Gim/internal/textobject/delimiter.go

package textobject

import (
	"fmt"
	"slices"

	"git.gophernest.net/azpect/TextEditor/internal/action"
	"git.gophernest.net/azpect/TextEditor/internal/core"
)

// Map opposite char
var DirectionalDelimiterMap map[rune]rune = map[rune]rune{
	'(': ')',
	'[': ']',
	'{': '}',
	'<': '>',
}

var singleDelimiterList []rune = []rune{'"', '\'', '`'}

func getStartDelimiterFromEnd(d rune) (rune, bool) {
	if slices.Contains(singleDelimiterList, d) {
		return d, true
	}

	for start, end := range DirectionalDelimiterMap {
		if end == d {
			return start, true
		}
	}

	return ' ', false
}

func getEndDelimiterFromStart(d rune) (rune, bool) {
	if slices.Contains(singleDelimiterList, d) {
		return d, true
	}

	end, found := DirectionalDelimiterMap[d]
	return end, found
}

// Delimiter implements text object for words (iw/aw)
type Delimiter struct {
	Char rune
}

// TODO: This should allow for many lines, not just a single line
func (to Delimiter) GetRange(m action.Model, cursor core.Position, modifier string) (core.Position, core.Position, core.MotionType) {
	buf := m.ActiveBuffer()
	line := buf.Lines[cursor.Line]

	// Determine which is a starting delimiter and which ends
	_, isStartingDelimiter := DirectionalDelimiterMap[to.Char]
	var (
		startDelim rune
		endDelim   rune
		startFound bool = true
		endFound   bool = true
	)

	if isStartingDelimiter {
		startDelim = to.Char
		endDelim, endFound = getEndDelimiterFromStart(to.Char)
	} else {
		endDelim = to.Char
		startDelim, startFound = getStartDelimiterFromEnd(to.Char)
	}

	if !endFound || !startFound {
		m.SetCommandOutput(&core.CommandOutput{
			Lines:   []string{fmt.Sprintf("Could not find delimiters from '%c'", to.Char)},
			Inline:  true,
			IsError: false,
		})
		return cursor, cursor, core.CharwiseExclusive
	}

	// Try to find delimiters around the cursor position
	start, end, found := findDelimiterPair(line, startDelim, endDelim, cursor.Col, modifier == "a")

	if !found {
		return cursor, cursor, core.CharwiseExclusive
	}

	// This happens when nothing is between the delimiter
	if start.Col > end.Col {
		return cursor, cursor, core.CharwiseExclusive
	}

	// Delimiter objects don't span lines (for now)
	start.Line = cursor.Line
	end.Line = cursor.Line

	return start, end, core.CharwiseInclusive
}

func findDelimiterStart(line string, delimiter rune, col int, includeDelimiter bool) (core.Position, bool) {
	for i := col; i >= 0; i-- {
		if rune(line[i]) == delimiter {
			if includeDelimiter {
				return core.Position{Line: 0, Col: i}, true
			}
			return core.Position{Line: 0, Col: i + 1}, true
		}
	}
	return core.Position{Line: 0, Col: 0}, false
}

func findDelimiterEnd(line string, delimiter rune, col int, includeDelimiter bool) (core.Position, bool) {
	for i := col; i < len(line); i++ {
		if rune(line[i]) == delimiter {
			if includeDelimiter {
				return core.Position{Line: 0, Col: i}, true
			}
			return core.Position{Line: 0, Col: i - 1}, true
		}
	}
	return core.Position{Line: 0, Col: 0}, false
}

// findDelimiterPair tries to find a matching pair of delimiters.
// First it tries to find delimiters around the cursor.
// If that fails, it searches forward for the next pair.
func findDelimiterPair(line string, startDelim, endDelim rune, cursorCol int, includeDelimiters bool) (core.Position, core.Position, bool) {
	// First, try to find delimiters around cursor
	start, sOk := findDelimiterStart(line, startDelim, cursorCol, includeDelimiters)
	end, eOk := findDelimiterEnd(line, endDelim, cursorCol, includeDelimiters)

	if sOk && eOk {
		// Verify this is actually a valid pair by checking there are no
		// unmatched delimiters between start and end
		var startDelimPos, endDelimPos int
		if includeDelimiters {
			startDelimPos = start.Col
			endDelimPos = end.Col
		} else {
			startDelimPos = start.Col - 1
			endDelimPos = end.Col + 1
		}

		// For proper pair validation, check if this is the nearest matching pair
		// by ensuring the end delimiter we found is the first one after the start
		if isValidPair(line, startDelim, endDelim, startDelimPos, endDelimPos) {
			// Cursor should be at or between the delimiters
			if startDelimPos <= cursorCol && cursorCol <= endDelimPos {
				return start, end, true
			}
		}
	}

	// Not inside delimiters, search forward for next pair
	startDelimPos, foundStart := findNextDelimiter(line, startDelim, cursorCol)
	if !foundStart {
		return core.Position{}, core.Position{}, false
	}

	endDelimPos, foundEnd := findNextDelimiter(line, endDelim, startDelimPos+1)
	if !foundEnd {
		return core.Position{}, core.Position{}, false
	}

	// Validate this pair as well
	if !isValidPair(line, startDelim, endDelim, startDelimPos, endDelimPos) {
		return core.Position{}, core.Position{}, false
	}

	// Calculate start and end positions based on modifier
	if includeDelimiters {
		start = core.Position{Line: 0, Col: startDelimPos}
		end = core.Position{Line: 0, Col: endDelimPos}
	} else {
		start = core.Position{Line: 0, Col: startDelimPos + 1}
		end = core.Position{Line: 0, Col: endDelimPos - 1}
	}

	return start, end, true
}

// isValidPair checks if the delimiters at startPos and endPos form a valid matching pair.
// For same-delimiter pairs (quotes), it checks they form an opening/closing pair.
// For directional pairs (parens, brackets), it ensures the end is the matching closer for the start.
func isValidPair(line string, startDelim, endDelim rune, startPos, endPos int) bool {
	if startPos >= endPos {
		return false
	}

	// For quote-like delimiters where start and end are the same
	if startDelim == endDelim {
		// For quotes, we need to determine if startPos is an opening quote and endPos is a closing quote
		// We do this by counting quotes before each position
		// An opening quote has an even number of quotes before it (0, 2, 4, ...)
		// A closing quote has an odd number of quotes before it (1, 3, 5, ...)

		quotesBeforeStart := 0
		for i := 0; i < startPos; i++ {
			if rune(line[i]) == startDelim {
				quotesBeforeStart++
			}
		}

		quotesBeforeEnd := quotesBeforeStart + 1 // We know there's at least the startPos quote
		for i := startPos + 1; i < endPos; i++ {
			if rune(line[i]) == startDelim {
				quotesBeforeEnd++
			}
		}

		// startPos should be an opening quote (even number before it)
		// endPos should be a closing quote (odd number before it)
		// AND there should be no quotes between them for a simple pair
		startIsOpening := quotesBeforeStart%2 == 0
		endIsClosing := quotesBeforeEnd%2 == 1
		noQuotesBetween := quotesBeforeEnd == quotesBeforeStart+1

		return startIsOpening && endIsClosing && noQuotesBetween
	}

	// For directional delimiters, check that endPos has the first unmatched closing delimiter
	// Simple approach: ensure there's no end delimiter between startPos and endPos that would
	// close an earlier start delimiter
	nestLevel := 0
	for i := startPos + 1; i < endPos; i++ {
		if rune(line[i]) == startDelim {
			nestLevel++
		} else if rune(line[i]) == endDelim {
			if nestLevel > 0 {
				nestLevel--
			} else {
				// Found an unmatched end delimiter before our endPos
				return false
			}
		}
	}

	// The endPos should close the startPos
	return nestLevel == 0
}

// findNextDelimiter searches forward from startCol for the next occurrence of delimiter
func findNextDelimiter(line string, delimiter rune, startCol int) (int, bool) {
	for i := startCol; i < len(line); i++ {
		if rune(line[i]) == delimiter {
			return i, true
		}
	}
	return 0, false
}