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'use strict';
const _ = {
sum: require('lodash/sum'),
flatten: require('lodash/flatten'),
};
const chalk = require('chalk');
/**
* The paginator returns a subset of the choices if the list is too long.
*/
class Paginator {
constructor(screen, options = {}) {
const { isInfinite = true } = options;
this.lastIndex = 0;
this.screen = screen;
this.isInfinite = isInfinite;
}
paginate(output, active, pageSize) {
pageSize = pageSize || 7;
let lines = output.split('\n');
if (this.screen) {
lines = this.screen.breakLines(lines);
active = _.sum(lines.map((lineParts) => lineParts.length).splice(0, active));
lines = _.flatten(lines);
}
// Make sure there's enough lines to paginate
if (lines.length <= pageSize) {
return output;
}
const visibleLines = this.isInfinite
? this.getInfiniteLines(lines, active, pageSize)
: this.getFiniteLines(lines, active, pageSize);
this.lastIndex = active;
return (
visibleLines.join('\n') +
'\n' +
chalk.dim('(Move up and down to reveal more choices)')
);
}
getInfiniteLines(lines, active, pageSize) {
if (this.pointer === undefined) {
this.pointer = 0;
}
const middleOfList = Math.floor(pageSize / 2);
// Move the pointer only when the user go down and limit it to the middle of the list
if (
this.pointer < middleOfList &&
this.lastIndex < active &&
active - this.lastIndex < pageSize
) {
this.pointer = Math.min(middleOfList, this.pointer + active - this.lastIndex);
}
// Duplicate the lines so it give an infinite list look
const infinite = _.flatten([lines, lines, lines]);
const topIndex = Math.max(0, active + lines.length - this.pointer);
return infinite.splice(topIndex, pageSize);
}
getFiniteLines(lines, active, pageSize) {
let topIndex = active - pageSize / 2;
if (topIndex < 0) {
topIndex = 0;
} else if (topIndex + pageSize > lines.length) {
topIndex = lines.length - pageSize;
}
return lines.splice(topIndex, pageSize);
}
}
module.exports = Paginator;
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