package errors

import (
	"fmt"
	"os"
	"path/filepath"

	"git.akyoto.dev/cli/q/src/build/token"
)

// Error is a compiler error at a given line and column.
type Error struct {
	Path   string
	Line   int
	Column int
	Err    error
	Stack  string
}

// New generates an error message at the current token position.
// The error message is clickable in popular editors and leads you
// directly to the faulty file at the given line and position.
func New(err error, path string, tokens []token.Token, cursor int) *Error {
	var (
		lineCount = 1
		lineStart = -1
	)

	for i := range cursor {
		if tokens[i].Kind == token.NewLine {
			lineCount++
			lineStart = int(tokens[i].Position)
		}
	}

	var column int

	if cursor < len(tokens) {
		column = tokens[cursor].Position - lineStart
	} else {
		lastToken := tokens[len(tokens)-1]
		column = lastToken.Position - lineStart + len(lastToken.Text())
	}

	return &Error{path, lineCount, column, err, Stack()}
}

// Error generates the string representation.
func (e *Error) Error() string {
	path := e.Path
	cwd, err := os.Getwd()

	if err == nil {
		relativePath, err := filepath.Rel(cwd, e.Path)

		if err == nil {
			path = relativePath
		}
	}

	return fmt.Sprintf("%s:%d:%d: %s\n\n%s", path, e.Line, e.Column, e.Err, e.Stack)
}

// Unwrap returns the wrapped error.
func (e *Error) Unwrap() error {
	return e.Err
}