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| 1 | namespace Syntax.Process.Printer is | |
| 2 | use Collections | |
| 3 | ||
| 4 | // One unit of pending work for the renderer: a document to lay out at a | |
| 5 | // given indent, in flat (`flat`) or broken mode. | |
| 6 | class RENDER_CMD is | |
| 7 | indent: int | |
| 8 | flat: bool | |
| 9 | doc: DOC | |
| 10 | ||
| 11 | init(indent: int, flat: bool, doc: DOC) is | |
| 12 | self.indent = indent | |
| 13 | self.flat = flat | |
| 14 | self.doc = doc | |
| 15 | si | |
| 16 | si | |
| 17 | ||
| 18 | // Renders a DOC tree to text against a column budget. | |
| 19 | // | |
| 20 | // Classic Wadler/Prettier algorithm: a worklist of RENDER_CMDs is consumed | |
| 21 | // depth-first; at each GROUP, `_fits` measures whether the group rendered | |
| 22 | // flat — together with whatever follows it on the same line — stays within | |
| 23 | // the budget, and picks flat or broken accordingly. | |
| 24 | class DOC_RENDERER is | |
| 25 | _width: int | |
| 26 | ||
| 27 | init(width: int) is | |
| 28 | _width = width | |
| 29 | si | |
| 30 | ||
| 31 | render(doc: DOC) -> string is | |
| 32 | let out = System.Text.StringBuilder() | |
| 33 | let cmds = LIST[RENDER_CMD]() | |
| 34 | ||
| 35 | cmds.add(RENDER_CMD(0, false, doc)) | |
| 36 | ||
| 37 | let pos mut = 0 | |
| 38 | ||
| 39 | while cmds.count > 0 do | |
| 40 | let c = cmds[cmds.count - 1] | |
| 41 | cmds.remove_at(cmds.count - 1) | |
| 42 | ||
| 43 | let d = c.doc | |
| 44 | ||
| 45 | if let t: DOC.TEXT = d then | |
| 46 | out.append(t.text) | |
| 47 | pos = pos + t.text.length | |
| 48 | fi | |
| 49 | ||
| 50 | if let concat: DOC.CONCAT = d then | |
| 51 | let i mut = concat.items.count - 1 | |
| 52 | while i >= 0 do | |
| 53 | cmds.add(RENDER_CMD(c.indent, c.flat, concat.items[i])) | |
| 54 | i = i - 1 | |
| 55 | od | |
| 56 | fi | |
| 57 | ||
| 58 | if let nest: DOC.NEST = d then | |
| 59 | cmds.add(RENDER_CMD(c.indent + nest.indent, c.flat, nest.doc)) | |
| 60 | fi | |
| 61 | ||
| 62 | if let group: DOC.GROUP = d then | |
| 63 | let flat mut = c.flat | |
| 64 | if !flat then | |
| 65 | flat = _fits(_width - pos, c.indent, group.doc, cmds) | |
| 66 | fi | |
| 67 | cmds.add(RENDER_CMD(c.indent, flat, group.doc)) | |
| 68 | fi | |
| 69 | ||
| 70 | if isa DOC.LINE(d) then | |
| 71 | if c.flat then | |
| 72 | out.append(' ') | |
| 73 | pos = pos + 1 | |
| 74 | else | |
| 75 | pos = _newline(out, c.indent) | |
| 76 | fi | |
| 77 | fi | |
| 78 | ||
| 79 | if isa DOC.SOFT_LINE(d) then | |
| 80 | if !c.flat then | |
| 81 | pos = _newline(out, c.indent) | |
| 82 | fi | |
| 83 | fi | |
| 84 | ||
| 85 | if isa DOC.HARD_LINE(d) then | |
| 86 | pos = _newline(out, c.indent) | |
| 87 | fi | |
| 88 | od | |
| 89 | ||
| 90 | return out.to_string() | |
| 91 | si | |
| 92 | ||
| 93 | _newline(out: System.Text.StringBuilder, indent: int) -> int is | |
| 94 | out.append('\n') | |
| 95 | ||
| 96 | let i mut = 0 | |
| 97 | while i < indent do | |
| 98 | out.append(' ') | |
| 99 | i = i + 1 | |
| 100 | od | |
| 101 | ||
| 102 | return indent | |
| 103 | si | |
| 104 | ||
| 105 | // True if `doc` rendered flat, plus everything queued in `rest` up to | |
| 106 | // the next break, stays within `width` columns. A HARD_LINE inside | |
| 107 | // `doc` returns false so any group containing a forced break is laid | |
| 108 | // out broken; a break reached in `rest` ends the line and returns true. | |
| 109 | _fits(width: int, indent: int, doc: DOC, rest: LIST[RENDER_CMD]) -> bool is | |
| 110 | let remaining mut = width | |
| 111 | ||
| 112 | let local = LIST[RENDER_CMD]() | |
| 113 | local.add(RENDER_CMD(indent, true, doc)) | |
| 114 | ||
| 115 | while local.count > 0 do | |
| 116 | if remaining < 0 then | |
| 117 | return false | |
| 118 | fi | |
| 119 | ||
| 120 | let c = local[local.count - 1] | |
| 121 | local.remove_at(local.count - 1) | |
| 122 | ||
| 123 | let d = c.doc | |
| 124 | ||
| 125 | if let t: DOC.TEXT = d then | |
| 126 | remaining = remaining - t.text.length | |
| 127 | fi | |
| 128 | ||
| 129 | if let concat: DOC.CONCAT = d then | |
| 130 | let i mut = concat.items.count - 1 | |
| 131 | while i >= 0 do | |
| 132 | local.add(RENDER_CMD(c.indent, true, concat.items[i])) | |
| 133 | i = i - 1 | |
| 134 | od | |
| 135 | fi | |
| 136 | ||
| 137 | if let nest: DOC.NEST = d then | |
| 138 | local.add(RENDER_CMD(c.indent + nest.indent, true, nest.doc)) | |
| 139 | fi | |
| 140 | ||
| 141 | if let group: DOC.GROUP = d then | |
| 142 | local.add(RENDER_CMD(c.indent, true, group.doc)) | |
| 143 | fi | |
| 144 | ||
| 145 | if isa DOC.LINE(d) then | |
| 146 | remaining = remaining - 1 | |
| 147 | fi | |
| 148 | ||
| 149 | if isa DOC.HARD_LINE(d) then | |
| 150 | return false | |
| 151 | fi | |
| 152 | od | |
| 153 | ||
| 154 | let rest_index mut = rest.count - 1 | |
| 155 | let pending = LIST[RENDER_CMD]() | |
| 156 | ||
| 157 | do | |
| 158 | if remaining < 0 then | |
| 159 | return false | |
| 160 | fi | |
| 161 | ||
| 162 | if pending.count == 0 /\ rest_index < 0 then | |
| 163 | return true | |
| 164 | fi | |
| 165 | ||
| 166 | let c = | |
| 167 | if pending.count > 0 then | |
| 168 | pending[pending.count - 1] | |
| 169 | else | |
| 170 | rest[rest_index] | |
| 171 | fi | |
| 172 | ||
| 173 | if pending.count > 0 then | |
| 174 | pending.remove_at(pending.count - 1) | |
| 175 | else | |
| 176 | rest_index = rest_index - 1 | |
| 177 | fi | |
| 178 | ||
| 179 | let d = c.doc | |
| 180 | ||
| 181 | if let t: DOC.TEXT = d then | |
| 182 | remaining = remaining - t.text.length | |
| 183 | fi | |
| 184 | ||
| 185 | if let concat: DOC.CONCAT = d then | |
| 186 | let i mut = concat.items.count - 1 | |
| 187 | while i >= 0 do | |
| 188 | pending.add(RENDER_CMD(c.indent, c.flat, concat.items[i])) | |
| 189 | i = i - 1 | |
| 190 | od | |
| 191 | fi | |
| 192 | ||
| 193 | if let nest: DOC.NEST = d then | |
| 194 | pending.add(RENDER_CMD(c.indent + nest.indent, c.flat, nest.doc)) | |
| 195 | fi | |
| 196 | ||
| 197 | if let group: DOC.GROUP = d then | |
| 198 | pending.add(RENDER_CMD(c.indent, c.flat, group.doc)) | |
| 199 | fi | |
| 200 | ||
| 201 | if isa DOC.LINE(d) then | |
| 202 | if c.flat then | |
| 203 | remaining = remaining - 1 | |
| 204 | else | |
| 205 | return true | |
| 206 | fi | |
| 207 | fi | |
| 208 | ||
| 209 | if isa DOC.SOFT_LINE(d) then | |
| 210 | if !c.flat then | |
| 211 | return true | |
| 212 | fi | |
| 213 | fi | |
| 214 | ||
| 215 | if isa DOC.HARD_LINE(d) then | |
| 216 | return true | |
| 217 | fi | |
| 218 | od | |
| 219 | si | |
| 220 | si | |
| 221 | si |