// src/editor/extensions/__tests__/selection-validation.test.ts
import { describe, test, expect } from 'vitest'
import { EditorState, EditorSelection } from '@codemirror/state'
import { markdown, markdownLanguage } from '@codemirror/lang-markdown'
import { markdownFrontmatterField } from '../markdown-context'
import {
  isPositionInsideFrontmatterWidget,
  adjustRangeOutsideFrontmatter,
  adjustSelectionOutsideFrontmatter,
  isSelectionSafeToRestore,
  getSafeSelectionForRestore,
  getInitialCursorPosition,
  createInitialSelection,
} from '../selection-validation'

/**
 * Create an EditorState with markdown language and frontmatter field support.
 */
function createState(doc: string, selection?: EditorSelection): EditorState {
  return EditorState.create({
    doc,
    selection,
    extensions: [
      markdown({ base: markdownLanguage }),
      markdownFrontmatterField,
    ],
  })
}

const DOC_WITH_FRONTMATTER = `---
title: Test
tags: [a, b]
---

# Hello

This is content after frontmatter.
`

const DOC_WITHOUT_FRONTMATTER = `# Hello

This is a document without frontmatter.
`

describe('selection-validation', () => {
  describe('isPositionInsideFrontmatterWidget', () => {
    test('returns false for document without frontmatter', () => {
      const state = createState(DOC_WITHOUT_FRONTMATTER)
      expect(isPositionInsideFrontmatterWidget(state, 0)).toBe(false)
      expect(isPositionInsideFrontmatterWidget(state, 5)).toBe(false)
    })

    test('returns true for positions inside frontmatter range', () => {
      const state = createState(DOC_WITH_FRONTMATTER)
      // Frontmatter is "---\ntitle: Test\ntags: [a, b]\n---\n"
      // which is 33 characters (endOffset = 33)
      expect(isPositionInsideFrontmatterWidget(state, 0)).toBe(true)
      expect(isPositionInsideFrontmatterWidget(state, 10)).toBe(true)
      expect(isPositionInsideFrontmatterWidget(state, 32)).toBe(true)
    })

    test('returns false for positions at or after frontmatter endOffset', () => {
      const state = createState(DOC_WITH_FRONTMATTER)
      // endOffset is 33 (just past the closing ---\n)
      expect(isPositionInsideFrontmatterWidget(state, 33)).toBe(false)
      expect(isPositionInsideFrontmatterWidget(state, 34)).toBe(false)
      expect(isPositionInsideFrontmatterWidget(state, 50)).toBe(false)
    })
  })

  describe('adjustRangeOutsideFrontmatter', () => {
    test('returns original range for document without frontmatter', () => {
      const state = createState(DOC_WITHOUT_FRONTMATTER)
      const range = EditorSelection.range(0, 5)
      const adjusted = adjustRangeOutsideFrontmatter(state, range)
      expect(adjusted.anchor).toBe(0)
      expect(adjusted.head).toBe(5)
    })

    test('adjusts anchor inside frontmatter to endOffset', () => {
      const state = createState(DOC_WITH_FRONTMATTER)
      const range = EditorSelection.range(0, 50)
      const adjusted = adjustRangeOutsideFrontmatter(state, range)
      expect(adjusted.anchor).toBe(33) // frontmatter endOffset
      expect(adjusted.head).toBe(50)
    })

    test('adjusts head inside frontmatter to endOffset', () => {
      const state = createState(DOC_WITH_FRONTMATTER)
      const range = EditorSelection.range(50, 10)
      const adjusted = adjustRangeOutsideFrontmatter(state, range)
      expect(adjusted.anchor).toBe(50)
      expect(adjusted.head).toBe(33) // frontmatter endOffset
    })

    test('adjusts both anchor and head when both inside frontmatter', () => {
      const state = createState(DOC_WITH_FRONTMATTER)
      const range = EditorSelection.range(0, 10)
      const adjusted = adjustRangeOutsideFrontmatter(state, range)
      expect(adjusted.anchor).toBe(33)
      expect(adjusted.head).toBe(33)
    })

    test('returns original range when both outside frontmatter', () => {
      const state = createState(DOC_WITH_FRONTMATTER)
      const range = EditorSelection.range(40, 50)
      const adjusted = adjustRangeOutsideFrontmatter(state, range)
      expect(adjusted.anchor).toBe(40)
      expect(adjusted.head).toBe(50)
    })
  })

  describe('adjustSelectionOutsideFrontmatter', () => {
    test('returns original selection when no adjustment needed', () => {
      const state = createState(DOC_WITH_FRONTMATTER)
      const selection = EditorSelection.single(40)
      const adjusted = adjustSelectionOutsideFrontmatter(state, selection)
      expect(adjusted.main.anchor).toBe(40)
      expect(adjusted.main.head).toBe(40)
    })

    test('adjusts all ranges in multi-range selection', () => {
      const state = createState(DOC_WITH_FRONTMATTER)
      const selection = EditorSelection.create([
        EditorSelection.range(0, 0),
        EditorSelection.range(10, 20),
        EditorSelection.range(40, 50),
      ], 0)
      const adjusted = adjustSelectionOutsideFrontmatter(state, selection)
      // When multiple ranges adjust to the same position (33, 33),
      // EditorSelection.create merges them into a single range.
      // So we end up with 2 ranges instead of 3.
      expect(adjusted.ranges.length).toBe(2)
      expect(adjusted.ranges[0].anchor).toBe(33)
      expect(adjusted.ranges[0].head).toBe(33)
      expect(adjusted.ranges[1].anchor).toBe(40)
      expect(adjusted.ranges[1].head).toBe(50)
    })

    test('preserves mainIndex', () => {
      const state = createState(DOC_WITH_FRONTMATTER)
      const selection = EditorSelection.create([
        EditorSelection.range(0, 0),
        EditorSelection.range(40, 50),
      ], 1)
      const adjusted = adjustSelectionOutsideFrontmatter(state, selection)
      expect(adjusted.mainIndex).toBe(1)
    })

    test('returns the selection unchanged for a document without frontmatter', () => {
      const state = createState(DOC_WITHOUT_FRONTMATTER)
      const selection = EditorSelection.create([
        EditorSelection.range(2, 4),
        EditorSelection.range(10, 20),
      ], 1)
      const adjusted = adjustSelectionOutsideFrontmatter(state, selection)
      expect(adjusted).toBe(selection)
    })
  })

  describe('isSelectionSafeToRestore', () => {
    test('returns true for safe selection', () => {
      const state = createState(DOC_WITH_FRONTMATTER)
      const selection = EditorSelection.single(40)
      expect(isSelectionSafeToRestore(state, selection)).toBe(true)
    })

    test('returns false for selection inside frontmatter', () => {
      const state = createState(DOC_WITH_FRONTMATTER)
      const selection = EditorSelection.single(10)
      expect(isSelectionSafeToRestore(state, selection)).toBe(false)
    })

    test('returns false for selection with out-of-bounds positions', () => {
      const state = createState(DOC_WITH_FRONTMATTER)
      const docLen = state.doc.length
      const selection = EditorSelection.single(docLen + 100)
      expect(isSelectionSafeToRestore(state, selection)).toBe(false)
    })

    test('returns false for negative positions', () => {
      const state = createState(DOC_WITH_FRONTMATTER)
      // Create a mock selection with negative position (shouldn't happen normally)
      const selection = EditorSelection.create([
        EditorSelection.range(-1, 10),
      ])
      expect(isSelectionSafeToRestore(state, selection)).toBe(false)
    })

    test('treats a document without frontmatter as safe from offset zero', () => {
      const state = createState(DOC_WITHOUT_FRONTMATTER)
      const selection = EditorSelection.single(5)
      expect(isSelectionSafeToRestore(state, selection)).toBe(true)
    })
  })

  describe('getSafeSelectionForRestore', () => {
    test('returns original selection when already safe', () => {
      const state = createState(DOC_WITH_FRONTMATTER)
      const selection = EditorSelection.single(40)
      const safe = getSafeSelectionForRestore(state, selection)
      expect(safe).not.toBeNull()
      expect(safe!.main.anchor).toBe(40)
      expect(safe!.main.head).toBe(40)
    })

    test('adjusts selection inside frontmatter', () => {
      const state = createState(DOC_WITH_FRONTMATTER)
      const selection = EditorSelection.single(0)
      const safe = getSafeSelectionForRestore(state, selection)
      expect(safe).not.toBeNull()
      expect(safe!.main.anchor).toBe(33)
      expect(safe!.main.head).toBe(33)
    })

    test('clamps out-of-bounds selection to document length', () => {
      const state = createState(DOC_WITH_FRONTMATTER)
      const docLen = state.doc.length
      const selection = EditorSelection.single(docLen + 100)
      const safe = getSafeSelectionForRestore(state, selection)
      expect(safe).not.toBeNull()
      expect(safe!.main.anchor).toBe(docLen)
      expect(safe!.main.head).toBe(docLen)
    })

    test('handles selection that needs both clamping and frontmatter adjustment', () => {
      const state = createState(DOC_WITH_FRONTMATTER)
      // Create a selection with one range in frontmatter, one out of bounds
      const docLen = state.doc.length
      const selection = EditorSelection.create([
        EditorSelection.range(5, 10),
        EditorSelection.range(docLen + 50, docLen + 100),
      ], 0)
      const safe = getSafeSelectionForRestore(state, selection)
      expect(safe).not.toBeNull()
      expect(safe!.ranges[0].anchor).toBe(33) // adjusted for frontmatter
      expect(safe!.ranges[0].head).toBe(33)
      expect(safe!.ranges[1].anchor).toBe(docLen) // clamped to doc length
      expect(safe!.ranges[1].head).toBe(docLen)
    })
  })

  describe('getInitialCursorPosition', () => {
    test('returns 0 for document without frontmatter', () => {
      const state = createState(DOC_WITHOUT_FRONTMATTER)
      expect(getInitialCursorPosition(state)).toBe(0)
    })

    test('returns endOffset for document with frontmatter', () => {
      const state = createState(DOC_WITH_FRONTMATTER)
      expect(getInitialCursorPosition(state)).toBe(33)
    })
  })

  describe('createInitialSelection', () => {
    test('creates cursor at 0 for document without frontmatter', () => {
      const state = createState(DOC_WITHOUT_FRONTMATTER)
      const selection = createInitialSelection(state)
      expect(selection.main.anchor).toBe(0)
      expect(selection.main.head).toBe(0)
    })

    test('creates cursor after frontmatter for document with frontmatter', () => {
      const state = createState(DOC_WITH_FRONTMATTER)
      const selection = createInitialSelection(state)
      expect(selection.main.anchor).toBe(33)
      expect(selection.main.head).toBe(33)
    })

    test('creates collapsed selection (cursor, not range)', () => {
      const state = createState(DOC_WITH_FRONTMATTER)
      const selection = createInitialSelection(state)
      expect(selection.main.empty).toBe(true)
    })
  })
})