// CodeMirror, copyright (c) by Marijn Haverbeke and others
// Distributed under an MIT license: https://codemirror.net/LICENSE

// Utility function that allows modes to be combined. The mode given
// as the base argument takes care of most of the normal mode
// functionality, but a second (typically simple) mode is used, which
// can override the style of text. Both modes get to parse all of the
// text, but when both assign a non-null style to a piece of code, the
// overlay wins, unless the combine argument was true and not overridden,
// or state.overlay.combineTokens was true, in which case the styles are
// combined.

;(function (mod) {
    if (typeof exports == 'object' && typeof module == 'object')
        // CommonJS
        mod(require('../../lib/codemirror'))
    else if (typeof define == 'function' && define.amd)
        // AMD
        define(['../../lib/codemirror'], mod)
    // Plain browser env
    else mod(CodeMirror)
})(function (CodeMirror) {
    'use strict'

    CodeMirror.overlayMode = function (base, overlay, combine) {
        return {
            startState: function () {
                return {
                    base: CodeMirror.startState(base),
                    overlay: CodeMirror.startState(overlay),
                    basePos: 0,
                    baseCur: null,
                    overlayPos: 0,
                    overlayCur: null,
                    streamSeen: null,
                }
            },
            copyState: function (state) {
                return {
                    base: CodeMirror.copyState(base, state.base),
                    overlay: CodeMirror.copyState(overlay, state.overlay),
                    basePos: state.basePos,
                    baseCur: null,
                    overlayPos: state.overlayPos,
                    overlayCur: null,
                }
            },

            token: function (stream, state) {
                if (stream != state.streamSeen || Math.min(state.basePos, state.overlayPos) < stream.start) {
                    state.streamSeen = stream
                    state.basePos = state.overlayPos = stream.start
                }

                if (stream.start == state.basePos) {
                    state.baseCur = base.token(stream, state.base)
                    state.basePos = stream.pos
                }
                if (stream.start == state.overlayPos) {
                    stream.pos = stream.start
                    state.overlayCur = overlay.token(stream, state.overlay)
                    state.overlayPos = stream.pos
                }
                stream.pos = Math.min(state.basePos, state.overlayPos)

                // state.overlay.combineTokens always takes precedence over combine,
                // unless set to null
                if (state.overlayCur == null) return state.baseCur
                else if ((state.baseCur != null && state.overlay.combineTokens) || (combine && state.overlay.combineTokens == null)) return state.baseCur + ' ' + state.overlayCur
                else return state.overlayCur
            },

            indent:
                base.indent &&
                function (state, textAfter, line) {
                    return base.indent(state.base, textAfter, line)
                },
            electricChars: base.electricChars,

            innerMode: function (state) {
                return { state: state.base, mode: base }
            },

            blankLine: function (state) {
                var baseToken, overlayToken
                if (base.blankLine) baseToken = base.blankLine(state.base)
                if (overlay.blankLine) overlayToken = overlay.blankLine(state.overlay)

                return overlayToken == null ? baseToken : combine && baseToken != null ? baseToken + ' ' + overlayToken : overlayToken
            },
        }
    }
})