "UnexpectedEOF",
			code:          filter.ErrorCodeUnexpectedEOF,
			token:         "",
			query:         "...",
			position:      3,
			expectHint:    true,
			hintSubstring: "expression",
		},
		{
			name:          "IllegalToken",
			code:          filter.ErrorCodeIllegalToken,
			token:         "@",
			query:         "@",
			position:      0,
			expectHint:    true,
			hintSubstring: "not recognized",
		},
		{
			name:       "EmptyGitFilter - no hint",
			code:       filter.ErrorCodeEmptyGitFilter,
			token:      "]",
			query:      "[]",
			position:   1,
			expectHint: false,
		},
		{
			name:       "EmptyExpression - no hint",
			code:       filter.ErrorCodeEmptyExpression,
			token:      "}",
			query:      "{}",
			position:   1,
			expectHint: false,
		},
		{
			name:       "Unknown - no hint",
			code:       filter.ErrorCodeUnknown,
			token:      "",
			query:      "",
			position:   0,
			expectHint: false,
		},
	}

	for _, tc := range testCases {
		t.Run(tc.name, func(t *testing.T) {
			t.Parallel()

			hint := filter.GetHint(tc.code, tc.token, tc.query, tc.position)

			if tc.expectHint {
				require.NotEmpty(
					t,
					hint,
					"expected hint for error code %v",
					tc.code,
				)
				assert.Contains(
					t,
					hint,
					tc.hintSubstring,
					"hint should contain '%s', got: %s",
					tc.hintSubstring,
					hint,
				)

				return
			}

			assert.Empty(t, hint, "expected no hint for error code %v", tc.code)
		})
	}
}

// TestHints_CaretContextualHints tests that caret hints vary based on context.
func TestHints_CaretContextualHints(t *testing.T) {
	t.Parallel()

	testCases := []struct {
		name          string
		query         string
		hintSubstring string
		position      int
	}{
		{
			name:          "caret after identifier suggests Git syntax",
			query:         "HEAD^",
			position:      4,
			hintSubstring: "[HEAD^]",
		},
		{
			name:          "caret after ellipsis suggests graph exclusion",
			query:         "foo...^bar",
			position:      6,
			hintSubstring: "excludes the target",
		},
		{
			name:          "caret at start suggests graph exclusion",
			query:         "^foo",
			position:      0,
			hintSubstring: "excludes the target",
		},
	}

	for _, tc := range testCases {
		t.Run(tc.name, func(t *testing.T) {
			t.Parallel()

			hint := filter.GetHint(filter.ErrorCodeUnexpectedToken, "^", tc.query, tc.position)

			require.NotEmpty(t, hint)
			assert.Contains(t, hint, tc.hintSubstring)
		})
	}
}

// TestHints_FormatDiagnosticStructure verifies the overall structure of diagnostic output.
func TestHints_FormatDiagnosticStructure(t *testing.T) {
	t.Parallel()

	parseErr := &filter.ParseError{
		Title:         "Test Error",
		Message:       "test message",
		Position:      5,
		ErrorPosition: 5,
		Query:         "test query",
		TokenLiteral:  "q",
		TokenLength:   1,
		ErrorCode:     filter.ErrorCodeMissingClosingBracket,
	}

	output := filter.FormatDiagnostic(parseErr, 0, false)

	lines := strings.Split(output, "\n")

	require.GreaterOrEqual(t, len(lines), 6, "diagnostic should have at least 6 lines")

	assert.Contains(t, lines[0], "Filter parsing error:")
	assert.Contains(t, lines[0], "Test Error")

	assert.Contains(t, lines[1], " --> ")
	assert.Contains(t, lines[1], "--filter")

	assert.Empty(t, lines[2])

	assert.Contains(t, lines[3], "test query")

	assert.Contains(t, lines[4], "^")
	assert.Contains(t, lines[4], "test message")

	assert.Empty(t, lines[5])

	assert.Contains(t, lines[6], "hint:")
}

// TestHints_FilterIndexInDiagnostic verifies filter index appears in multi-filter scenarios.
func TestHints_FilterIndexInDiagnostic(t *testing.T) {
	t.Parallel()

	parseErr := &filter.ParseError{
		Title:         "Test Error",
		Message:       "test message",
		Position:      0,
		ErrorPosition: 0,
		Query:         "bad",
		TokenLiteral:  "b",
		TokenLength:   1,
		ErrorCode:     filter.ErrorCodeUnexpectedToken,
	}

	output0 := filter.FormatDiagnostic(parseErr, 0, false)
	assert.Contains(t, output0, "--filter 'bad'")
	assert.NotContains(t, output0, "--filter[")

	output2 := filter.FormatDiagnostic(parseErr, 2, false)
	assert.Contains(t, output2, "--filter[2]")
}

// stripTimestampPrefix removes any timestamp prefix from log output.
//
// Timestamps typically appear at the start of lines in formats like:
// "2024-01-15T10:30:00Z" or "2024/01/15 10:30:00"
//
// This makes it easier to assert expected output in golden tests.
func stripTimestampPrefix(s string) string {
	timestampPattern := regexp.MustCompile(`(?m)^(\d{4}[-/]\d{2}[-/]\d{2}[T ]\d{2}:\d{2}:\d{2}[^\s]*\s+)`)
	return timestampPattern.ReplaceAllString(s, "")
}

// renderParseError parses a filter query and returns the formatted diagnostic.
// Returns an error if parsing succeeds (no error to render).
func renderParseError(query string) (string, error) {
	_, err := filter.Parse(query)
	if err == nil {
		return "", errors.New("expected parse error but got none")
	}

	var parseErr filter.ParseError
	if !errors.As(err, &parseErr) {
		return "", fmt.Errorf("expected ParseError but got: %w", err)
	}

	// Render without colors for consistent golden testing
	return filter.FormatDiagnostic(&parseErr, 0, false), nil
}
